Fariba Kohanpour
email: fariba.kohanpour@uwa.edu.au

Sandra Occhipinti

Mark Douglas Lindsay

Weronika Gorczyk

Fred Jourdan

Marc Poujol

Mineral systems prospectivity modelling for gold and nickel in the Halls Creek Orogen, Western Australia

Keywords: Mineral systems, Nd isotopic map, GIS prospectivity, age of gold mineralisation, Halls Creek Orogen

Introduction

The mineral system concept emerged two decades ago as a targeting tool for mineral exploration [START_REF] Wyborn | Australian Proterozoic mineral systems: essential ingredients and mappable criteria[END_REF]. Mineral system analysis focusses on the critical geological processes that control the generation and preservation of mineral deposits [START_REF] Blewett | Scale-integrated architecture of a world-class gold mineral system: The Archaean eastern Yilgarn Craton[END_REF][START_REF] Knox-Robinson | Towards a holistic exploration strategy: Using Geographic Information Systems as a tool to enhance exploration[END_REF][START_REF] Mccuaig | Translating the mineral systems approach into an effective exploration targeting system[END_REF][START_REF] Mccuaig | The mineral system concept: the key to exploration targeting[END_REF][START_REF] Occhipinti | Multicommodity mineral systems analysis highlighting mineral prospectivity in the Halls Creek Orogen[END_REF][START_REF] Wyborn | Australian Proterozoic mineral systems: essential ingredients and mappable criteria[END_REF]. Perspectivity mapping has arisen from mineral systems analysis [START_REF] Dulfer | Potential for Intrusion-hosted Ni-Cu-PGE Sulfide Deposits in Australia: A Continental-scale Analysis of Mineral System Prospectivity[END_REF][START_REF] Joly | Mineral Systems Analysis of the West Musgrave Province: Regional Structure and Prospectivity Modelling[END_REF][START_REF] Joly | Exploration targeting for orogenic gold deposits in the Granites-Tanami Orogen: Mineral system analysis, targeting model and prospectivity analysis[END_REF]Lindsay et al., 2016a;[START_REF] Occhipinti | Multicommodity mineral systems analysis highlighting mineral prospectivity in the Halls Creek Orogen[END_REF] as a result of increased availability of large-scale geophysical datasets, and a greater understanding of the Earth evolution and geodynamics [START_REF] Mccuaig | The mineral system concept: the key to exploration targeting[END_REF], and advances in geographical information system (GIS) technologies.

The purpose of this paper is to identify and review the mineral system components of orthomagmatic nickel sulfide and orogenic gold mineralization in the Halls Creek Orogen and applying them in prospectivity modelling. The mineral system framework applied by Occhipinti et al. (2016), presented the practical critical elements including the lithospheric architecture, geodynamic throttle, fertility, depositional site, and preservation required for ore formation and preservation. In order to complete exploration targeting, the proxies for the mineral system parameters can be mapped from geoscience datasets, which then are statistically examined by GIS-based analysis [START_REF] Bonham-Carter | Geographic information systems for geoscientists : modelling with GIS, Kidlington[END_REF][START_REF] Carranza | Geochemical anomaly and mineral prospectivity mapping in GIS[END_REF][START_REF] Kreuzer | A continent-wide study of Australia's uranium potential: Part I: GIS-assisted manual prospectivity analysis[END_REF][START_REF] Porwal | Introduction to the Special Issue: GIS-based mineral potential modelling and geological data analyses for mineral exploration[END_REF][START_REF] Porwal | Artificial Neural Networks for Mineral-Potential Mapping: A Case Study from Aravalli Province[END_REF]. This allows prioritization of critical components for prospectivity analysis at a variety of scales [START_REF] Mccuaig | Translating the mineral systems approach into an effective exploration targeting system[END_REF]. The results include a series of predictor maps for each mineral system component which are combined to estimate overall mineral potential across a region [START_REF] Joly | Mineral Systems Analysis of the West Musgrave Province: Regional Structure and Prospectivity Modelling[END_REF][START_REF] Occhipinti | Multicommodity mineral systems analysis highlighting mineral prospectivity in the Halls Creek Orogen[END_REF].

The Halls Creek Orogen tectonic evolution includes alternating periods of extension and compression [START_REF] Griffin | Tectonic implications of Palaeoproterozoic post-collisional, high-K felsic igneous rocks from the Kimberley region of northwestern Australia[END_REF]Sheppard et al., 1999a;[START_REF] Kohanpour | Examining tectonic scenarios using geodynamic numerical modelling: Halls Creek Orogen[END_REF] and is considered to represent an accretionary orogen. As accretionary orogens and convergent margins are sites of complex alternating extensional and compressional regimes favourable to the development of gold and nickel mineral systems [START_REF] Hronsky | A unified model for gold mineralisation in accretionary orogens and implications for regional-scale exploration targeting methods[END_REF]Huston et al., 2016 and herein references), it is necessary to constrain the timing of tectonic events associated with nickel and gold mineralisation in the evolution of the Halls Creek Orogen. In this study, Ar-Ar and Sm-Nd isotopic data are used to fill the gap in understanding the timing of mineralization and track the juvenile fertile zones in space and time for both nickel and gold mineral systems.

Age dating by the 40 Ar/ 39 Ar method on K-bearing minerals has been applied to some mineral deposits with a particular focus on gold deposits that have no direct links to the intrusive rocks for the application of U-Pb dating method [START_REF] Bierlein | A geochronological framework for orogenic gold mineralisation in central Victoria[END_REF][START_REF] Foster | Chronology and tectonic framework of turbidite-hosted gold deposits in the Western Lachlan Fold Belt, Victoria: 40 Ar -39 Ar results[END_REF]. The 40 Ar/ 39 Ar method shows the time at which the K-bearing minerals cooled through a specific temperature interval [START_REF] Kirkland | Reading deep time: radiogenic isotope geochronology: Geological Survey of Western Australia[END_REF]. The muscovite 40 Ar/ 39 Ar age indicates the time at which the region cooled from peak metamorphism through the muscovite closure temperature (c. 425 ± 70°C for a cooling rate of 10°C/Ma; 2σ; recalculated by [START_REF] Scibiorski | Rapid cooling and exhumation in the western part of the Mesoproterozoic Albany-Fraser Orogen[END_REF] using Monte Carlo simulations applied to the diffusion coefficients measured by [START_REF] Harrison | Diffusion of 40 Ar in muscovite[END_REF] on crystals with similar dimension as investigated in this study. This is found to overlap with known orogenic gold mineralization that forms at greenschist facies (c. 300-450°C) to lower amphibolite facies (c. <550 °C) [START_REF] Groves | The crustal continuum model for late-Archaean lode-gold deposits of the Yilgarn Block[END_REF][START_REF] Groves | Orogenic gold deposits: A proposed classification in the context of their crustal distribution and relationship to other gold deposit types[END_REF][START_REF] Tomkins | On the source of orogenic gold[END_REF]. Potassium metasomatism is also well documented to occur during Au mineralization (e.g. [START_REF] Phillips | Formation of gold deposits: Review and evaluation of the continuum model[END_REF][START_REF] Rice | Age and geologic setting of quartz vein-hosted gold mineralization at Curraghinalt, Northern Ireland; implications for genesis and classification[END_REF][START_REF] Saunders | Potassic and sodic alteration accompanying gold mineralization in the Rattling Brook Deposit, western White Bay, Newfoundland Appalachians[END_REF][START_REF] Wilson | The Ridgeway gold-copper deposit: A high-grade alkalic porphyry deposit in the Lachlan fold belt[END_REF], resulting in the crystallization of K feldspar, muscovite, sericite, and biotite. Thus the age of the muscovite may reflect the age of the hydrothermal process associated with gold mineralization.

The isotopic information also provides a constraint on the timing and nature of the source rock (i.e. juvenile or recycled), and hence on crustal growth [START_REF] Champion | Geodynamics: using geochemistry and isotopic signatures of granites to aid mineral systems studies: an example from the Yilgarn Craton: Geoscience Australia[END_REF][START_REF] Champion | Geochemistry and Nd isotope systematics of Archaean granites of the Eastern Goldfields, Yilgarn Craton, Australia: implications for crustal growth processes[END_REF][START_REF] Griffin | Archean crustal evolution in the northern Yilgarn Craton: U-Pb and Hfisotope evidence from detrital zircons[END_REF][START_REF] Huston | Tectonic Controls on the Endowment of Neoarchean Cratons in Volcanic-Hosted Massive Sulfide Deposits: Evidence from Lead and Neodymium Isotopes[END_REF]. One important isotopic system commonly used in studies of granites and related rocks is Sm-Nd, which provides a proxy for the source and model ages of the crustal blocks that magmatic rocks occur within by looking at the secular and geographical changes of isotopic signatures [START_REF] Champion | Neodymium depleted mantle model age map of Australia: explanatory notes and user guide[END_REF]. The Sm-Nd system was successfully used in the Yilgarn Craton, Western Australia to delineate crustal domains and their relationships with mineralisation [START_REF] Cassidy | Crustal evolution constraints on the metallogeny of the Yilgarn Craton[END_REF][START_REF] Huston | Tectonic Controls on the Endowment of Neoarchean Cratons in Volcanic-Hosted Massive Sulfide Deposits: Evidence from Lead and Neodymium Isotopes[END_REF][START_REF] Mole | Archean komatiite volcanism controlled by the evolution of early continents[END_REF]. The 'juvenile' and 'evolved' concepts in reference to the isotopic source refer to more radiogenic or positive ɛNd, and less radiogenic or negative ɛNd [START_REF] Huston | Tectonic Controls on the Endowment of Neoarchean Cratons in Volcanic-Hosted Massive Sulfide Deposits: Evidence from Lead and Neodymium Isotopes[END_REF]. This assumption is consistent with the Nd records which show that a primitive and enriched mantle source differentiated into high Sm/Nd values reflecting a more radiogenic and depleted mantle. Low Sm/Nd values reflect a less radiogenic and thus evolved crust [START_REF] Vervoort | Evolution of the depleted mantle: Hf isotope evidence from juvenile rocks through time[END_REF]. The two-stage Nd depleted mantle model age (T 2 DM ) [START_REF] Liew | Genesis of granitoid batholiths of Peninsular Malaysia and implications for models of crustal evolution: Evidence from a Nd/Sr isotopic and U/Pb zircon study[END_REF] is used to estimate the age of a sample (as a proxy for the crust in the region) has been separated from its mantle source [START_REF] Depaolo | Neodymium isotopes in the Colorado Front Range and crust-mantle evolution in the Proterozoic[END_REF]. For granitoids derived from the melting of continental crust, the mantle model age can be explained as a mixing age of when the various components in the crustal source were separated from the mantle [START_REF] Curtis | Identifying lithospheric boundaries using magnetotellurics and Nd isotope geochemistry: An example from the Gawler Craton[END_REF]. Thus, the whole-rock Nd values can be used to identify the spatial gradients in age and composition of the deep sources of the granitoids (e.g. [START_REF] Albrecht | Effects of basement composition and age on silicic magmas across an accreted terrane-Precambrian crust boundary[END_REF][START_REF] Hildreth | Crustal contributions to arc magmatism in the Andes of Central Chile[END_REF][START_REF] Mcdowell | Nature of the crust beneath west-central Chihuahua, Mexico, based upon Sr, Nd, and Pb isotopic compositions at the Tomóchic volcanic center[END_REF].

