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This study, via combined analysis of geophysical and geochemical data, reveals a lithospheric architecture characterized by crust–mantle decoupling and vertical heat-flow conduits that control orogenic gold mineralization in the Ailaoshan gold belt on the southeastern margin of Tibet. The mantle seismic tomography indicates that the crust–mantle decoupled deformation, defined from previous seismic anisotropy analysis, was formed by upwelling and lateral flow of the asthenosphere, driven by deep subduction of the Indian continent. Our magnetotelluric and seismic images show both a vertical conductor across the Moho and high Vp/Vs anomalies both in the uppermost mantle and lowest crust, suggesting that crust–mantle decoupling promotes ponding of mantle-derived basic melts at the base of the crust via a heat-flow conduit. Noble gas isotope and halogen ratios of gold-related ore minerals indicate a mantle source of ore fluid. A rapid decrease in Cl/F ratios of lamprophyres under conditions of 1.2 GPa and 1050°C suggests that the ore fluid was derived from degassing of the basic melts. Similar lithospheric architecture is recognized in other orogenic gold provinces, implying analogous formational controls. [ABSTRACT FROM AUTHOR]

Timing of the major Baiyun gold deposit (~ 70 t Au) in the northeastern North China Craton is controversial. A textural and geochronological study of high-grade gold ores identifies three generations of xenotime (Xtm-1, Xtm-2 and Xtm-3), even in single grains. The oldest Xtm-1, in grain cores, is of metamorphic origin, with very high U and U/Th ratios, and hump-shaped, HREE-enriched patterns with maximum normalized values at Yb and large negative Eu anomalies. It is dated at 1856 ± 6 Ma, consistent with its crystallization during regional metamorphism related to cratonization. In contrast, 244 ± 2 Ma Xtm-2 overgrowths are of hydrothermal origin, having low U and U/Th ratios and hump-shaped, MREE-enriched patterns with maximum normalized values at Ho and negligible Eu anomalies. Xtm-2 records a previously unrecognized Middle Triassic hydrothermal episode. Xtm-3, in equilibrium with native gold-hosting pyrite and rutile, is also hydrothermal. The Xtm-3 domains have similar U, U/Th ratios, and MREE-enriched patterns to Xtm-2, but a younger crystallization age of 231 ± 1 Ma. Associated rutile grains that show close textural associations with auriferous pyrite and native gold have an in situ SIMS U–Pb an intercept age of 229 ± 4 Ma, consistent with that of Xtm-3. Collectively, these reliable ages indicate that gold mineralization at Baiyun occurred at ca. 230 Ma, predating the emplacement of granite intrusions by more than 3 million years. Both the Middle Triassic hydrothermal event (~244 Ma) and the Late Triassic gold mineralization event (~230 Ma) lie within the temporal window of collisional tectonics in the host orogen. In combination, the new geochronology and fluid-inclusion and geological data support Bayun's classification as an orogenic gold deposit. [ABSTRACT FROM AUTHOR]

The United States Geological Survey (USGS) Three-part Undiscovered Mineral Resource Assessment provides a framework for estimating undiscovered mineral endowment. Previous studies that applied the Three-part Assessment to estimate the undiscovered orogenic gold endowment of the Sandstone Greenstone Belt, Western Australia, have relied upon dated or expert-derived grade-tonnage models. Here, several assessments are conducted using local grade-tonnage models, comprising known orogenic gold deposits within the entire Yilgarn Block and several individual terranes with contrasting lithosphere- to terrane-scale characteristics. These models are generated through comprehensive review of historical exploration, resource and production data. Based on these models, the Sandstone Greenstone Belt is estimated to contain significant undiscovered gold mineralisation, with a median total endowment of between 166 and 298 t gold, and mean of 167–319 t gold. Although these updated grade-tonnage models provide an approximately 80 per cent variation in predicted gold endowment, it is still evident that the belt remains an under-explored region within the Yilgarn Block, Western Australia. [ABSTRACT FROM AUTHOR]

The orogenic gold deposits along the NNW-trending Ailaoshan shear zone are formed during Miocene continental collision, after a complex history of Neoproterozoic subduction, Late Triassic amalgamation between the Indochina and South China blocks after closure of the Paleo-Tethyan Ocean, and Oligocene-Eocene continental-scale shearing related to the Indian-Eurasian continental collision. As a result, the eastern Neoproterozoic basement with ductile shear zones was thrust over the western metasedimentary rocks and Paleo-Tethyan ophiolites affected by brittle faulting. These tectonically juxtaposed successions were underlain by lithosphere metasomatized in the Neoproterozoic. The gold-hosting western succession is characterized by tightly folded Silurian to Permian metasedimentary rocks, overlain by gently folded Late Triassic metasedimentary rocks, and cut by secondary NW-trending shear zones. This crustal architecture controlled migration of ore fluid towards the cessation of regional ductile deformation at ca. 22 Ma, with major ductile shear zones serving as the main conduit, tight folds, and jogs or intersections on subsidiary brittle shear zones as the fluid trap, and Late Triassic rocks as the seal. Gold-rich rims on disseminated gold-poor sedimentary pyrite with a limited δ34S range from − 3 to 3‰, pyrite He-Ar isotope ratios, and the timing of mineralization within retrograde metamorphism suggest an important metal contribution from mantle lithosphere. The auriferous fluid, derived from previously metasomatized mantle lithosphere, is interpreted to have advected up the Ailaoshan shear zone into the metasedimentary sequence during mantle upwelling, clearly contrasting with widely accepted crustal metamorphic models for Phanerozoic orogenic gold deposits. [ABSTRACT FROM AUTHOR]

Global gold deposit classes are enigmatic in relation to first-order tectonic scale, leading to controversial genetic models and exploration strategies. Traditionally, hydrothermal gold deposits that formed through transport and deposition from auriferous ore fluids are grouped into specific deposit types such as porphyry, skarn, high- and low-sulfidation–type epithermal, gold-rich volcanogenic massive sulfide (VMS), Carlintype, orogenic, and iron-oxide copper-gold (IOCG), and intrusion-related gold deposits (IRGDs). District-scale mineral system approaches propose interrelated groups such as porphyry Cu-Au, skarn Cu-Au-Ag, and highsulfidation Au-Ag. In this study, the temporal evolution of subduction-related processes in convergent margins was evaluated to propose a continuum of genetic models that unify the various types of gold deposits. At the tectonic scale of mineral systems, all hydrothermal gold deposits are interrelated in that they formed progressively during the evolution of direct or indirect subduction-related processes along convergent margins. Porphyryrelated systems formed initially from magmatic- hydrothermal fluids related to melting of fertile mantle to initiate calc-alkaline to high-K felsic magmatism in volcanic arcs directly related to subduction. Formation of gold-rich VMS systems was related to hydrothermal circulation driven by magmatic activity during rifting of oceanic arcs. Orogenic gold deposits formed largely through fluids derived from devolatilization of the downgoing slab and overlying sediment wedge during late transpression in the orogenic cycle. Carlin-type deposits, IRGDs, and some continental- arc porphyry systems formed during the early stages of orogenic collapse via fluids directly or indirectly related to hybrid magmatism from melting of lithosphere that was metasomatized and gold-fertilized by earlier fluid release from subduction zones near margins of continental blocks. The IOCGs were formed during postorogenic asthenosphere upwelling beneath such subductionrelated metasomatized and fertilized lithospheric blocks via fluid release and explosive emplacement of volatile-rich melts. Thus, importantly, subduction is clearly recognized as the key unifying dynamic factor in gold metallogenesis, with subduction-related fluids or melts providing the critical ore components for a wide variety of gold-rich deposit types. [ABSTRACT FROM AUTHOR]

The 13-km-long Sanshandao gold belt along the NNE-trending Sanshandao Fault has highly variable orogenic gold endowment along-strike. New thermochronological data from the small Cangshang gold deposit demonstrate similar degrees of uplift and exhumation rates as for larger deposits, negating selective preservation as the prime gold-endowment factor. The Haiyu, Sanshandao, Xiling, and Cangshang deposits, of variable gold endowment, lie adjacent to NE-ENE-trending jogs, similar to those at Jiaojia and Linglong, so these structures cannot be the prime control on gold mineralization. Ore-zones show a broad gentle northeast plunge, with the southwestern Cangshang and Xinli deposits being closest to the ground surface, and the northeastern Haiyu deposit being the deepest. Thus, preferential erosion of the shallower southwestern orebodies could be a factor affecting endowment. Another variable is the depth of drilling. At Haiyu-Sanshandao, gold mineralization is better developed on more gently dipping fault segments, consistent with a thrust component of oblique slip along them. Relative to the northeastern deposits, the Cangshang and Xinli deposits are located in areas where relatively shallow drilling has intersected ore zones on steeply dipping fault segments, indicating the potential for deeper drilling to intersect gold ore along deeper more gently dipping segments. Heterogeneous gold endowment is thus largely a formational factor related to the plunge of orebodies combined with the variable depth of drilling along the Sanshandao Fault. Over the entire Jiaodong gold province, there are equivalent-age mesozonal to epizonal orebodies, implicating their preservation at different crustal levels and thus increasing the province-scale gold endowment potential and probability of further exploration discoveries. [ABSTRACT FROM AUTHOR]

Most, if not all, orogenic gold deposits form during the late stages of deformation. In some cases, there is barren pre-mineralization hydrothermal alteration which may be part of a single progressive hydrothermal event or a temporally distinct event relative to deposition of gold. At the Huangjindong orogenic gold deposit in the Jiangnan Orogen of southern China, there are two phases of vein generation, the earlier of which is largely barren. Structural analysis, petrography, mineralogy, and in situ laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) gold mapping of different generations of gold-bearing sulfides reveal the relationship between different phases of hydrothermal alteration and quartz veins. Pre-existing barren and brittle quartz veins, which are controlled by tight folds and thrust faults, provide favorable competent hosts for later overprinting by gold-bearing ore-bearing fluids that infiltrated during ongoing reverse-sinistral fault movement. These overpressured fluids caused hydrofracturing to complete brecciation of segments of the earlier quartz veins and associated pre-existing breccias, with deposition of auriferous quartz-sulfide veins and breccia cements or matrices within them. Although fluid inclusion data are non-definitive, fluid pressure fluctuations are interpreted to have resulted in phase separation within the ore fluid which was primarily responsible for destabilization of gold complexes and deposition of native gold with other invisible gold-bearing ore-related sulfides formed by sulfidation reactions, in hydrofractures and breccia matrices. Thus, competent barren quartz veins in fold/thrust belts may locally host superimposed gold mineralization and provide favorable targets for gold resources. [ABSTRACT FROM AUTHOR]

The genesis of hypozonal orogenic gold deposits is highly controversial, with both crustal metamorphic fluids and variously derived sub-crustal fluids suggested as fluid and metal sources. The Lower Jurassic Danba gold deposit, a rare Phanerozoic hypozonal orogenic gold deposit on the western margin of the Yangtze Craton, China, provides an opportunity to resolve these controversies. Danba is characterized by biotite–amphibole alteration and pyrrhotite-dominant ore assemblages formed at ~ 500–600 °C. The δ34S values of ore-related pyrrhotite range from + 3.1 to + 9.9‰, in sharp contrast to those of syn-sedimentary pyrrhotite from Devonian host rocks which are between − 6.8 and − 9.5‰. The Pb isotope compositions of ore-related pyrrhotite, with 206Pb/204Pb = 17.85–18.25 and 207Pb/204Pb = 15.48–15.67, are less radiogenic and more variable than those of unaltered host rocks. These differences, combined with the hypozonal feature of the deposit, indicate that ore metals and sulfur were derived from a sub-crustal, rather than a local crustal source. The PGE patterns of ore-related pyrrhotites are similar to those of sulfides in Baltic mantle lithosphere that was metasomatized by aqueous fluids in terms of marked enrichment of Pd and Ru but significantly differ from those of magmatic intrusions and related magmatic–hydrothermal deposits. This suggests that the metals that formed the Danba deposit were transported via aqueous fluid from metasomatized mantle lithosphere rather than from a magmatic source. The δ18O of mantle fluid calculated from hydrothermal quartz and biotite ranges from 10 to 12‰. The anomalously high S and O isotope ratios and variable Pb isotope ratios, together with PGE data, support a model in which the inferred mantle lithosphere source was significantly hydrated, metasomatized, and fertilized by fluid derived from subducted oceanic sediments with elevated δ34S and δ18O values. Geological evidence suggests that this subduction event was Neoproterozoic in age. This study defines a model in which hydrated and metasomatized mantle lithosphere was formed during early subduction, but it was over 500 million years later, during later Lower Jurassic asthenosphere upwelling, that metal- and sulfur-rich fluid was released into the crust to form the Danba gold deposit. [ABSTRACT FROM AUTHOR]