The newly acquired data in combination with our current understanding developed from geology, geodynamics, and geophysics is used to determine the mineral system components and corresponding mappable proxies in application with GIS-based prospectivity models. The results of this study show that there is a link between nickel and gold mineral systems within the Halls Creek Orogen through marginal basin development and subsequent basin closure. Although a general conceptual framework of mineral system analysis and prospectivity modelling presented by [START_REF] Occhipinti | Multicommodity mineral systems analysis highlighting mineral prospectivity in the Halls Creek Orogen[END_REF] is followed, significant advances in scientific understanding are included: (i) a newly defined geodynamic evolution of the region [START_REF] Kohanpour | Examining tectonic scenarios using geodynamic numerical modelling: Halls Creek Orogen[END_REF][START_REF] Kohanpour | Hf isotopic fingerprinting of geodynamic settings: Integrating isotopes and numerical models[END_REF]; (ii) application of whole-rock Nd analysis as a proxy for terrane fertility for gold and nickel mineralization; and (iii) the first 40 Ar/ 39 Ar analysis of hydrothermal alteration associated with gold mineralization. The principal elements of mineral systems considered here as lithospheric architecture, geodynamic throttle, fertility, depositional sites, and preservation (Occhipinti et al., 2016), are translated to mappable criteria and applied to a knowledge-driven GIS-based fuzzy logic prospectivity analysis. This work addresses three main questions. (i) What are the main geological processes or critical factors that were most influential on gold and nickel endowment in the Halls Creek Orogen? (ii) Where are the prospective zones for gold and nickel mineralization within the region? (iii) Does the addition of isotopic datasets such as Sm-Nd and 40 Ar/ 39 Ar improve our understanding of mineral systems components and prospectivity analyses?

Regional geology

The Halls Creek Orogen (HCO) is a well-exposed Paleoproterozoic orogenic belt, extending along the eastern side of the Kimberley Craton margin (Fig. 1). This orogen provides insights into the collision of the Kimberley Craton with the Diamantina Craton during the amalgamation of the Nuna Supercontinent. The Halls Creek Orogen comprises three tectonostratigraphic terranes: the Western, Central, and Eastern zones [START_REF] Tyler | Are there terranes within the Lamboo Complex of the Halls Creek Orogen?[END_REF].

These terranes are separated by major fault systems. The northeast-trending Angelo-Halls Creek-Osmond fault system separated the Central and Eastern zones. The Western and Central zones are separated by the northeasterly trending Ramsay Range and Springvale faults, and the northern part of the Halls Creek Fault (Fig. 1). These three zones contain distinct Paleoproterozoic geological units and were juxtaposed by the 1870˗1850

Ma Hooper Orogeny and 1835˗1805 Ma Halls Creek Orogeny [START_REF] Griffin | Tectonic implications of Palaeoproterozoic post-collisional, high-K felsic igneous rocks from the Kimberley region of northwestern Australia[END_REF][START_REF] Griffin | Geology of the southern Halls Creek Orogen: a summary of field work in 1992[END_REF][START_REF] Tyler | Are there terranes within the Lamboo Complex of the Halls Creek Orogen?[END_REF]. The later deformation events which affect all three terranes are the c. 1000˗800 Ma Yampi Orogeny, c. 560 Ma King Leopold Orogeny, and c. 370˗300 Ma Alice Spring Orogeny.

The main lithological units of the Halls Creek Orogen are shown in Fig. 1. The Eastern Zone mainly consists of metasedimentary and metavolcanic rocks of the 1880-1840 Ma Halls Creek Group, which contains the Saunders Creek, Brim Rockhole, Biscay, and Olympio formations [START_REF] Griffin | Geology of the southern Halls Creek Orogen: a summary of field work in 1992[END_REF][START_REF] Phillips | Geology of the Eastern Zone of the Lamboo Province[END_REF]. The turbiditic metasedimentary rocks of Olympio Formation contain trachyandesitic and trachytic rocks of the 1857 ± 5 Ma Maude Headley [START_REF] Page | Geochronology of a rapid 1.85-1.86 Ga tectonic transition: Halls Creek orogen[END_REF] and 1848 ± 3 Ma Butcher Gully Members [START_REF] Blake | Geology of the Halls Creek 1:100 000 Sheet[END_REF]. It was supposed that the metasedimentary and mafic rocks of the Halls Creek Group were deposited on the margin of North Australian Craton [START_REF] Griffin | Tectonic implications of Palaeoproterozoic post-collisional, high-K felsic igneous rocks from the Kimberley region of northwestern Australia[END_REF]. The Halls Creek Group is intruded by sills of c.1855-1835 Ma Woodward Dolerite [START_REF] Griffin | Geology of the southern Halls Creek Orogen: a summary of field work in 1992[END_REF][START_REF] Phillips | Geology of the Eastern Zone of the Lamboo Province[END_REF][START_REF] Tyler | 000 sheet[END_REF].

Rocks in the Eastern Zone were metamorphosed and variably deformed to greenschist facies [START_REF] Occhipinti | Multicommodity mineral systems analysis highlighting mineral prospectivity in the Halls Creek Orogen[END_REF]. The oldest rocks in the Central Zone are the c.1865 Ma mafic volcanic and turbiditic sedimentary rocks of Tickalara Metamorphics which were metamorphosed from greenschist to granulite facies [START_REF] Tyler | Are there terranes within the Lamboo Complex of the Halls Creek Orogen?[END_REF], and intruded by the tonalite and trondhjemite of the Dougalls Suite at 1850 Ma. A sequence of folded and metamorphosed turbidites, carbonate, mafic and felsic volcaniclastic rocks of the 1845-1840 Ma Koongie Park Formation is exposed in the southern part of the Central Zone [START_REF] Tyler | Geological evolution of the Kimberley region of Western Australia[END_REF]. The 1856-1830 Ma layered mafic-ultramafic intrusions observed in the Central Zone [START_REF] Page | Geochronology of the mafic-ultramafic intrusions[END_REF]. This zone was also extensively intruded by the felsic to mafic rocks of the 1835-1805 Ma Sally Downs Supersuite during the Halls Creek Orogeny. The main components of Western Zone are the c.1870 Ma turbiditic sedimentary rocks of the Marboo Formation, c.1855 Ma Whitewater Volcanics, and 1865-1850 Ma granitic and gabbroic rocks of the Paperbark Supersuite.

Gold and nickel mineralisation

The Halls Creek Orogen hosts a variety of mineral deposits documented by [START_REF] Sanders | Mineralization of the Halls Creek Orogen, East Kimberley region Western Australia[END_REF] and [START_REF] Hassan | Mineral occurrences and exploration potential of the east Kimberley[END_REF]. The major known mineralisation styles are orogenic Au, Ni-Cu-PGE, VMS, porphyry-style Cu, REE deposits, and diamond-bearing intrusions. Metasedimentary and felsic volcanic rocks of the Halls Creek Group in the Eastern Zone contain gold deposits (Fig. 1) [START_REF] Sanders | Mineralization of the Halls Creek Orogen, East Kimberley region Western Australia[END_REF]. Gold mineralisation styles in the Eastern Zone consist of quartz-carbonate sulphide veins hosted in brittle-ductile shears (e.g. the Mount Bradley deposit), stockwork quartz veins hosted in trachyandesitic to syenitic rocks of the Butchers Gully Member (e.g. the Palm Spring deposit), and alluvial occurrences [START_REF] Sanders | Mineralization of the Halls Creek Orogen, East Kimberley region Western Australia[END_REF].

The Central Zone contains a few gold deposits in the late faults hosted by felsic volcaniclastic rocks of Koongie Park Formation, Loadstone

Monzogranite and ultramafic rocks of the Lamboo intrusion in the Nicholsons Find area [START_REF] Sanders | Mineralization of the Halls Creek Orogen, East Kimberley region Western Australia[END_REF].

Warrren (1997) suggested that gold mineralisation in the Eastern Zone was derived from the mafic volcanic rocks of the Biscay Formation, lower

Olympio Formation or alkaline volcanic rocks of the Butchers Gully and Maude Headley members and then remobilized into late faults. Tyler et al. (1998) suggested that gold mineralisation is related to low-grade metamorphism and a deformation event associated with the c. 1000-800 Ma Yampi Orogeny. [START_REF] Kohanpour | Structural controls on proterozoic nickel and gold mineral systems identified from geodynamic modelling and geophysical interpretation, east Kimberley[END_REF] established that the controlling structures are mainly attributed to the deformation events that occurred during the 1835-1805 Ma Halls Creek Orogeny plate convergence or subsequent strike-slip movement of c.1000-800 Ma Yampi Orogeny.

Significant Ni-Cu-PGE mineralisation is mainly restricted to layered mafic-ultramafic intrusions in the Central Zone of the Halls Creek Orogen [START_REF] Occhipinti | Multicommodity mineral systems analysis highlighting mineral prospectivity in the Halls Creek Orogen[END_REF][START_REF] Sanders | Mineralization of the Halls Creek Orogen, East Kimberley region Western Australia[END_REF] (Fig. 1). The 1856 ± 2 Ma Panton and 1844 ± 3 Sally Malay intrusions are understood to be the most prospective intrusion for Ni-Cu-PGE mineralisation in areas dominated by amphibolite facies rocks of Tickalara Metamorphics in the Central Zone [START_REF] Occhipinti | Multicommodity mineral systems analysis highlighting mineral prospectivity in the Halls Creek Orogen[END_REF]. The mineralised mafic-ultramafic intrusions are spatially controlled by the intersection of deep crustal structures parallel with and orthogonal to the orogeny (Lindsay et al., 2016b), suggesting these structures acted as magma conduits [START_REF] Occhipinti | Multicommodity mineral systems analysis highlighting mineral prospectivity in the Halls Creek Orogen[END_REF].

The mineralised Panton and Sally Malay intrusions are folded by deformation events associated with 1835-1805 Ma Halls Creek Orogeny; therefore, intrusions of mafic-ultramafic rocks and nickel mineralisation took place prior to the accretion of Eastern Zone to the Central Zone [START_REF] Sanders | Mineralization of the Halls Creek Orogen, East Kimberley region Western Australia[END_REF][START_REF] Kohanpour | Structural controls on proterozoic nickel and gold mineral systems identified from geodynamic modelling and geophysical interpretation, east Kimberley[END_REF].