The term orogenic gold deposits has been widely accepted, but there has been continuing debate on their genesis. Early syn-sedimentary or syn-volcanic models and hydrothermal meteoric-fluid models are now invalid. Magmatic-hydrothermal models fail because of the lack of consistent spatially associated granitic intrusions and inconsistent temporal relationships. The most plausible models involve metamorphic fluids, but the source of these fluids is equivocal. Intra-basin sources within deeper segments of the hosting supracrustal successions, the underlying continental crust, subducted oceanic lithosphere with its overlying sediment wedge, and metasomatized lithosphere are all potential sources. Several features of Precambrian orogenic gold deposits are inconsistent with derivation from a continental metamorphic-fluid source. These include the presence of hypozonal deposits in amphibolite-facies domains, their anomalous multiple sulfur isotopic compositions, and problems of derivation of gold-related elements from devolatilization of dominant basalts in the sequences. The Phanerozoic deposits are largely described as hosted in greenschist-facies domains, consistent with supracrustal devolatilization models. A notable exception is the Jiaodong gold deposits of China, where ca. 120-Ma gold deposits are hosted in Precambrian crust that was metamorphosed over 2000 million years prior to gold mineralization. Other deposits in China are comparable to those in the Massif Central and elsewhere in France, in that they are hosted in amphibolite-facies domains or clearly post-date regional metamorphic events imposed on hosting supracrustal sequences. If all orogenic gold deposits have a common genesis, the only realistic source of fluid and gold is from devolatilization of a subducted oceanic slab with its overlying gold-bearing sulfide-rich sedimentary package, or the associated metasomatized mantle wedge, with CO2 released during decarbonation and S- and ore-related elements released from transformation of pyrite to pyrrhotite at about 500 °C. Although this model satisfies all geological, geochronological, isotopic, and geochemical constraints, and is consistent with limited computer-based modeling of fluid release from subduction zones, the precise mechanisms of fluid flux are model-driven and remain uncertain. From an exploration viewpoint, the model re-emphasizes the ubiquitous occurrence of orogenic gold deposits in subduction-related orogenic belts and importance of continental-scale lithosphere-tapping fault and shear zones to focus large volumes of auriferous fluid. It confirms the importance of the consistent spacing between world-class deposits, broadly equivalent to the depth of the Moho, as derived from empirical observations. [ABSTRACT FROM AUTHOR]

The 920 km2 Archean Sandstone greenstone belt lies in the central-northern part of the Southern Cross Domain of the Youanmi Terrane, Western Australia. The belt, forming an arrow-head geometry, is bounded by the Youanmi and Edale shear zones on its eastern and western margins, respectively. The belt has a total gold endowment, including historic production, resources and reserves, of approximately 62 t (2.0 Moz). Most known deposits are situated within a central-southern ultramafic domain, although this is likely a function of exploration focus. The distribution of historical exploration efforts and domaining of deposit types, based on litho-structural controls on ore formation, highlight the potential for significant undiscovered deposits, hosted within arrays of shear zones parallel and adjacent to the lithosphere-scale Youanmi and Edale shear zones. [ABSTRACT FROM AUTHOR]

The Danba gold deposit is located in a poorly-documented gold province on the north-western margin of the Yangtze Craton. It is sited in Devonian sequences in a high-grade metamorphic terrane that includes an extensional metamorphic core complex. Around the deposit, peak metamorphic conditions of 6 ± 0.5 kbar and 650 ± 50 °C at ca. 193 Ma were followed by retrograde sillimanite-grade conditions of 4.5 ± 0.5 kbar and 550 ± 50 °C. The deposit is hosted in a broadly strata-bound ductile-brittle shear zone with high-T proximal alteration assemblages of biotite-amphibole-plagioclase and ore assemblages dominated by pyrrhotite, but with a strong association between gold and bismuth tellurides. Alteration mineral thermobarometers, together with heating/freezing studies of low-salinity H2O-CO2-CH4 fluid inclusions, indicate P-T conditions of early ore deposition of approximately 4-5 kbar and 500-650 °C at around 185 ± 9 Ma indicated by Re-Os geochronology on ore-related molybdenite. In conjunction, all data demonstrate that Danba represents a Lower Jurassic hypozonal orogenic gold deposit that formed during post-peak metamorphic retrogression. The primary high P-T nature of the deposit, combined with its late-metamorphic timing, negate that the ore fluid was sourced via devolatilization of the hosting supracrustal sequences. A deep externally-derived ore-fluid source is required. The most likely source is the K-H2O-CO2 and ore-metal fertilized lithospheric mantle that was metasomatized during Neoproterozoic subduction. It is proposed that transition from lithospheric transpression to extension in the Jurassic triggered the devolatilization of this metasomatized lithosphere to cause the formation of this rare Phanerozoic amphibolite-hosted gold deposit at Danba. [ABSTRACT FROM AUTHOR]

The Xincheng gold deposit, hosted by the Early Cretaceous 132 to 123 Ma Guojialing-type granitoids in northwest Jiaodong Peninsula, southeast North China craton, formed about 2 billion years later than regional metamorphism of the Archean Jiaodong basement rocks. The Xincheng deposit comprises mineralized zones with three types of hydrothermal pyrite associated with gold, tellurides, and a variety of sulfides: py1 as disseminated euhedral to subhedral grains in altered granitoids around quartz veins; py2 as subhedral grains with brittle eataclastic textures and fractures in quartz-pyrite veins; and py3 as subhedral, partially corroded crystals in sulfide-rich veins or veinlets. All three generations of pyrite are unzoned and have low trace element contents, including very low lattice-bound gold contents: (py1: 0.180 ppm; py2: 0.053 ppm; py;: 0.060 ppm). Given that there is 10 to 15% pyrite in the ore zone at Xincheng, its very low gold content indicates that it contributes <0.2% of gold to the 7.75 g/t gold in the orebody. Instead, over 99% of the gold is present as discrete electrum and/or gold (total range 0.02-59% silver) grains, which are largely sited in fractures at all scales in pyrite, other ore minerals, and quartz. Importantly, visible gold in py.3 is also sited on solution-corroded pyrite grains. The pyrite textural and geochemical data indicate that it is impossible to derive the high gold-grade orebodies through local remobilization of originally lattice-bound gold in pyrite. Instead, the gold is interpreted to have been deposited through sulfidation reactions and phase separation of a H2O-CO2 ore fluid during progressive brittle eataclastic deformation associated with seismic activity and regional sinistral transtensional shear movement. This concomitant fluid infiltration and deformation caused episodic deposition and fracturing and corrosion of earlier formed pyrite and deposited visible gold in dilational cracks. The coupled development of the transtensional, rather than normal transpressional setting, and precipitation of gold within dilational veins and wall-rock alteration facilitated the deposition of visible gold and an exceptionally high gold tenor. All deposit characteristics indicate that the Xincheng gold deposit is a member of the epizonal orogenic deposit class. [ABSTRACT FROM AUTHOR]

In terms of metallogenic models at the global scale, Groves et al. summarize evidence for a sub-crustal ore-fluid source and propose that the genesis of orogenic gold deposits is either directly or indirectly related to subduction in convergent-margin geodynamic settings. Feng et al. use zircon and monazite ages combined with stable isotope data to determine that gold mineralization at the Daliahang deposit (Jiaodong Gold Province, eastern China) occurred significantly after the igneous events, and they also argue for a deep-sourced mineralizing fluid. The Guest Editors have every confidence that this Thematic Issue will be a landmark publication, both in terms of development of holistic models for orogenic gold deposits and their exploration significance and in terms of deposit-scale controls on ore shoots that aid brownfield exploration, the current mainstay of the gold mining industry. [Extracted from the article]

Whether orogenic gold deposits formed from crustal or subcrustal sources is debated, and their link to orogenic processes is ambiguous. Gold mineralization in the Triassic East Kunlun-West Qinling Orogen, China, displays a spatial zonation in terms of its ages and stable isotope compositions. In the West Qinling segment, most gold deposits formed in a back-arc setting at 220~210 Ma during a collisional episode within late slab rollback. These deposits have dominant δ34S of 5-15‰ and δ18Ofluid of 10-14‰, whereas those formed in the suture zone at 210-170 Ma, during a post-collisional episode after slab break-off, have lower d34S of -5-+5‰ and d18Ofluid of 6-10‰. In the East Kunlun segment, those deposits that formed in a continental-arc setting and its related suture zone at 240-200 Ma, in collisional to post-collisional episodes associated with slab break-off, have δ34S and δ18Ofluid values that are essentially similar to those in the West Qinling suture. d34S values of ore sulfide separates and rims of zoned pyrites that have mantle-like signatures, in contrast with crustal signatures of host rocks, are indicative of subcrustal ore-fluid sources. The combined chronological and stable isotope shifts are consistent with a model in which ore fluids for gold mineralization in a back-arc setting were sourced from mantle lithosphere that was metasomatized by subducted oceanic sediment; whereas those in a continental-arc setting--including its suture zone--were sourced from fluid derived from altered oceanic crust. This study thus provides new insights into the complexity of orogenic gold systems in evolving orogens. [ABSTRACT FROM AUTHOR]

Six orogenic gold deposits constitute the Yangshan gold belt in the West Qinling Orogen. Gold is mostly invisible in solid solution or in the sulfide lattice, with minor visible gold associated with stibnite and in quartz-calcite veins. Detailed textural and trace-element analysis of sulfides in terms of a newly-erected paragenetic sequence for these deposits, together with previously published data, demonstrate that early magmatic-hydrothermal pyrite in granitic dike host-rocks has much higher Au contents than diagenetic pyrite in metasedimentary host rocks, but lower contents of As, Au, and Cu than ore-stage pyrite. Combined with sulfur isotope data, replacement textures in the gold ores indicate that the auriferous ore-fluids post-dated the granitic dikes and were not magmatic-hydrothermal in origin. There is a strong correlation between the relative activities of S and As and their total abundances in the ore fluid and the siting of gold in the Yangshan gold ores. Mass balance calculations indicate that there is no necessity to invoke remobilization processes to explain the occurrence of gold in the ores. The only exception is the Py1-2 replacement of Py1m, where fluid-mediated coupled dissolution-reprecipitation reactions may have occurred to exchange Au between the two pyrite phases. [ABSTRACT FROM AUTHOR]

• At Zhenyuan, abundant lamprophyres shared a deep source but were not the ore-fluid source. • Ore fluids incorporated crustal components during advection to deposit site. • Host rocks strongly influenced alteration and mineralization styles, with lamprophyres preferred hosts. The Zhenyuan orogenic gold deposit (>100 t Au), located in the northern part of the Ailaoshan shear zone (ASSZ) in South China, is characterized by extensive alteration and mineralization in a variety of host rocks. In the deposit, abundant Eocene lamprophyres have been infiltrated by ore fluids to produce carbonate veins with zones of disseminated fine-grained gold-bearing pyrite and arsenopyrite on both margins of the veins. Primary phlogopite, K-feldspar and magnetite have been altered to carbonate, sericite and fuchsite. Carbonate minerals and sericite in altered lamprophyre have higher Mg contents than in other host rocks, reflecting the primitive geochemistry of the lamprophyres. Since carbonatization is the primary alteration type in the lamprophyres, whose main primary components are low-Ca phlogopite and K-feldspar, the CaO content of the lamprophyres reflects their degree of alteration. As alteration increases, incompatible element ratios remain essentially constant whereas Sr is enriched with Ca. In addition, Au with Co, Ni, As, Ag, Sb, and Bi are enriched, reflecting the addition of these metal elements during alteration of the lamprophyres. Altered lamprophyres have slightly lower 143Nd/144Nd (t) (0.51240–0.51253) and substantially higher 87Sr/86Sr (t) (0.70716–0.71234) than unaltered or weakly-altered lamprophyres, indicative of crustal contamination. The auriferous ore-forming fluids are thus interpreted to have migrated upwards and interacted with the sedimentary host rocks before altering the lamprophyres. Lamprophyres commonly show a close spatial and commonly temporal association with orogenic gold deposits worldwide. At Zhenyuan, the lamprophyres shared a common deep source to the auriferous ore fluids but did not themselves contribute to this fluid or its gold content. [ABSTRACT FROM AUTHOR]

The Huangjindong gold deposit, with gold resources of ∼80 t, is hosted in Neoproterozoic slates along the Chang-Ping Fault in the Jiangnan Orogen, southern China. The orebodies are dominated by auriferous arsenopyrite-pyrite-quartz-(scheelite) veins; quartz-rich breccias that are cemented by late arsenopyrite, pyrite, muscovite, and quartz; auriferous stibnite-quartz veins; and disseminated gold in arsenopyrite-pyrite-sericite-quartz altered rocks. Neither significant alteration zoning nor ore-element zoning are recognized within the orebodies, although the orebodies at shallower crustal levels are slightly more stibnite-rich. At the regional scale, the first-order control on the distribution of gold deposits is the NNE- to NE-trending crustal-scale, sinistral strike-slip Chang-Ping Fault. As in other gold provinces globally, this controlling fault is not gold mineralized. The gold occurrs in WNW to E-W-trending zones of thrusts and fracture arrays associated with tight ‘locked-up’ asymmetrical folds. The broadly E-W-trending orebodies formed independently within approximately NE-trending fault-bounded corridors defined by the first-order Chang-Ping, and second-order Ni-Wan and Keng-Shang/Chang-Long Faults. Hydrothermal activity was initiated at the ductile-brittle transition, but evolved to brittle-dominated deformation, all within a transpressional environment. Oxygen and hydrogen isotope compositions of fluids (δD = −44.4‰ to −34.2‰; δ 18 O = +8.6‰ to +9.5‰) calculated from gold-related hydrothermal quartz and hydrothermal sericite, respectively, are consistent with a metamorphic source. Sulfur isotope compositions of the gold-bearing arsenopyrite and pyrite (median values between −8.0‰ and −6.0‰) are generally distinct from δ 34 S of the regional Neoproterozoic slates in the Jiangnan Orogen, but overlap the compositions of pyrites in global sediment-hosted orogenic gold deposits. Lead isotope compositions of the gold-bearing arsenopyrite and pyrite ( 206 Pb/ 204 Pb: 17.049 to 18.417; 207 Pb/ 204 Pb: 15.263 to 15.712; 208 Pb/ 204 Pb: 37.597 to 39.220) suggest that the lead was sourced from metamorphic rocks involved in the orogenic events. Therefore, both the stable and radiogenic isotopic data indicate that ore-forming fluids and metals were derived from a metamorphic source, although the precise nature of that source is unclear. On the basis of these geological and isotopic data, Huangjindong is interpreted as an orogenic gold deposit. The gold ore bodies show classic structural controls, being adjacent at the province scale to the crustal-scale Chang-Ping Fault but located in thrusts and associated tight anticlinal fold hinges that lie in corridors between markedly oblique, relatively brittle fault arrays that parallel the Chang-Ping Fault. [ABSTRACT FROM AUTHOR]