Tectonic evolution of the Halls Creek Orogen

The tectonic evolution of the Halls Creek Orogen has been extensively investigated by chemical and isotope analysis of granites [START_REF] Griffin | Tectonic implications of Palaeoproterozoic post-collisional, high-K felsic igneous rocks from the Kimberley region of northwestern Australia[END_REF]Sheppard et al., 1999a;[START_REF] Tyler | Geological evolution of the Kimberley region of Western Australia[END_REF]. [START_REF] Griffin | Tectonic implications of Palaeoproterozoic post-collisional, high-K felsic igneous rocks from the Kimberley region of northwestern Australia[END_REF] and Sheppard et al. (1999a) considered the c.1865 Ma Tickalara Metamorphics as a key unit in the Central Zone to understand the tectonic evolution of the Halls Creek Orogen. The formation of the protholiths to the Tickalara Metamorphics have been described as either forming in (1) an oceanic island arc setting above an easterly dipping subduction outboard of Kimberley Craton; or (2) an ensialic marginal basin located at the margin of Kimberley Craton [START_REF] Griffin | Tectonic implications of Palaeoproterozoic post-collisional, high-K felsic igneous rocks from the Kimberley region of northwestern Australia[END_REF]Sheppard et al., 1999a). The mentioned ambiguity in tectonic evolution of the Halls Creek Orogen has been evaluated by geodynamic numerical modelling [START_REF] Kohanpour | Examining tectonic scenarios using geodynamic numerical modelling: Halls Creek Orogen[END_REF].

The results of numerical modelling suggest the Halls Creek Orogen formed by west-dipping subduction at the margin of the Kimberley Craton [START_REF] Kohanpour | Examining tectonic scenarios using geodynamic numerical modelling: Halls Creek Orogen[END_REF]. Using time-constrained Hf isotope ratios of zircon grains from the Halls Creek Orogen [START_REF] Kohanpour | Hf isotopic fingerprinting of geodynamic settings: Integrating isotopes and numerical models[END_REF] confirmed development of an extensional regime in the early stages of subduction, leading to the formation of a back-arc basin, which is postulated to be the tectonic setting for deposition of the precursor sedimentary and igneous rocks of the Tickalara Metamorphics. Subsequent decompression melting may have caused the intrusion of mafic-ultramafic rocks into the Halls Creek Orogen. Subduction was terminated by the collision of continental plates including the combined Western and Central zones at the margin of the Kimberley Craton with the North Australian Craton. In this model, collision resulted in compression and closure of the marginal basin. The final phase of the collision was marked by the intrusion and suturing of the North Australian and Kimberley cratons by mantle-derived magmatism (Model I in [START_REF] Kohanpour | Examining tectonic scenarios using geodynamic numerical modelling: Halls Creek Orogen[END_REF].

The Halls Creek Orogen tectonic evolution includes alternating periods of extension and compression (Fig. 2) [START_REF] Kohanpour | Examining tectonic scenarios using geodynamic numerical modelling: Halls Creek Orogen[END_REF]. The main geodynamic processes operating in the Halls Creek Orogen include crustal thinning in the early stage of subduction, whereas slab detachment and crustal thickening are the most important processes during the final stage of convergent margin settings or collisions. Therefore, the evolution of the orogen is divided into three stages: The first stage (Fig. 2a) is oceanic crust subduction which is accompanied by formation of a volcanic arc and back-arc basin. This stage involves a period of local extension and crustal thinning, accompanied by upwelling of decompression melt in the early stage of the convergence between two plates. This stage is followed by an intermediate stage (Fig. 2b) of orogeny during which the overriding plate undergoes compression due to the collision of two plates. In this phase, a switch from extension to compression occurs, accompanying with basin inversion and closure. The periods of anomalous compression and/or switch in tectonic regimes are the time when the geodynamics of the region may impose strong threshold barriers to fluid flow, resulting in a highly-organised fluid flux in the system [START_REF] Mccuaig | The mineral system concept: the key to exploration targeting[END_REF] (Fig. 2b). The final stage (Fig. 2c) of the convergent system is marked by slab detachment, relaxation of the crust, and mantle-derived syn-to postcollisional magmatism. In this study, the tectonic evolution of the Halls Creek Orogen was based on the numerical models of [START_REF] Kohanpour | Examining tectonic scenarios using geodynamic numerical modelling: Halls Creek Orogen[END_REF] after the conceptual models of Sheppard et al. (1999a) and [START_REF] Griffin | Tectonic implications of Palaeoproterozoic post-collisional, high-K felsic igneous rocks from the Kimberley region of northwestern Australia[END_REF]. Other possible scenarios which considered the Kimberely Craton to be a part of a larger North Australian Craton are not considered here, although they need to define processes led to the injection of mantle-derived melts in the evolution of the Halls Creek Orogen based on the recent isotopic data [START_REF] Kohanpour | Hf isotopic fingerprinting of geodynamic settings: Integrating isotopes and numerical models[END_REF].

Methods

Ar-Ar analysis

In this study, we used the 40 Ar/ 39 Ar dating method on muscovite from hydrothermally altered samples in gold deposits to understand the time and the corresponding metallogenic events of orogenic gold mineralization in the context of the understood tectono-thermal development of the Halls Creek Orogen. Two samples from the trachyandesite rocks at the Mount Bradley Mine and quartz-sericite alteration zone within the Nicholsons Find Mine were analysed (Fig. 3). Crossed polar photomicrographs of typical muscovite crystals from the alteration zone associated with gold deposits are presented in Fig. 3 (a-d). The Mount Bradley deposit is hosted by trachyandesitic rocks of the Butchers Gully Member dated at 1848 ± 3 Ma [START_REF] Blake | Geology of the Halls Creek 1:100 000 Sheet[END_REF]. The ore-hosting rock comprises K-feldspar, plagioclase and minor quartz. The fine-grained recrystallised muscovite flakes replace K-feldspar and plagioclase, representing textural features associated with hydrothermal muscovite [START_REF] Miller | Composition of plutonic muscovite; genetic implications[END_REF][START_REF] Gomes | Chemical zoning of muscovite from the Ervedosa granite, northern Portugal[END_REF] (Fig. 3a-b). A strongly altered sample from the marginal alteration zone close to the quartz veins of Nicholsons Find Mine shows no preservation of igneous texture. The recrystallised quartz grains and muscovite flakes are the dominant minerals of the sample (Fig. 3c-d).

Muscovite crystals ranging from 212 to 125 µm size fractions, were washed, dried and then hand-picked under a binocular microscope. Only transparent grains with less surface weathering were chosen for analysis. The selected grains were loaded into discs and irradiated for 80 hours at 1000 kw in a CLICIT (Cadmium Lined Inner Core Irradiation Tube) facility at the Oregon State University TRIGA reactor. The discs include a fully inter-calibrated FCs (Fish Canyon sanidine) standard with an age of 28.294 Ma [START_REF] Renne | Joint determination of 40K decay constants and 40Ar * /40K for the Fish Canyon sanidine standard, and improved accuracy for 40Ar/39Ar geochronology[END_REF]. The main J-value (irradiation parameter) computed from standard grains within the small pits was 0.02167360 ± 0.00001951 for the Nicholsons Find Mine sample and 0.02167360 ± 0.00001731 for Mount Bradley sample. The correction factors for interfering isotopes were ( 39 Ar/ 37 Ar) Ca = 7 × 10 -4 (±1.2%), ( 36 Ar/ 37 Ar) Ca = 2.6 × 10 -4 (±0.4%) and ( 40 Ar/ 39 Ar) K = 7.3 × 10 -4 (±12.4%) [START_REF] Renne | Some footnotes to the optimization-based calibration of the 40 Ar/ 39 Ar system[END_REF]. The criteria for the determination of plateaus are as follow: the plateau must include at least 70% of 39 Ar and should be distributed over a minimum of three consecutive steps agreeing at 95% confidence level and satisfying a probability of fit (P) at least 0.05. Plateau ages from step-heated single-grain aliquots are reported with two-sigma uncertainties. All ages are calculated the decay constants proposed by [START_REF] Renne | Joint determination of 40K decay constants and 40Ar * /40K for the Fish Canyon sanidine standard, and improved accuracy for 40Ar/39Ar geochronology[END_REF].

Sm-Nd analysis

In this study, we use whole-rock Nd isotopic data to decipher the geographical changes in isotopic signature across the Halls Creek Orogen. These data and resultant maps provide implications for juvenile and/or reworked sources of granites, as well as implications for the relations of isotopic signatures with gold and nickel mineralization. A database of Sm-Nd isotopic data for 109 samples of the Halls Creek Orogen rocks was compiled from this study, published data [START_REF] Griffin | Tectonic implications of Palaeoproterozoic post-collisional, high-K felsic igneous rocks from the Kimberley region of northwestern Australia[END_REF][START_REF] Phillips | Geology of the Eastern Zone of the Lamboo Province[END_REF][START_REF] Sheppard | High-and low-K granites and adakites at a Palaeoproterozoic plate boundary in northwestern Australia[END_REF][START_REF] Sun | Trace-element geochemical and Nd isotopic study of the mafic -ultramafic intrusions: implications for their petrogenesis and tectonic environment[END_REF], and unpublished data of Geological Survey of Western Australia online database (data source in Appendix 1). Data were compiled for a range of lithologies including felsic and mafic igneous rocks and sedimentary rocks which have reliable location details and a reasonable estimated or known magmatic age. The approach used here is different from the Champion ( 2013 interpolation with intervals based on natural breaks, i.e. intervals were calculated by the software. In addition, we used the geological maps to manually assign the calculated value or average of values of ɛNd and T 2 DM related to the mapped lithological units in the region and producing an interpreted map in Arc Map. Nd model age (T 2 DM ) and ɛNd maps, besides T 2 DM /time and ɛNd/time plots, help us to decipher the secular and spatial changes of isotopic signatures of the crustal elements and place constraints on their possible source across the Halls Creek Orogen.