The diverse types of Mesozoic intracontinental gold mineralization in the South China Block (SCB) are genetically linked to prolonged oceanic plate subduction. These gold deposits, with estimated resources greater than 2000 tonnes, comprise four gold provinces: Hainan Island, Wuyi-Yunkai Belt, Jiangnan Orogen, and Youjiang Basin. In these provinces, Paleo-Pacific Plate subduction, crustal thickness and composition, structural reactivation, and fluid-wall rock reactions collectively controlled the distribution and diverse features of the Mesozoic intracontinental gold mineralization. Three stages can be identified in the metallogenic evolution of the SCB. (1) Formation of orogenic gold deposits gradually younging from the coast (Hainan) to the hinterland (Youjiang Basin and Jiangnan Orogen) related to flat-slab subduction of the Paleo-Pacific Plate and clockwise rotation of the SCB between 245 and 200 Ma. (2) Formation of intrusion-related Au-(Sb-W) deposits in the western Jiangnan Orogen in a continental extensional setting in the wake of flat-slab subduction between 210 and 195 Ma prior to the early to middle Jurassic hiatus (190–170 Ma) of high-angle subduction and stagnant slab. (3) Between 170 and 90 Ma, intermittent formation of intrusion-related gold deposits in the coastal region (∼160 Ma, ∼100 Ma) and hinterland (∼160 Ma, 140–130 Ma), and the formation of Carlin-type gold deposits in the Youjiang Basin (∼140 Ma) during episodic extension caused by slab foundering and changes in subduction angle. After 90 Ma, regional differential crustal thinning and denudation determined the extent of uplift and exposure of various types of ore deposits. In stage 1, the quartz vein-type and disseminated orogenic gold deposits hosted in Precambrian rocks, and with a subcrustal source, are related to the reactivation of crust-scale NE-trending faults. In contrast, disseminated orogenic gold deposits hosted in Phanerozoic rocks and influenced by fluid-rock reactions relate to landward propagation of a fold-thrust system. In stage 2, intrusion-related Au-(Sb-W) deposits only formed in intracontinental Precambrian rocks and were controlled mainly by shallow, brittle, and extensional NW-trending structures. Highly fractionated late-stage S-type granite (used sensu lato throughout) complexes controlled the distribution of intrusion-related gold-(polymetallic) deposits in stages 2 and 3. In stage 3, stratabound and disseminated Carlin-type gold deposits are restricted to platform facies carbonate sequences, and intrusion-related gold deposits are structurally related to the reactivation of NE-trending faults. Both are interpreted to have a magmatic-hydrothermal source. The crustal architecture of the four gold provinces exhibits marked differences in crustal thickness, contrasts in rheology, abundance of deep faults, and intensity of mantle-crust interaction. Those gold provinces in the central-southeastern SCB are the result of the reactivation of a paleo-orogen, in contrast to those hosted by deformation systems in shallow crust in the western SCB during the Mesozoic. The Carlin-type and intrusion-related gold deposits are located in regions with more mafic and felsic components, respectively, as indicated by seismic Vp/Vs ratios. However, the spatial distribution of orogenic gold deposits is poorly correlated with that of Vp/Vs ratios, suggesting a subcrustal source. • The South China Block exemplified the link between prolonged oceanic subduction with diverse types of gold systems. • Mesozoic gold deposits are widespread over a 1000 km long area from plate boundaries to intraplate settings. • Subduction dynamics, lithosphere architecture, and reworked structures controlled different types of ore formation. • Flat-slab subduction caused progressive orogenic gold formation from coast to hinterland. • Crustal thickness gradient zone, paleo-suture, and transcrustal faults are crucial for future exploration. [ABSTRACT FROM AUTHOR]

[Display omitted] • Both the Early Jurassic and Cenozoic gold mineralization are hosted by NNE-trending faults. • The Daduhe orogenic gold deposits have ore fluids derived from metasomatized mantle lithosphere. • The deposits have similar S-O-He-Ar isotope values to IOCG, Fe-V-Ti and carbonatite REE deposits. The poorly documented Daduhe gold belt on the western margin of the Yangtze Craton, an important metallogenic belt in southwest China, is characterized by typical orogenic gold systems against a highly anomalous geodynamic setting. A synthesis of regional and deposit geology, mineralization ages, and S-O isotopic compositions of 33 gold deposits from the Danba-Kangding-Shimian-Mianning area of the belt reveals regional metallogenic patterns, establishes a consistent genetic model, and demonstrates a source equivalent to other diverse mineral systems on the western margin of the Yangtze Craton. The Daduhe orogenic gold deposits are controlled by the lithosphere-scale Xianshuihe and Anninghe strike-slip faults in the northern and southern segments of the belt, respectively. The alteration and ore mineral assemblages of the Daduhe orogenic gold deposits define a wide range of hypozonal, mesozonal, and epizonal sub-types. They formed during two episodes: 1) Early Jurassic gold mineralization related to closure of the Paleo-Tethys Ocean, with a large hypozonal gold deposit on the margin of the Danba dome in the northern segment; 2) Cenozoic gold mineralization associated with continental collision on the Tibetan Plateau, with small mesozonal and epizonal gold deposits in shear zones in migmatite basement and at contacts with cover sequences in both the northern and southern segments. At the belt and deposit scales, the ore-controlling structures for both mineralization episodes are NNE-trending second-order extensional faults or their intersections with the dominant NW-trending compressional faults. The three deposit sub-types have overlapping δ34S of 0 ∼ 10‰, δ18O fluid of 6 ∼ 11‰, and low He-Ar isotope ratios, all consistent with derivation of ore fluids from metasomatized mantle lithosphere. Importantly, the Daduhe orogenic gold deposits have similar S-O-He-Ar isotope compositions to the giant IOCG, Cu-Ni-PGE, Fe-V-Ti, anomalous porphyry Cu-Mo-Au, and carbonatite-related REE deposits in the Panxi region on the shared margin of the western Yangtze Craton. This suggests that these diverse mineral systems have a common source of ore fluids and metals derived from fertile mantle lithosphere during different geodynamic and metallogenic events. Such a widespread hydrous metal-rich deep source with lithosphere-scale faults as ore fluid pathways, and a depth continuum of orogenic gold deposits in the Daduhe belt suggest a high prospectivity and a higher future gold endowment for the belt. This study adds to an increasing awareness of the diversity of mineral systems on specific craton margins globally. [ABSTRACT FROM AUTHOR]