GIS prospectivity modelling

Mineral prospectivity modelling is a commonly used technique in integrating diverse datasets in regional exploration targeting [START_REF] Bonham-Carter | Geographic information systems for geoscientists : modelling with GIS, Kidlington[END_REF][START_REF] Carranza | Geochemical anomaly and mineral prospectivity mapping in GIS[END_REF]. Mineral prospectivity models can be considered as mathematical functions that determine where multiple important geological features in a mineral system coincide [START_REF] Occhipinti | Multicommodity mineral systems analysis highlighting mineral prospectivity in the Halls Creek Orogen[END_REF]. Prospectivity models are generally classified into knowledge-driven and data-driven based on whether model parameters rely on geological criteria in the formation of mineral deposits or statistical relationships between the location of known mineral deposits and coincident geological features [START_REF] Porwal | Artificial Neural Networks for Mineral-Potential Mapping: A Case Study from Aravalli Province[END_REF]. The optimal method of prospectivity analysis can be selected depending on the number of known deposits in a given region, but also the quality of the data and the confidence one may have in how accurately these locations represent levels of mineralisation required by the explorer [START_REF] Occhipinti | Multicommodity mineral systems analysis highlighting mineral prospectivity in the Halls Creek Orogen[END_REF]. Knowledge-driven mineral prospectivity modelling coupled with mineral system analysis is more useful in areas with no or very few mineral deposits [START_REF] Joly | Mineral Systems Analysis of the West Musgrave Province: Regional Structure and Prospectivity Modelling[END_REF], or regions seemingly possessing a large number of data points, but which have been shown to be mis-representative of mineralisation and thus inappropriate for data-driven modelling methods (for example, Lindsay et al 2016a). Subsequently, knowledge-driven methods have been widely used in mineral prospectivity modelling in greenfield regions where mineral deposit data typically meet one or both the rejection criteria [START_REF] An | Application of fuzzy set theory to integrated mineral exploration: Can[END_REF][START_REF] Bonham-Carter | Geographic information systems for geoscientists : modelling with GIS, Kidlington[END_REF][START_REF] Carranza | Geologically Constrained Probabilistic Mapping of Gold Potential[END_REF][START_REF] D'ercole | Using fuzzy logic in a Geographic Information System environment to enhance conceptually based prospectivity analysis of Mississippi Valley-type mineralisation[END_REF][START_REF] Joly | Mineral Systems Analysis of the West Musgrave Province: Regional Structure and Prospectivity Modelling[END_REF][START_REF] Joly | Exploration targeting for orogenic gold deposits in the Granites-Tanami Orogen: Mineral system analysis, targeting model and prospectivity analysis[END_REF][START_REF] Knox-Robinson | Vectorial fuzzy logic: A novel technique for enhanced mineral prospectivity mapping, with reference to the orogenic gold mineralisation potential of the Kalgoorlie Terrane[END_REF]Lindsay et al., 2016a;[START_REF] Occhipinti | Multicommodity mineral systems analysis highlighting mineral prospectivity in the Halls Creek Orogen[END_REF].

In this study, due to: (1) the limited number of known economic deposits in the Halls Creek Orogen;

(2) the lack of confidence measures and fieldvalidated assessment of the deposit location point data and;

(3) the overarching aim of the study (translating the geological concepts into mineral systems components and prospectivity modelling), the knowledge-driven fuzzy logic approach has been used for creating mineral prospectivity maps of magmatic nickel sulfide and gold mineralisation. This approach needs an understanding of different mineral system components and their relative roles in the formation of ore deposits to define fuzzy membership values. Geodynamic evolution, geophysical and geological interpretation, and isotopic data obtained from the study area are integrated to understand mineral system components and define suitable mappable proxies (predictor maps) for all key elements important in the formation and preservation of nickel and gold deposits.

The fuzzy membership values for predictor maps are estimated from the map weights, class weights and confidence factors [START_REF] Joly | Mineral Systems Analysis of the West Musgrave Province: Regional Structure and Prospectivity Modelling[END_REF][START_REF] Occhipinti | Multicommodity mineral systems analysis highlighting mineral prospectivity in the Halls Creek Orogen[END_REF]. Map weights, class weights and confidence factors were assigned to the different predictor maps based on an understanding of different mineral systems and geological evolution of the Halls Creek Orogen. The subjectively derived fuzzy membership is a useful way of incorporating geological knowledge in the GIS-based automated methods (Lindsay et al., 2016a). Map weights are defined based on the importance of the predictor maps in mineral system analysis. Class weights indicate the spatial variations from prospective geological features, and in most cases, values are assumed to decrease linearly with distance from the object of interest to the edge of a buffer zone, a cut-off distance beyond which the influence of a feature is negligible. The buffer zone represents the maximum distance permitted to be prospective. Confidence factors were assigned to each predictor map based on its perceived ability to (1) define the appropriate component of a mineral system accurately, and (2) image the desired component in a raster/map form.

The fuzzy operators include OR, and PRODUCT used to produce mineral system components and final prospectivity maps. The fuzzy OR is a function that retains the highest value from a combination of predictor layers, and is useful when combining different layers within a component.

The fuzzy PRODUCT is a penalty-function that returns the product of several fuzzy values which are less than one. Thus, fuzzy PRODUCT provides a way to combine values without simply returning the value of a dominant layer, while strongly penalizing input areas with low-fuzzy values. These aspects of fuzzy PRODUCT led to the choice of using it to combine values from different components of mineral systems (i.e.

source, pathway, depositional traps, etc.) to model mineral prospectivity (Lindsay et al., 2016a).

The modelling followed the steps described by [START_REF] Lindsay | Mineral prospectivity of the King Leopold Orogen and Lennard Shelf: potential field analysis in the West Kimberley[END_REF] and [START_REF] Occhipinti | Multicommodity mineral systems analysis highlighting mineral prospectivity in the Halls Creek Orogen[END_REF] includes: (1) identifying mappable proxies for key components of a mineral system; (2) creating predictor maps based on the identified proxies;

(3) classifying the predictor maps and assign map weight, class weight, and confidence factor to the predictor maps; (4) generating the prospectivity models through the overlay of weighted predictor maps in fuzzy inference network to produce mineral system components maps and final prospectivity maps. The classification approaches, map weights and confidence factors are presented in Table 1. It also depicts how the predictor maps combined to create maps for the mineral system components before proceeding to the final nickel and gold prospectivity maps. All of the models were constructed in ESRI ArcToolbox, by Model Builder and can be easily modified with different weights and operators.

Results

Timing of gold mineralization

A summary of the 40 Ar/ 39 Ar results appears in Table 2 and Appendix 3. Single-grain muscovite from an altered sample in Nicholsons Find Mine yielded a plateau age of 1826 ± 5 Ma (mean square weighted deviation, MSWD = 1.59, P = 0.08). Single-grain muscovite from a trachyandesite in Mount Bradley deposit yielded a plateau age of 1838 ± 5 Ma (MSWD = 1.56, P = 0.12). Plateau ages were calculated from our samples with > 98% and 74% 39 Ar released; and the mean ages are reported with 2σ uncertainty (Fig. 3 e-f). Here we consider that the plateau ages of the muscovite crystals represent the age of hydrothermal processes typically associated with gold mineralization. The isotopic results illustrate that the gold deposit formation occurred at 1838 Ma in Mount Bradley Mine in the Eastern Zone and 1826 Ma in Nicholsons Find Mine in the Central Zone. Therefore, suggesting that gold mineralisation occurred during the early stage of 1835-1805 Ma Halls Creek Orogeny. This period corresponds to a tectonic switch from an extensional to a compressional regime which was related to basin closure [START_REF] Kohanpour | Examining tectonic scenarios using geodynamic numerical modelling: Halls Creek Orogen[END_REF].

Interpretation of the isotopic data suggests a westward migration of collision and accretion corresponding to a diachroneity in the timing of gold mineralisation between c.1838 Ma in the east to c.1826 Ma in the west. Similar interpretations have been formed from conceptual tectonic models [START_REF] Griffin | Tectonic implications of Palaeoproterozoic post-collisional, high-K felsic igneous rocks from the Kimberley region of northwestern Australia[END_REF]Sheppard et al., 1999a), geodynamic numerical modelling [START_REF] Kohanpour | Examining tectonic scenarios using geodynamic numerical modelling: Halls Creek Orogen[END_REF] and Lu/Hf data [START_REF] Kohanpour | Hf isotopic fingerprinting of geodynamic settings: Integrating isotopes and numerical models[END_REF].

Temporal and spatial patterns in Nd isotopes

The Nd isotopic signature of magmatic rocks records varying proportions of crustal melting versus juvenile mantle magma input in the Halls Creek Orogen (Figs. 4 and 5, Table 3 and Appendix 1). The full data of whole-rock Nd analysis from the samples across the Halls Creek Orogen is provided in Appendix 1, and the samples analysed for this study are presented in Table 3. Figs. 4a-b show gridded images of T 2 DM and εNd map, and Figs. 4c-d present the resulted maps from assigning the T 2 DM and εNd to the lithological units based on understanding their geological relationships (Fig. 4e) [START_REF] Griffin | Geology of the southern Halls Creek Orogen: a summary of field work in 1992[END_REF][START_REF] Tyler | Are there terranes within the Lamboo Complex of the Halls Creek Orogen?[END_REF][START_REF] Tyler | Geological evolution of the Kimberley region of Western Australia[END_REF]. The Nd signature is a function of either two end-member mixing scenarios, resulting from either the input of juvenile mantle material or reworking of an unradiogenic crustal source. Therefore, the gridded interpolation between different lithological units are not representative of isotopic signatures of major lithological units across the whole orogen, especially for the regions suffering from the lack of samples (Fig. 4a, sites A and B), and therefore, be disregarded. However, in the regions with sufficient whole-rock Nd data, the interpolation can map large-scale crustal architecture (Fig. 4a, sites C and D). The second approach which assigns the ɛNd values to each lithological unit can provide more a more accurate assessment of the possible geographical distribution of isotopic signatures across the region. The magmatic rocks that were deposited in the formed in the c.1865-1835 Ma Central Zone are dominantly crustally contaminated mantle-derived magmas resulting from lithospheric extension and upwelling of decompression melts (Fig. 2a) [START_REF] Kohanpour | Examining tectonic scenarios using geodynamic numerical modelling: Halls Creek Orogen[END_REF]. εNd values of the c.1865

Ma mafic metavolcanics of Tickalara Metamorphics vary from -0.6 to 5.69, and depleted mantle model ages for this unit are Paleoproterozoic, range from 2.4 to 1.9 Ga. The c. 1586-1830 Ma mafic-ultramafic units in the Central zone have εNd ranging from -1.13 to 4.17 (more samples with positive εNd values), and T 2 DM ranging from 2.4 to 2 Ga, suggesting that the mantle source is likely similar in age and composition to the mafic components of Tickalara Metamorphics. The collisional magmatic rocks of the 1835-1805 Ma Sally Downs Supersuite contain more evolved values of εNd (-3.21 to 1.46), and T 2 DM ages between 2.6 and 2.3 Ga, suggesting that they are derived from a combination of a late Neoarchean crustal source region and juvenile mantle magma input.

The granitic and gabbroic intrusions of the 1865-1850 Ma Paperbark Supersuite in the Western Zone have evolved εNd values ranging from -3.09

to -1.14 with depleted mantle model ages ranging from 2.6-2.5 Ga, providing evidence of melting of a pre-existing Neoarchean crustal source.

Similarly, the c.1855 Ma Whitewater Volcanics have negative εNd values (-3.9 and -4) and 2.7 Ga model ages. Interestingly, the mafic-ultramafic units of the Western Zone contain a different isotopic signature and model ages from the mafic-ultramafic units in the Central Zone. They have εNd values from -1.85 to 0.03, and T 2 DM ages ranging from 2.5 to 2.37 Ga reflecting a crustal source.