Geophysical exploration for concealed orogenic gold deposits is challenging because petrophysical contrasts between the gold lodes and their host rocks are normally subtle. Most greenstone-hosted lode‑gold deposits do not contain strong conductors as they normally contain <5 vol% of poorly conductive disseminated arsenopyrite and pyrite. Where there is no outcrop, reliance must be placed on lithological and structural interpretations from aeromagnetic data. Airborne Induced Polarization (AIP) Cole-Cole parameters from helicopter time-domain electromagnetic (HTEM) surveys are demonstrated to be effective in geophysical exploration for concealed gold deposits in the Kabinakagami Lake greenstone belt in Ontario, Canada. Interpretation reveals that most AIP positive responses are associated with clays and all known gold deposits in the study area are in resistive rock formations. Hence, resistivity-scaled chargeability (RSC) can be used to detect weakly chargeable zones within these resistive units. Deep Neural Network (DNN) predictive targeting analysis is utilized to integrate the AIP apparent resistivity, resistivity-scaled chargeability (RSC), EM induction time-constant, and magnetic data. The DNN results imply that the known gold occurrences coincide with high DNN probabilities, and hence exploration targets can be identified based on DNN analysis. From a geological perspective, gold prospects also occur at triple-point junctions between granite intrusions and at probable intersections between potentially hosting shear zones and oblique cross faults or dykes, both common structural geometries for orogenic gold deposits. Consequently, DNN predictive targeting results based both on HTEM and magnetic data, and consistent with expected structural geometries, are proposed as a vectoring tool in the generation of drill targets during exploration for concealed orogenic gold deposits in greenstone belts such as those of the Superior Province, Canada. Deep neural network top 12% target probabilities and the new suggested exploration targets T1 to T4, labelled from southwest to northeast. [Display omitted] • Magnetic, EM and AIP data provide vectors to concealed gold mineralization • Targets at the Kabinakagami greenstone belt are marked by resistive EM anomalies • Template for the interpretation of structural geometry and geophysical datasets [ABSTRACT FROM AUTHOR]

The Daping and Chang'an orogenic gold deposits in the extruded Jinping terrane of the Cenozoic Ailaoshan collisional orogen, on the southeastern margin of the Tibetan Plateau, provide an opportunity to study relationships between the geodynamic evolution of a collisional orogen and orogenic gold mineralization. The Daping gold deposit comprises NW−SE-trending gold lodes hosted by ductile-brittle, dextral-reverse shear zones that developed under sub-horizontal NNE−SSW-oriented compression. In contrast, the Chang'an gold deposit comprises disseminated ores controlled by NW-trending brittle, sinistral strike-slip faults that formed under sub-horizontal NW−SE-oriented compression. Reliable Ar−Ar dating of two gold-related hydrothermal sericites at Daping constrain mineralization to ca. 46−42 Ma, whereas ca. 35 Ma gold-mineralized syenites, the inferred stress field, and published paleomagnetic evidence suggest that the Chang'an deposit formed later at ~23−21 Ma. These different mineralization ages, together with contrasting sulfur isotope compositions of gold-related sulfides at Daping and Chang'an, indicate that the Daping deposit formed in the northwestern part of the Ailaoshan orogen during crustal thickening before extrusion of the Jinping terrane, whereas the Chang'an deposit formed to the southeast at a late stage of terrane extrusion. From this rare window into a gold-mineralized Cenozoic orogen, it can be demonstrated that at least two periods of orogenic gold mineralization occurred at evolving stages of the geodynamic evolution of the collisional orogen. • Multistage orogenic gold events within evolving Cenozoic collisional orogen. • Extruded Jinping terrane hosts tectonically juxtaposed orogenic deposits. • Deep-crust Daping deposit hosted by dextral-reverse shear zones. • Shallow-crust Chang'an deposit hosted by sinistral strike-slip faults. [ABSTRACT FROM AUTHOR]

[Display omitted] • The post-metamorphic and magmatic Jiapigou orogenic gold deposit formed at 152 Ma. • A 3D spherical rotation structural model explains gold orebody distribution. • Deeper potential orebody extensions were targeted, and discovered using the model. The Erdaogou orogenic gold deposit, in the deepest gold mine in China, is situated within a dilational jog in the curvilinear Jiapigou shear zone, which broadly follows the margin of a Neoarchean granite intrusion within Neoarchean high-grade metamorphic basement on the northeastern margin of the North China Craton. Uranium-Pb dating of hydrothermal gold-related monazite provides a robust gold mineralization age of 151.8 ± 6.3 Ma. In contrast, zircon from the ore-hosting metamorphic rock has an age of 2514 ± 18 Ma and that from felsic dykes have ages from 216 to 231 Ma. The mineralization age is much younger than regional metamorphism and magmatism, indicating a subcrustal origin. Within the broad dilational NW-trending jog in the Jiapigou shear zone, various orogenic gold deposits display variable orientations relative to that of the controlling shear zone, implicating district-scale heterogeneous stress. As the strike of the subsidiary ore-controlling Erdaogou shear zone, changes from a N-S trend to a broadly NW-trend, the orebodies exhibit variations in thickness and gold grade. At upper mine levels, the moderately east-dipping Erdaogou shear zone displays reverse-slip movement, implicating a local more-extensional regime, but becomes near-vertical, implicating a more local compressional regime at intermediate depth levels, with a change to steep westerly dips at deeper levels. Based on this structural geometry, a 3D reverse-slip spherical rotation model, involving torsional stresses in a heterogeneous stress regime, is proposed for the ore-controlling Erdaogou shear zone with the vertical segment at intermediate mine levels situated at the maximum rotation point of the torsional motion. Importantly, the average T h and salinity of fluid inclusions in main ore-forming stage quartz from the 1365 m to 1500 m mining levels indicates limited pressure gradients, implicating a deeper continuation of the gold orebody. Based on this structural model, a local more-extensional regime was predicted for the zone where the orientation of the shear zone changes from a vertical to westerly dip. Drilling of this structural target in 2020 successfully located the high-grade new orebodies No. N1 and N2. [ABSTRACT FROM AUTHOR]