The spatial pattern of Nd model ages (T 2 DM ) across the region (Figs. 4c and 5a) highlights possible differences in the underlying crust from which the sampled lithological units were sourced. A significant change in Nd depleted mantle ages occurs in the Central Zone between the Halls Creek-Angelo and Springvale-Ramsay Range fault systems. There is a predominance of younger model ages from 2.4 to 1.9 Ga in the Central Zone, due to igneous rocks of Tickalara Metamorphics and mafic-ultramafic intrusions in this region, and also records a juvenile input. East of the Halls Creek Fault, the T 2 DM ages range from 2.76 to 2.40 Ga, suggesting that the Neoarchean crust occurs in the subsurface beneath this region. However, Paleoproterozoic model ages are also observed for some igneous rocks in the Eastern Zone, suggesting juvenile inputs during the Paleoproterozoic.

Similarly, in the Western Zone, the T 2 DM ages range from 2.69 to 2.40 Ga, consistent with the presence of Neoarchean basement in this region. In

Prospectivity models

Predictor maps

Source-Geodynamic throttle

In this study, the source component of the mineral system tied to the lithological units formed in metallogenically desirable tectonic settings during the much broader evolution of the Halls Creek Orogen. The reason for considering lithotype as a proxy for the source is that the origin of metal and fluid is connected to the processes of rocks formation. The lithological units are taken from the updated interpreted basement geological map [START_REF] Occhipinti | Multicommodity mineral systems analysis highlighting mineral prospectivity in the Halls Creek Orogen[END_REF]. A buffer zone of 1 km is considered around the lithological units. The map weights assigned to the different lithological units depend on their ability in providing metals and fluids in a particular tectonic setting.

Mafic-ultramafic units formed due to decompression mantle melting during marginal basin development (Fig. 2b) are assumed to have the greatest potential to host magmatic nickel sulfides. For example, the 1856 ± 2 Ma Panton and 1844 ± 3 Sally Malay intrusions which developed before the 1835-1805 Ma Halls Creek Orogeny. Relevant mafic-ultramafic rocks were extracted from the geological map as the source in nickel mineral system includes Sally Malay, Panton Suite, Toby gabbro, Springvale, Corridor gabbro, and Lamboo ultramafic. The highest weight of 1 was assigned to the known mineralized mafic-ultramafic units i.e. Sally Malay and Panton Suite in the Central Zone. The map weights of 0.8 and 0.7

were assigned to the other mafic-ultramafic units in the Western Zone and southern part of the Central Zone, respectively (Fig. 6a).

For the orogenic gold system, the metals and fluids are generally connected to the tectonic settings and are not considered to have any direct generic relationship to specific lithological units [START_REF] Groves | Province-scale commonalities of some world-class gold deposits: Implications for mineral exploration[END_REF]. For this reason, we considered the lithological units within the perceived tectonic settings of orogenic gold deposits as the proxies for the source component. We used the lithological units related to three major possible tectono-magmatic environments for orogenic gold deposits and include sedimentary and volcanic rocks in the back-arc setting [START_REF] Griffin | Tectonic implications of Palaeoproterozoic post-collisional, high-K felsic igneous rocks from the Kimberley region of northwestern Australia[END_REF][START_REF] Occhipinti | Multicommodity mineral systems analysis highlighting mineral prospectivity in the Halls Creek Orogen[END_REF]Sheppard et al., 1999b), i.e. the Tickalara metamorphics and Koongie Park Formation, magmatic rocks of collisional settings include felsic and mafic igneous rocks of Sally Downs Supersuite [START_REF] Sheppard | High-and low-K granites and adakites at a Palaeoproterozoic plate boundary in northwestern Australia[END_REF], and meta-volcanic and turbiditic sedimentary rocks of active margin origins [START_REF] Tyler | Geological evolution of the Kimberley region of Western Australia[END_REF] which include the Olympio and Biscay formations (Fig. 6b). The map weights of lithological units are presented in Table 1. The 'source' predictor maps were combined using the fuzzy OR operator. A map weight of 0.9 was given to the 'source' component for the final fuzzy overlay.

Lithospheric architecture

The crustal-scale architecture is considered an essential component of gold and nickel mineral systems due to the critical role of faults in the regional-scale fluid migration [START_REF] Cox | Principles of Structural Control on Permeability and Fluid Flow in Hydrothermal Systems[END_REF][START_REF] Groves | Orogenic gold deposits: A proposed classification in the context of their crustal distribution and relationship to other gold deposit types[END_REF][START_REF] Mccuaig | The mineral system concept: the key to exploration targeting[END_REF]). The regional structure interpretation by [START_REF] Kohanpour | Examining tectonic scenarios using geodynamic numerical modelling: Halls Creek Orogen[END_REF] was used as the source layer of structural features. Terrane boundaries are considered as the major mantle-tapping structures and are thus assigned the highest map weight of 1. A 10 km buffer zone is created around the terrane boundaries to simulate the potential for distal processes around the object. All major deep structures not considered to be terrane boundaries were considered during the analysis [START_REF] Kohanpour | Structural controls on proterozoic nickel and gold mineral systems identified from geodynamic modelling and geophysical interpretation, east Kimberley[END_REF] and assigned a 5 km buffer zone, as fluid pathways in the area. Major structures were divided into north-northeasterly or orogen-parallel and northwesterly cross-orogen segments. The NNE trending structures were assigned the map weight 0.8 since it considered they developed during the extensional phase of the accretionary orogen [START_REF] Kohanpour | Structural controls on proterozoic nickel and gold mineral systems identified from geodynamic modelling and geophysical interpretation, east Kimberley[END_REF]. Whereas the NW striking structures were assigned a map weight of 0.7. The classes for all the predictor maps correspond to 1 km intervals, thus the membership values decrease from the maximum value away from the structure at 1 km intervals. The reclassified distance to faults and terrane boundaries combined using the fuzzy OR operator to generate the 'lithospheric architecture' map (Fig. 7). A map weight of 0.7 was given to the 'lithospheric architecture' component.

Depositional sites

Lower order structures and geological complexities in the middle to upper crust can act as physical traps for fluid [START_REF] Breeding | Slab-derived fluids and quartz-vein formation in an accretionary prism, Otago Schist[END_REF][START_REF] Cox | Principles of Structural Control on Permeability and Fluid Flow in Hydrothermal Systems[END_REF]. Faults are prime locations for increased permeability that can trigger the fluid flow [START_REF] Cox | Principles of Structural Control on Permeability and Fluid Flow in Hydrothermal Systems[END_REF][START_REF] Micklethwaite | Active fault and shear processes and their implications for mineral deposit formation and discovery[END_REF].

Anticlinal folds axes also act as traps for mineralizing fluids [START_REF] Groves | The conjunction of factors that lead to formation of giant gold provinces and deposits in non-arc settings[END_REF][START_REF] Kohanpour | Structural controls on proterozoic nickel and gold mineral systems identified from geodynamic modelling and geophysical interpretation, east Kimberley[END_REF]. Therefore, we created predictor maps 'distance to faults' with 1 km buffer zone and 'distance to folds' with 5 km buffer zone (Fig. 8a-b) to constrain the prospectivity to a specific distance beyond which the influence is considered negligible. Fault bends can also increase fluid flow in the system and act as depositional zones [START_REF] Ford | Factors affecting fluid flow in strike-slip fault systems: coupled deformation and fluid flow modelling with application to the western Mount Isa Inlier[END_REF][START_REF] Occhipinti | Multicommodity mineral systems analysis highlighting mineral prospectivity in the Halls Creek Orogen[END_REF]. The 'faults bends' map generated by kernel density of point features representing changes in the orientation of faults (Fig. 8c). The density map of 'geological complexities' calculated as the kernel density of intersections of all line features including lithological boundaries, non-major faults and fold axes considered as a proxy for zones of localized damage and increased permeability (Fig. 8d). Lithological boundaries with high rheological and chemical reactivity contrasts are considered as preferential traps [START_REF] Brown | Artificial neural networks: a new method for mineralprospectivity mapping[END_REF] and corresponding predictor maps were created. The assigned relative rheology and chemical reactivity value of the lithological units of the Halls Creek Orogen by [START_REF] Occhipinti | Multicommodity mineral systems analysis highlighting mineral prospectivity in the Halls Creek Orogen[END_REF] was used for creating predictor maps. Lithological contacts were attributed the difference values of respective rheological and geochemical reactivity values of two adjacent units, then the kernel density of contacts with contrast values larger than zero was computed for predictor maps of 'competency contrast' and 'chemical reactivity contrast' respectively (Fig. 8e,f). The kernel density tool in ArcGIS uses a window function to represent the magnitude-per-unit area of point feature density as a property value in the resulting output raster cell.

The 'depositional sites' map for magmatic nickel sulfide was generated using a fuzzy OR operator to combine the predictor maps geological complexity, competency contrast, and chemical reactivity contrast. Each predictor map was assigned a weight of 0.8 (Fig. 9a). The 'depositional sites' map for orogenic gold was generated by combining the predictor maps distance to folds, distance to fold axes, fault bends, geological complexities, competency contrast, and chemical reactivity contrast with map weights of 0.8, 0.9, 0.9, 0.7, 0.8, and 0.8, respectively (Fig. 9b). A map weight of 0.5 was assigned to the 'depositional sites' component.

Fertility

The relationship between nickel and gold deposits and more juvenile isotopic signature in the Halls Creek Orogen is apparent in Fig. 10a, suggesting that the isotopes may record the favourable tectonic settings for this mineralization in extensional zones which characterised by fluxes of juvenile magmas. While considering the role of mantle-derived magmatism in gold and nickel mineralization [START_REF] Barnes | The mineral system approach applied to magmatic Ni-Cu-PGE sulphide deposits[END_REF][START_REF] Bleeker | Synorogenic gold mineralization in granite-greenstone terranes: the deep connection between extension, major faults, synorogenic clastic basins, magmatism, thrust inversion, and long-term preservation[END_REF][START_REF] Blewett | Scale-integrated architecture of a world-class gold mineral system: The Archaean eastern Yilgarn Craton[END_REF][START_REF] Griffin | Continental-root control on the genesis of magmatic ore deposits[END_REF][START_REF] Hronsky | A unified model for gold mineralisation in accretionary orogens and implications for regional-scale exploration targeting methods[END_REF][START_REF] Wyman | Orogenic gold and the mineral systems approach: Resolving fact, fiction and fantasy[END_REF], and the close spatial correlation between the gold and nickel mineralized region in the Halls Creek Orogen with regional positive εNd signatures, we choose rocks with more juvenile signature (i.e. more radiogenic) as the more fertile rocks in mineral systems prospectivity analysis.