(A) AIP relaxation time-constant data superimposed on the RTP data from the Sandy Lake study area (SLGB) and (B) from the Favourable Lake study area (FLGB). • We propose that AIP relaxation time-constant highs be used as vectors in exploration for concealed orogenic gold deposits, especially where they are spatially associated with concealed structural geometries. • Our method is documented at two study areas in the Sandy Lake and Favourable Lake greenstone belts, Superior Province, Canada. • Our study can potentially be used as a template for the integration of structural geometry and multiple geophysical methods combined with follow-up geochemistry for multi-disciplinary exploration of concealed orogenic gold deposits in Archean greenstone belts. Since 2000, gold discovery rates have not reflected the record levels of exploration expenditure, with those discoveries that are made being predominantly in areas of post-mineral cover. Hence, gold exploration has been increasingly focused on concealed exploration targets where geophysics takes on an increasingly important role in the exploration process. Archean orogenic gold deposits are attractive exploration targets that represent a major proportion of global gold resources. Orogenic gold deposits consistently form late during the tectonic and structural evolution of their host terranes, normally during a transition from compressional to transpressional tectonic stress regimes. Thus, for target generation, the late timing of gold mineralization within the structural history of a prospective orogenic belt is crucial, as it means that current geological maps and sections reflect the geometry of the gold deposits at the time of formation unless there has been subsequent orogeny. Lithological contacts between granitic intrusions and volcano-sedimentary greenstone sequences, as well as between volcanic and sedimentary sequences, are important rheological and geochemical trap sites. Lithosphere-scale faults and dilational jogs in second-order faults act as ore-fluid conduits with anticlinal folds as structural traps for ore-fluid infiltration and gold deposition given suitable host rocks and fluid seals. Geophysical exploration for concealed orogenic gold deposits is challenging due to normally subtle petrophysical contrasts between the gold lodes and their host rocks. Most greenstone-hosted lode-gold deposits do not contain strong conductors as they normally contain <5 vol% of disseminated arsenopyrite and pyrite, which are poor conductors, and rarely contain significant quantities of strong conductors such as pyrrhotite. However, pyrrhotite may be a component of rock sequences such as sulfidic shales or cherts adjacent to the orogenic gold lodes. It is proposed that the combination of HTEM and magnetic surveys be used to explore for concealed orogenic gold deposits, using the Favourable Lake and Sandy Lake greenstone belts in the Superior Province, Canada, as a case study. AIP Cole-Cole time-constants, combined with magnetic and EM data, can efficiently detect disseminated pyrite/magnetite at shallow depths, indicating their potential use as vectoring tools for concealed Archean orogenic gold deposits. [ABSTRACT FROM AUTHOR]

The giant Jiaodong gold province, with more than 5000 t of proven gold resources, is unique in that its Mesozoic gold deposits are hosted in a Precambrian basement block. There has long been debate on the source of gold, the mechanism for its extreme enrichment, and a holistic genetic model for these spectacular deposits. In order to improve understanding of these factors, a mineral-system model is proposed for the Jiaodong gold deposits for the first time. It is based on a detailed review of the architecture and composition of the underlying mantle lithosphere, the geodynamic setting at the time of gold mineralization, the geological and geochemical features of the deposits themselves, and mechanisms of their preservation. Regional geodynamic reconstructions, combined with the nature of Mesozoic magmatic systems show that Late Mesozoic breakoff of the subduction slab and rollback of the paleo-Pacific Plate caused asthenosphere upwelling and lithosphere extension and thinning. Robust geochronological studies demonstrate that the Jiaodong gold deposits formed at ca. 120 Ma during a change of subduction direction of the paleo-Pacific Plate and the synchronous transition of tectonic regime from regional compression to transpression or transtension prior to peak extension caused by thinning of the lithosphere. Geophysical exploration data and Hf-Nd isotope mapping of the Jiaodong Peninsula reveal a relatively simple ancient crustal structure cut by near-vertical shear or fault zones, including the lithosphere-scale Tan-Lu and Wulian-Yantai Faults, that provided the first-order architecture for emplacement of mantle magmas and sub-crustal fluids. In terms of fertility, the significant older pre-mineralization crustal metamorphism, combined with sulfur, lead and strontium isotope ratios, indicate a dominant sub-crustal source for the ore components for the Jiaodong gold deposits, consistent with evidence for volatile- and gold-fertilized metasomatized mantle lithosphere beneath the North China Block. Helium-Ar and C-O isotope ratios implicate mantle sources of ore fluids with contamination by crustal components en-route to crustal depositional sites. In terms of crustal architecture, combined geophysical, structural, mineralogical, fluid inclusion, and geochemical studies show that the deeply-sourced ore-fluids and metals advected upwards through lithosphere-scale faults to deposit gold via sulfidation and phase separation in crustal-scale NNE-NE-trending fault systems at mid- to upper-crustal levels. Preservation of disseminated- to stockwork-style deposits and auriferous quartz-pyrite vein deposits was enhanced by deep crustal formation combined with limited uplift and exhumation of the province. The Jiaodong gold deposits, although commonly hosted in granite intrusions, clearly post-date them on the basis of robust and reliable geochronology. The spatial but non-temporal relationships of gold deposits with granites, their strong structural control, and their other characteristics clearly place them in the orogenic gold group. It is suggested, because of their uniqueness, that they be termed 'Jiaodong-type' orogenic gold deposits. [ABSTRACT FROM AUTHOR]

• Jogs in crustal-scale faults with high-angle cross faults control district-scale mineralization. • Heterogeneous stresses and complex fault and dyke arrays around rigid pluton control deposit-scale mineralization. • Contacts between rock units with contrasting rheology control orebody-scale mineralization. • Structurally, gold deposits in the Dashui-Zhongqu District are typical epizonal orogenic gold deposits. Ge'erke (>100 t gold) is one of six Mesozoic gold deposits within the Dashui-Zhongqu District, that collectively have a non-JORC resource of about 150 tonnes gold out of a total of >1100 tonnes gold for the host West Qinling Belt. The deposits in the Dashui-Zhonggu District are deeply weathered to depths of up to 400 m, with secondary Fe-oxides having replaced pyrite and other sulfides. This makes traditional ore deposit studies involving mineralogical, geochemical and isotopic analysis difficult. Thus, their association has been controversial with correlations to deposits that include Carlin and intrusion-related types postulated. However, these associations can be discounted in favour of their classification as epizonal orogenic gold deposits. At Ge'erke, gold mineralization was focused in the hangingwall of a broadly south-dipping southern margin of a granite pluton in a wide variety of fault trends. This complexity was caused by heterogeneous stresses developed around the rigid pluton by the broadly NE-SW directed regional principal maximum stress responsible for the sinistral movement along the crustal-scale faults which control the regional alignment of the West Qinling gold deposits. At the orebody and ore shoot scale, gold mineralization is controlled by rheology contrasts, particularly the fault contacts between crystalline limestone units and granite dykes, which are themselves in a variety of orientations because of inhomogeneous strain around the parent granite pluton. In this region the secondary faults that subparallel the Mianlue Suture and associated crustal-scale faults are poorly gold mineralized in the absence of granite plutons. During exploration, such buried plutons and the orientations of their margins can best be detected by gravity surveys, although magnetic surveys may also be useful. [ABSTRACT FROM AUTHOR]