The ɛNd map was used as a proxy for fertility component in prospectivity modelling. Firstly, the ɛNd map is classified based on the values of ɛNd assigned to different lithological units, with the highest class values assigned to more juvenile rock types. We assigned the class value of 3 to ɛNd values greater than 1.5, 2 to values between 0 and 1.5, 1 to values between -2.16 and 0, and 0 to values less than -2.16 (Fig. 10b). Map weights of 0.5 were given to the 'fertility' component due to lack of samples in some regions. It is noted that mineral system approach is based on a wide range of geological information, and isotopic map such as the εNd image presented in this section is just one layer that will be integrated with 'source' layer to present the lithological units that provide ore components for mineralisation.

Preservation

The preservation component is critical for some types of mineral systems, especially for those formed in the upper crust. In this study, metamorphic maps created by [START_REF] Occhipinti | Multicommodity mineral systems analysis highlighting mineral prospectivity in the Halls Creek Orogen[END_REF] were used as a proxy for preservation (Fig. 11a). The metamorphic map also presents the sharp boundaries between low/medium and high metamorphic along the major faults. The configuration of metamorphic grade of outcropping units suggests structurally controlled exhumation of fault blocks (Lindsay et al., 2016b). Magmatic nickel sulfide deposits tend to form at a wide range of crustal depths [START_REF] Barnes | The mineral system approach applied to magmatic Ni-Cu-PGE sulphide deposits[END_REF], therefore the preservation component is not used for the prospectivity model. Orogenic gold deposits are formed in crustal depths from 3 to 20 km [START_REF] Groves | The crustal continuum model for late-Archaean lode-gold deposits of the Yilgarn Block[END_REF], so preservation is an important consideration for prospectivity analysis. Based on the likelihood of gold deposits in the different metamorphic grades, we assigned the class values of 3 to 'greenschist facies', 2 to 'prehnite to greenschist facies' rocks, 1 to 'greenschist to amphibolite facies' and 'non-metamorphosed' rocks, and 0 to granulite and amphibolite rocks (Fig. 11b). A map weight of 0.5 was given to the 'preservation' component.

Fuzzy logic models

Fuzzy logic modelling is completed by combining predictor maps using an appropriate fuzzy inference network resulting in the generation of prospectivity maps. The fuzzy predictor maps of the source, lithospheric architecture, depositional sites, fertility, and preservation were first combined using the fuzzy OR operator to create a single predictor map for each critical component of gold and nickel mineral system. Finally, the fuzzy map for each component of gold and nickel mineral systems, respectively, were combined using the fuzzy PRODUCT operator to create the output prospectivity maps (Figs. 12 and 13). Details of the fuzzy inference network used are presented in Table 1.

Nickel prospectivity model-Nickel prospectivity analysis was completed taking into account rock type, fertility, connectivity to deep crustal faults, depositional sites (i.e. areas with geological complexities, high rheological and chemical reactivity contrasts). Mafic-ultramafic rocks that intruded during the extensional event prior to the Halls Creek Orogeny such as the Panton Suite, Sally Malay Suite, Toby Gabbro, Corridor Gabbro, Springvale Suite, and Lamboo ultramafic are included in this analysis. All prospective areas are within mapped mafic and ultramafic rocks.

Therefore, proximity to mafic-ultramafic rocks as a source component of the mineral system has a major influence on the prospectivity calculations (Fig. 12). The resulting prospectivity map illustrates that deposits and occurrences of nickel sulfide have been captured in the prospectivity model (Fig. 12), with the addition of other areas not currently known to contain any nickel mineralization in the south of the Central Zone.

Gold prospectivity models-Unlike the Ni prospectivity analyses, the gold prospectivity model was completed with the addition of the preservation proxy. The source proxies included rock types that are considered to be formed during the marginal basin development and subsequent basin closure and collision, connectivity to deep structures and terrane boundaries, and depositional sites i.e. areas with structural complexities, anticlinal hinge zones, and dilational jogs. The Eastern zone appears to be the most prospective area for gold mineralization, but the highly prospective zone appears focused along the Halls Creek-Angelo faults system (Fig. 13a). This fault system is a terrane boundary between the Eastern and Central zones, reactivated through time and thus it could have been the focus of fluid through the region at periods coincident with basin formation and closure. In the Eastern Zone, parts of the Biscay Formation in the regions of high structural complexities or areas around the shear zones between the major strike-slip faults are considered the most prospective regions (Fig. 13b). There is a cluster of gold deposits that are not highlighted in the prospectivity model in site A of figure 13b. This may be due to the lack of nearby mapped deep crustal-scale structures, although this area has a good potential for deposition, preservation, and source. Some high prospective regions are also located in the intersection of major deep structures, that could act as conduits for mineralizing fluids into the crust (Fig. 13c), or close to anticlinal structures for focusing the mineralizing fluids (Fig. 13c). In addition to the Eastern Zone, some areas in the Central Zone were found to be prospective for gold mineralisation. For example, in areas of greenschist facies Tickalara Metamorphics that contain favourable structural traps and are close to the deep structures (Fig. 13c). In the southern part of the Halls Creek Orogen, prospective regions coincide with juvenile isotopic signatures (Fig. 13a) derived from intrusions of Lamboo Ultramafics and Woodward Dolerite. Interestingly, many regions considered prospective for Au mineralization area in the Central Zone are in areas with no known Au mineralisation and highlight further mineral exploration opportunities.

Discussion

The prospective areas of nickel and gold mineralization modelled in the Halls Creek Orogen lie in the Central Zone and Eastern Zone and are mainly controlled by tectonic processes, which have been recognized by integrating the geodynamic model, geophysical interpretation and isotopic data from the region. Three metallogenically important tectono-magmatic environments for magmatic nickel and orogenic gold mineralisation are recognized in the Halls Creek Orogen. The first is the superimposed rift (back-arc basin) on the active convergent margin as a response to slab rollback and upwelling of mantle decompression melt. Rifting and juvenile magma input to the margin of Kimberley Craton is confirmed by a positive εNd signature in the Central Zone, whereas the evolved values resulting from reworking of Archean basement are observed in the Eastern and Western zones. A range of gold deposits and magmatic Ni sulfide deposits may form in this environment [START_REF] Barnes | The mineral system approach applied to magmatic Ni-Cu-PGE sulphide deposits[END_REF][START_REF] Hronsky | A unified model for gold mineralisation in accretionary orogens and implications for regional-scale exploration targeting methods[END_REF]. These rifts are dominated by sedimentary and magmatic rocks characterized by relatively high-temperature/low-pressure metamorphic assemblages in continental margins, as observed in the Halls Creek Orogen [START_REF] Occhipinti | Multicommodity mineral systems analysis highlighting mineral prospectivity in the Halls Creek Orogen[END_REF]. Whereas the mafic magmatic rocks locally provide the Ni and other important elements, sedimentary rocks deposited in this setting are likely to have provided a source of sulfur [START_REF] Barnes | The mineral system approach applied to magmatic Ni-Cu-PGE sulphide deposits[END_REF].

The second metallogenic environment is associated with inversion of a continental rift during a switch from extension to compression. Orogenic gold deposits can be one of the main mineralization-styles developed in this environment [START_REF] Bleeker | Synorogenic gold mineralization in granite-greenstone terranes: the deep connection between extension, major faults, synorogenic clastic basins, magmatism, thrust inversion, and long-term preservation[END_REF][START_REF] Blewett | Scale-integrated architecture of a world-class gold mineral system: The Archaean eastern Yilgarn Craton[END_REF][START_REF] Hagemann | Mineral system analysis: Quo vadis[END_REF][START_REF] Hronsky | A unified model for gold mineralisation in accretionary orogens and implications for regional-scale exploration targeting methods[END_REF][START_REF] Huston | Tectono-metallogenic systems -The place of mineral systems within tectonic evolution, with an emphasis on Australian examples[END_REF][START_REF] Wyman | Orogenic gold and the mineral systems approach: Resolving fact, fiction and fantasy[END_REF]. Basin inversion is sometimes associated with the transition from mafic mantle-derived to crustal-derived magmatism that can be synchronous with gold mineralisation [START_REF] Cassidy | Characterisation and metallogenic significance of Archaean granitoids of the Yilgarn Craton, Western Australia: Minerals and Energy Research Institute of Western Australia (MERIWA)[END_REF][START_REF] Champion | Neodymium depleted mantle model age map of Australia: explanatory notes and user guide[END_REF]Cassidy, 2007, 2008;[START_REF] Czarnota | Geodynamics of the eastern Yilgarn Craton[END_REF]. This transition is clear in the εNd values when the juvenile signatures of Tickalara Metamorphics and maficultramafic units changed to more evolved values of Sally Downs Supersite. In addition, Ar-Ar dating of gold mineralization suggests that orogenic gold deposits in the Halls Creek Orogen formed subsequent to basin formation, in the early stage of collision when closure of the marginal basin occurred.

The third major tectono-magmatic environment is characterized by upwelling of the hydrated mantle that generates bimodal volcanism during continental collision and likely triggers formation of magmatic Ni sulfide deposits [START_REF] Begg | Lithospheric, Cratonic, and Geodynamic Setting of Ni-Cu-PGE Sulfide Deposits[END_REF]. Ni-PGE mineralized mafic-ultramafic intrusions including the c. 1856 Ma Panton and c. 1845 Ma Sally Malay Suites (Hoatson, 2000) were deformed during the 1835-1805 Ma Halls Creek Orogeny [START_REF] Kohanpour | Structural controls on proterozoic nickel and gold mineral systems identified from geodynamic modelling and geophysical interpretation, east Kimberley[END_REF] suggesting that nickel mineralisation occurred prior to this event. Extensional environments are accepted as being a common setting for nickel sulfide mineralization deposition [START_REF] Begg | Lithospheric, Cratonic, and Geodynamic Setting of Ni-Cu-PGE Sulfide Deposits[END_REF][START_REF] Naldrett | Magmatic sulfide deposits: Geology, geochemistry and exploration[END_REF] providing the right conditions for moderate to high degrees of partial melting beneath continents in regions of the thinned lithosphere [START_REF] Dulfer | Potential for Intrusion-hosted Ni-Cu-PGE Sulfide Deposits in Australia: A Continental-scale Analysis of Mineral System Prospectivity[END_REF]. However, mildly compressional or transpressional conditions for Ni-PGE deposition have also been suggested by [START_REF] Begg | Lithospheric, Cratonic, and Geodynamic Setting of Ni-Cu-PGE Sulfide Deposits[END_REF]. The lack of crustal contamination and juvenile signatures (positive εNd values) of mineralised mafic-ultramafic units in the Central Zone suggest that upwelling of mantle-derived melts and crustal thinning in an extensional environment could lead to the development of nickel mineralisation in the Hall Creek Orogen. Although, the possibility of Ni-PGE mineralization in the early stage of collision when basin inversion and regional compression were dominant, cannot be disregarded as it is reported in some nickel mineralization hosted by small intrusions (Begg et al., 2010 and herein references).

Although the magmatic nickel mineral system can be directly linked to the mafic-ultramafic units in the extensional setting, the areas of highest Au prospectivity modelled in the Halls Creek Orogen cannot be directly linked to the lithological units and their corresponding tectonic settings.

In case of considering the possibility of the formation and preservation of orogenic gold deposits in amphibolite facies and granulite terranes [START_REF] Groves | Orogenic gold deposits: A proposed classification in the context of their crustal distribution and relationship to other gold deposit types[END_REF][START_REF] Lisitsin | Orogenic gold mineral systems of the Western Lachlan Orogen (Victoria) and the Hodgkinson Province (Queensland): Crustal metal sources and cryptic zones of regional fluid flow[END_REF][START_REF] Mccuaig | The nature and dimensions of regional and local gold-related hydrothermal alteration in tholeiitic metabasalts in the Norseman goldfields: the missing link in a crustal continuum of gold deposits?[END_REF][START_REF] Vielreicher | The giant Kalgoorlie Gold Field revisited[END_REF] the preservation layer can be discarded from the prospectivity modelling. In this case, the resulting prospectivity map suggests that the metamorphosed rocks of the Tickalara Metamorphics in the Central Zone which formed in the marginal (back-arc) basin appear to be the most prospective areas for orogenic gold deposits (Fig. 14a).

Furthermore, in order to understand the importance of fertility for orogenic gold targeting, we completed the prospectivity analysis without including a fertility layer. The resulting map highlights a large prospective area across the region, mainly based on the structural controls (Fig. 14b), and illustrates that addition of isotopic/geochemical data as a proxy for fertility to the prospectivity model can make a significant difference in constraining the gold prospective regions. This may be due to isotopic signatures highlighting large-scale geodynamic processes and source of magmatism involved in mineralisation. It is demonstrated that applying geochemical and/or isotopic fertility indicators can restrict the extent of the prospective areas, which is desirable for exploration targeting.

Another considered factor in the prospectivity of orogenic gold deposit is the source, which is still hotly controversial because the potential sources could be distal (hundreds of km) to the depositional sites [START_REF] Tomkins | On the source of orogenic gold[END_REF][START_REF] Groves | Province-scale commonalities of some world-class gold deposits: Implications for mineral exploration[END_REF][START_REF] Groves | The conjunction of factors that lead to formation of giant gold provinces and deposits in non-arc settings[END_REF]). To test the influence of the source layer, it was removed from prospectivity modelling. The resulting map (Fig. 14c) does not show significant changes in comparison with the main prospectivity model presented in Fig. 13. This may be due to the possibility of a wide range of lithological units as a source component for gold mineralization. It should be noted that some more small prospective regions in Western and Eastern zones appeared due to proximity to deep structures and fertility values. Although we applied a high map weight for the source layer, its contribution in the final prospectivity model is not noticeable, suggesting the significance of other mineral system components, especially fertility and structural controls in the targeting of the orogenic gold deposits.

Results for the nickel and gold prospectivity models show that the most influential critical element for the prospectivity is fertility, herein mapped using isotopic data, but previously mapped using lithological data alone [START_REF] Occhipinti | Multicommodity mineral systems analysis highlighting mineral prospectivity in the Halls Creek Orogen[END_REF]. It is demonstrated that the εNd map is a significant evidence layer that can reflect the tectono-magmatic environments of nickel and gold mineral systems. This is the case even though this critical element layer was not highly weighted in the final fuzzy overlay (Table . 1). The source which is correlated to the lithological units has a critical role for nickel mineralization, whereas it is not so influential for orogenic gold prospectivity model. Major crustal-scale shear zones and faults acting as fluid pathways and structural traps. They may play a more important role in the orogenic gold mineral system than the source component.

The process of generating a prospectivity analysis drove simultaneous consideration of the results gained from geodynamic modelling, geophysical interpretation, and isotope analysis, thus revealed links between nickel and gold mineral systems. The results also exhibit the effectiveness of the knowledge-driven GIS-based prospectivity modelling in reducing the search space for explorers (Lindsay et al., 2016). Tables 4 and5 show the reduction in search space achieved by this study. If the top three percentiles (i.e. highest 50%) of the prospectivity values are considered to be the most attractive sites for explorers, then this analysis reduced the search space to 3.2% and 2.2%

of the total of the study area for gold and nickel mineral systems, respectively. Conversely, if the lowest 50% of prospectivity values are considered unprospective, the analysis shows that approximately 95% of the study area can be ignored for gold and nickel exploration. In geographical terms, this reduces the area of the ground for further studies at camp scales to 742 km 2 for orogenic gold and 517 km 2 for magmatic nickel mineralisation from an initial study area of 23067 km 2 . Applying isotopic mapping to prospectivity modelling reduces the search space efficiently from 1583 km 2 to 742 km 2 , an improvement of almost 50%, for targeting orogenic gold deposits. However, the source component is not as effective and does not reduce the search space considerably (Table 5). The metamorphic layer, as a proxy of preservation, is moderately effective and reduces the search space from 953 km 2 to 742 km 2 , but more importantly, relocates highly prospective regions from the Central Zone to the Eastern Zone (Fig. 14a and Table 5). These results highlight how important isotopic mapping is for the techniques applied in this study. This can be extended to prospectivity modelling in general, and potential benefit isotopic data can provide in reducing the search space in greenfield regions.

Conclusions

This study has sought to develop a deeper understanding of mineral system components in the Halls Creek Orogen by applying the geodynamic numerical models, geological-geophysical interpretations, and isotopic analysis. Theoretical concepts and criteria for each of the five mineral systems components including geodynamic throttle, lithospheric architecture, fertility, depositional sites, and preservation were analyzed and evidence maps generated to best represent favourable geological processes that led to nickel and gold mineralisation. For the first time, the age of gold mineralization is determined in the Halls Creek Orogen. In addition, the whole-rock Nd analysis across the region used to produce the fertility map by applying an interpretive method rather than gridding. The resultant Nd-fertility map allowed us to employ isotopic inputs in the prospectivity analysis.

The geodynamic models and isotopic data clarify the link between major tectono-metallogenic events with nickel and gold mineralization. A better understanding of geodynamic settings and tectonic evolution has led us to a greater understanding of large-scale controls on mineral systems, which resulted in greater predictive ability. The isotopic analysis ( 40 Ar/ 39 Ar and whole-rock Nd) and deformational overprints used to determine the specific tectonic events and lithological units responsible for nickel and gold mineralisation. The lithological units developed in the metallogenically favourable geodynamic epochs provide the source component for prospectivity analysis. Furthermore, whole-rock Nd analysis provides the spatial distribution of fertilized regions, especially for the orogenic gold mineral systems that source component is not robust. The major crustal-scale faults are shown to control the regional distribution of nickel and gold deposits. Of these, terrane boundaries seem to be the most influential structures which are implied to be sites of fluid migration across the region.

The effectiveness of available datasets as proxies for the mappable criteria is an issue in any GIS-based knowledge-driven prospectivity modelling.

This has been addressed as far as possible by assigning weightings consistent with the importance and reliability of the datasets. For this reason, we used a low weight for isotopic datasets due to the irregular distribution of data across the region. It is recognized the additional geochemical and isotopic data could significantly change the assessment of prospectivity models by providing fertility indicators across the region.

Prospectivity modelling shows the most favorable areas for magmatic nickel sulfides are in the Central Zone associated with mantle-derived maficultramafic rocks that lie close to deep crustal-faults. Prospectivity modelling of orogenic gold deposits shows a strong relationship with structural traps within the mantle-derived rocks (i.e. Biscay Formation, Woodward Dolerite, and Tickalara Metamorphics) in the Eastern and Central zones with particular favorability along the Halls Creek-Angelo faults system. The results highlighted that the syn-orogenic extensional regime accompanied by upwelling of mantle-derived melts, and the following compressional regime and basin closure are the critical processes in the formation of the nickel and gold deposits.

Acknowledgment

This work is part of MRIWA Project, M465 "Deep crustal-scale structure, geological evolution, and multi-commodity analysis in the Halls Creek Orogen, Kimberley region, Western Australia". ML is supported by and ARC DECRA (DE190100431), the DARE ARC ITTC (IC190100031) and the 'MinEx' CRC. We would like to thank the Geological Survey of Western Australia, Panoramic Resource Ltd and MRIWA for their financial, field, and data support. We thank Andy Wilde and an anonymous reviewer for helpful comments. [START_REF] Occhipinti | Multicommodity mineral systems analysis highlighting mineral prospectivity in the Halls Creek Orogen[END_REF]; (b) Representative map of 'preservation' used for the final fuzzy overlay of orogenic gold prospectivity models. Fig. 12. Prospectivity map derived for magmatic nickel sulfide mineralization overlain with nickel mines, deposits and occurrences, presenting a close relationship of highly prospective areas with mafic-ultramafic units as 'source' component. Fig. 13. Prospectivity maps for orogenic gold mineralization in the Halls Creek Orogen overlain with Au deposits and mines, (a) Regional scale prospectivity map illustrating that the highest prospectivity is within the Eastern Zone; (b & c) Enlarged maps representing the relations of high prospective areas with interpreted structures from [START_REF] Kohanpour | Structural controls on proterozoic nickel and gold mineral systems identified from geodynamic modelling and geophysical interpretation, east Kimberley[END_REF] and major lithological units. Fig. 14. (a) Gold prospectivity models that consider gold deposits forming in amphibolite-granulite metamorphic conditions; (b) Prospectivity maps produced without the 'fertility' component. This is similar to previous results presented by [START_REF] Occhipinti | Multicommodity mineral systems analysis highlighting mineral prospectivity in the Halls Creek Orogen[END_REF]; (c) Prospectivity map produced without the 'source' component. This result is comparable with the model presented in Fig. 13a, suggesting the source layer cannot make significant differences in gold prospectivity.

Figure Captions

Appendices

Appendix 1. Compilation of Sm-Nd data across the Halls Creek Orogen (includes: this study, [START_REF] Sheppard | High-and low-K granites and adakites at a Palaeoproterozoic plate boundary in northwestern Australia[END_REF][START_REF] Griffin | Tectonic implications of Palaeoproterozoic post-collisional, high-K felsic igneous rocks from the Kimberley region of northwestern Australia[END_REF]Sun and Hoatson, 2000, unpublished

  ), as they used felsic and intermediate rock to investigate Australia's lithospheric architecture on a large scale, whereas we are going to track the juvenile (i.e. mantle-derived) rocks and their relations to gold and nickel mineral system in the Halls Creek Orogen. The locations of samples overlain with the geological map are shown in Appendix 2.Nine samples of felsic and mafic intrusions across the Central Zone of the Halls Creek Orogen are analysed for this study. Sm-Nd isotopic values were determined on crushed whole-rock samples by isotope dilution. All analyses were carried out at the Géosciences Rennes Laboratory at the University of Rennes 1. Samples were spiked with a 150 Nd-149 Sm mixed solution and dissolved in HF-HNO 3 . REE elements were separated using BioRad AG 50W × 8 H + 200-400 mesh cationic resin. Sm and Nd were separated and collected by passing the solution through a further set of ion exchange columns loaded with Ln spec Eichrom resin. Sm and Nd were loaded with HNO3 reagent on to double Re filaments and analysed in a Finnigan MAT262 multi-collector mass spectrometer in static mode. In each analytical session, the unknowns were analysed together with the Ames nNd-1Nd standard, which during the course of this study yielded an average of 0.511956 (standard deviation = 4.95 × 10 -6 ). All analyses of the unknowns are adjusted to a nominal 143 Nd/ 144 Nd value of 0.511850 for the La Jolla standard. Mass fractionation was monitored and corrected using the value 146 Nd/ 144 Nd = 0.7219. Procedural blanks analysed during the period of these analyses were ∼100 pg and are considered to be negligible compared to the total quantity of Nd in the samples. The calculated epsilon Nd (ɛNd), and two-stage model age (T 2 DM ) values were used to generate isotopic maps across the Halls Creek Orogen by applying two approaches. The first involved gridding ɛNd and T 2 DM map generated in ArcMap by undertaking inverse distance weighted (IDW)

  The pre-1900 Ma magmatic rocks of the Eastern Zone include Sophie Downs Granites and Ding Dong Downs Volcanics have εNd ranging from -4.64 to 0.15 and T 2 DM ranging from 2.8 to 2.4 Ga, recording the melting of the pre-existing Neoarchean basement. The εNd of metavolcanic rocks of the Brim Rockhole and Biscay formations range from -0.78 to 4.77 and younger T 2 DM between 2.4 and 2 Ga suggesting more mantle inputs in their isotopic signature. The metasediments of the 1870-1840 Ma Olympio Formation and including trachytic rocks of the c. 1857 Ma Maude Headley Member have negative εNd ranging from -1.60 to -4.23 and T 2 DM ranges from 2.7 to 2.5 Ga, recording the reworking and melting of the Neoarchean basement. The positive εNd value and T 2 DM ranging from 2.3 to 2.1 (Ga) of the c.1835 Ma Woodward Dolerite suggesting a juvenile mantle-derived magma input.

  summary, the Nd depleted mantle model ages across the Halls Creek Orogen suggest that major terrane boundaries separate Neoarchean basement from more juvenile Paleoproterozoic rocks of the Central Zone (Fig. 4c). The 2.6-2.3 Ga T 2 DM model ages of the Sally Downs Supersuite, which formed during a collisional event, show the presence of Neoarchean basement during the Halls Creek Orogeny when suturing of the North Australian and Kimberley cratons occurred. There is a generally well-correlated distribution of model ages with the known geology of the Halls Creek Orogen. The majority of Archean model ages (T 2 DM ) are sampled from the Eastern and Western zones, and emplacement of younger model ages (T 2 DM ) rocks in the Central Zone. The spatial pattern of ɛNd values (Figs. 4d and 5b) through the Halls Creek Orogen highlights the most juvenile signature (positive values) in the Central Zone. These juvenile units are created by upwelling of decompression mantle melt during the back-arc basin development at the margin of Kimberley Craton (Kohanpour et al., 2017). In addition, mafic and felsic igneous rocks of the Sally Down Supersuite represent evolved signature suggesting may be derived from a combination of the melting of a crustal source region (i.e. Neoarchean basement), as well as juvenile mantle magma inputs. The igneous rocks of Biscay and Brim Rockhole formations, and Woodward Dolerite in the Eastern Zone also show juvenile values.

  Evidence of deep connectivity to mantle-sourced melts is interpreted form the geological features associated with both nickel and gold mineralization. These features are deep and crustal-scale structures representing fluid pathways, and juvenile rocks representing mantle-sourced melts. The age of gold mineralisation (1838-1826 Ma, during the early stages of the 1835-1805 Ma Halls Creek Orogeny) and intrusion of prospective nickel sulfide-bearing mafic-ultramafic rocks before c.1835 Ma illustrate that nickel and gold mineralisation are correlated with the marginal basin development and subsequent basin closure.A transition from basin development to closure resulted in nickel to gold producing system in the Halls Creek Orogen. Basin development and upwelling of mantle-derived melts, development and reactivation of deep crustal faults and exhumation of the crust(Lindsay et al., 2016b) are the critical processes common to the formation, preservation, and spatial distribution of both nickel and gold deposits across the Halls Creek Orogen.

Fig. 1 .

 1 Fig.1. Simplified map of major lithological units, and structures of the Lamboo Province; sites of known gold deposits and nickel occurrences from MINEDEX plotted on the map.

Fig. 2 .

 2 Fig.2. Three main geodynamic processes in the Halls Creek orogen[START_REF] Kohanpour | Examining tectonic scenarios using geodynamic numerical modelling: Halls Creek Orogen[END_REF]. (a) Oceanic crust subduction, slab pull, and extensional regime led to basin development and upwelling of decompression melt; (b) Switch from extension to compression result in basin

Fig. 4

 4 Fig. 4. T 2 DM and εNd maps of the Halls Creek Orogen, (a-b) generated by inverse distance weighted (IDW) interpolation in ArcMap; (c-d) created by assigning the calculated values to the lithological units. Location of the samples, isotopic data, and the crystallization age of the related lithological units superimposed over the maps (Data are in Appendix 1). Grid colour in areas without samples are purely based on interpolation and cannot show the isotopic signature of the underlying crust. (a and c) The T 2 DM maps present the lithological units in the Central Zone with the crystallization ages of (1865-1835 Ma) show younger model ages, while the samples with Archean model age are mainly located in the Eastern and Western zones. (b and d) The figures present the juvenile magma inputs (positive εNd) in the centre of the Orogen, and in some igneous rocks of the Eastern Zone. The lithological units with crystallisation ages of c.1865-1835 Ma are more juvenile and have younger model age.

Fig. 5 .

 5 Fig. 5. (a) Magmatic age versus model age (T 2 DM ) for samples in the Halls Creek Orogen, suggests reworking of Neoarchean basement in the Eastern and Western zones and younger crustal growth mainly in the Central Zone. (b) Magmatic age versus epsilon Nd (εNd), shows the Western and Eastern zones have more evolved isotopic signature, whereas juvenile mantle input mainly occurred in the Central Zone. Fields show the evolution of Neoarchean basement and Halls Creek rocks through time.

Fig. 6 .

 6 Fig.6. Representative maps of 'source' for magmatic nickel sulfide (a) and orogenic gold (b) mineralization styles resulting from the fuzzy algebraic OR of distance to selected lithological units based on their tectonic settings.

Fig. 7 .

 7 Fig. 7. Representative map of 'lithospheric architecture', resulting from a fuzzy algebraic OR of terrane boundaries and major deep structures with buffer distances of 10 km for terrane boundaries and 5km for major structures.

Fig. 8 .

 8 Fig. 8. Evidence layers used as proxies for 'depositional site': (a) distance to non-major faults; (b) distance to fold axis; (c) kernel density of fault bends; (d) geological complexities calculated as kernel density of faults and lithological units; (e) kernel density of rheological contrast; (f) kernel density of chemical reactivity contrast.

Fig. 9 .

 9 Fig. 9. Representative maps of 'depositional sites' for magmatic nickel sulfide (a), and orogenic gold deposits (b), calculated from fuzzy overlays of evidence layers presented in Fig.8.

Fig. 10 .

 10 Fig. 10. (a) Location of gold and nickel deposits in the Halls Creek Orogen, superimposed over the εNd values of the lithological units. A strong correlation of mineralization to a juvenile signature is observed. (b) Classified map of the spatial pattern of εNd used as a proxy for 'fertility' component.

Fig. 11 .

 11 Fig. 11. (a) Map of the regional metamorphic grade of lithological units of the Halls Creek Orogen (Occhipinti et al., 2016); (b) Representative map of 'preservation' used for the final fuzzy overlay of orogenic gold prospectivity models.

Table Captions Table 1 .

 Captions1 Fuzzy inference network for nickel and gold prospectivity modelling; Halls Creek Orogen.

Table 2 .

 2 40 Ar/ 39 Ar muscovite results from the gold deposits, Halls Creek Orogen.

Table 3 .

 3 New Sm-Nd data for selected Paleoproterozoic units across the Halls Creek Orogen.

Table 4 .

 4 Search area reduction statistics.

Table 5 .

 5 Search area reduction statistics for orogenic gold deposit prospectivity models

  data from GSWA, Geoview website).Appendix 2. Geographical distribution of Sm-Nd samples on the geological map of the Halls Creek Orogen; the numbers present sample "Id" in Appendix 1. Appendix 3. Full data table of 40 Ar/ 39 Ar results.

Table 4 .

 4 Search area reduction statistics

	Mineral

systems Percentage of map in the top 50 th percentile of map (Prospective) Area (km 2 )

	Orogenic gold deposit	3.2	742
	Magmatic nickel	2.2	517
	sulfide
	Mineral systems	Percentage of map in the low 50 th percentile	Area (km 2 )
		of map (Unprospective)
	Orogenic gold deposit	96.8	22325
	Magmatic nickel	97.8	22550
	sulfide

Table 5 .

 5 Search area reduction statistics for orogenic gold deposit prospectivity models

Models Percentage of map in the top 50 th percentile of map (Prospective) Area (km 2 )

	Without preservation (metamorphic map)	4.13	952.7
	component (Fig.14a)
	Without fertility (isotopic map) component	6.86	1582.6
	(Fig.14b)
	Without source component (Fig. 14c)	3.4	781.4
	Models	Percentage of

map in the low 50 th percentile of map (Unprospective) Area (km 2 )

	Without preservation(metamorphic map)	95.87	22114.3
	component (Fig.14a)
	Without fertility (isotopic map) component	93.14	21484.4
	(Fig.14b)
	Without source component (Fig. 14c)	96.6	22285.6

T 2DM (Ga) calculated after the method of [START_REF] Liew | Genesis of granitoid batholiths of Peninsular Malaysia and implications for models of crustal evolution: Evidence from a Nd/Sr isotopic and U/Pb zircon study[END_REF], assuming a 147 Sm/ 144 Nd ratio of average continental crust 0.12.

Age is the considered age for the lithological units based on the GSWA reports; Decay constant of 147 Sm = 6.54 x 10 -12 .

Highlights:

 The link between nickel and gold mineral systems in the Halls Creek Orogen (HCO).

 Mineral systems analysis by integration of geodynamics, geophysics and isotopes.  Strong association between nickel-gold mineralisation and positive εNd value.  Whole-rock Nd confirmed the input of juvenile melts in the centre of the HCO.  40 Ar/ 39 Ar revealed the relation of gold mineralisation and basin closure.