• Multiple Au, Au-Sb and Sb events related to complex tectonic evolution of Orogen. • Early Devonian intracontinental orogeny and related Au-Sb mineralization. • Triassic distal effect of collisional orogeny and related Au-Sb event. • Early Cretaceous Sb and Au events linked to rollback of paleo-Pacific Plate. • Definition of structural geometries is critical for future exploration targeting. The Jiangnan Orogen, located between the Yangtze and Cathaysia Blocks in southern China, hosts significant gold and antimony resources. Long-standing controversies over the number and precise timing of gold, gold-antimony and antimony mineralization event(s), and the genesis of these deposits, limit the understanding and exploration of this giant gold and antimony system. Together with geological evidence, a critical review of the published geochronological data of these deposits suggest that there were two gold events in the Triassic (~235 Ma) and Early Cretaceous (~142–130 Ma), two gold-antimony events in the Early Devonian (~402 Ma) and Late Triassic-Middle Jurassic (~224–163 Ma: possibly equivalent to the two gold events), and one antimony event in the Early Cretaceous (~130 Ma). There are other possible gold events in the Neoproterozoic or at an even older age, and Ordovician to Early Devonian, which are constrained only by limited geological evidence and a few non-robust isotopic ages. The regional distribution of the gold, gold-antimony and antimony districts, and deposits therein, reveal a first-order control on the mineralization by crustal scale faults which acted as ore-forming fluid pathways connected to deep fluid and metal source areas. Second- and third-order faults that are situated along the jogs of the first-order faults, especially fault corridors defined by NNE-NE-trending second-order faults and third-order NW to E-W-trending discontinuous oblique faults, provided favorable locations for Pre-Cretaceous gold-(antimony) mineralization. In addition, NE-trending open anticlines, linked to deep crustal levels by first-order faults, host significant antimony and minor gold mineralization, and the curvilinear Fanjingshan detachment Fault hosts some gold and antimony deposits. Locally, at deposit to orebody-scales, pre-ore barren quartz veins and magmatic dikes were the loci for mineralization in some gold-antimony deposits. The structural geometry of the pre-Cretaceous gold and gold-antimony deposits suggests an Early Devonian orogenic gold-antimony mineralization event during a transpressional tectonic regime related to coeval intracontinental orogeny between the Yangtze and Cathaysian Blocks. In contrast, Triassic orogenic gold and Triassic-Middle Jurassic orogenic gold-antimony events are interpreted to relate to distal effects of the collision between the North and South China blocks. The structurally-contrasting major Early Cretaceous epizonal antimony mineralization event, together with contemporaneous hydrothermal gold mineralization, is interpreted to have been controlled by normal faults and pre-ore open folds in an extensional tectonic regime related to the distal effects of rollback of the paleo-Pacific Plate after ~135 Ma. For future geoscience-based exploration in the Orogen, documentation and interpretation of critical structural geometries of gold, gold-antimony and antimony deposits is a vital step towards successful target generation. [ABSTRACT FROM AUTHOR]

In situ U–Pb dating of carbonate minerals and Rb–Sr dating of illite was carried out on the Yata sediment-hosted disseminated-type gold deposit in the Youjiang basin, South China. The new study determines the timing of gold mineralization and clarifies the geological conditions required for the successful application of in situ U–Pb dating of alteration-related carbonate minerals. The results suggest that the Yata gold deposit likely formed during two metallogenic episodes. Illite Rb–Sr ages of 178.6 ± 5.8 Ma (MSWD = 1.2) for the 2–0.5 μm fraction and 171.3 ± 3.4 Ma (MSWD = 0.62) for the 0.5–0.2 μm fraction constrain an earlier episode of gold mineralization to >178.6 Ma. Hydrothermal carbonate minerals within the Yata gold deposit are associated with organic matter. In situ U–Pb dating of paragenetically early ankerite and later calcite veins yields ages of 149.0 ± 10.4 Ma (MSWD = 2.0) and 147.3 ± 32.6 Ma (MSWD = 1.8), respectively. These mineral ages and their petrographic relationships provide unequivocal evidence that another episode of gold mineralization occurred in the Early Cretaceous. Importantly, this study demonstrates in situ U–Pb dating is applicable to low-temperature deposits consisting of organic-rich hydrothermal carbonates characteristic of relatively high common Pb. Such deposits potentially include hydrothermal antimony, Carlin-type gold deposits, gold‐uranium, and carbonate-hosted uranium deposits. • Carbonate U–Pb dating constrains the age of late mineralization to ca. 150 Ma. • Illite Rb–Sr ages constrain the early stage of gold mineralization to ca. 178–172 Ma. • U–Pb isotope analysis can provide reliable ages for U-rich hydrothermal carbonates. [ABSTRACT FROM AUTHOR]

Although the term orogenic gold has become widely accepted over the past 20 years for disseminated- to lode-style gold deposits that formed in a variety of tectonic environments within convergent margins, models for orogenic gold systems have remained controversial. The main debates include interpretation of stable isotope and fluid inclusion data that are particularly equivocal for orogenic gold systems, the nature of lithospheric control on the generation of orogenic gold belts, and more critically, the role of deep crustal regional metamorphism or alternatively metasomatized and fertilized mantle lithosphere as sources of ore metals and fluids. The giant to world-class orogenic gold systems of China, now the premier gold producer globally, are in gold provinces or belts of several ages that are mostly marginal to Precambrian cratons or blocks, including the North China Craton and South China Block, an amalgamation of the Yangtze Craton and Cathaysia Block. Deposits from these gold provinces provide crucial evidence to constrain genetic debates. Importantly, following the acceptance that the giant Jiaodong gold province formed over 1700 million years after regional metamorphism in the host terrane, an increasing number of deposits, including the Phanerozoic hypozonal deposit at Danba, are shown to have postdated regional metamorphism and formed from components that were not derived from the host crustal rock sequences. A subcrustal model involving devolatilization of fertilized mantle lithosphere, that was metasomatized via earlier subduction processes involving oceanic sediments and/or altered oceanic crust, is compatible with a variety of data. This includes 40Ar/36Ar vs. 3He/4He mantle-like plots for gold-related pyrite, sulfur isotope compositions of ore-related sulfides that are incompatible with a crustal source, and PGE distribution patterns of spatially related mafic dykes that implicate elevated sulfide contents of underlying mantle lithosphere. Chinese orogenic gold deposits formed in a variety of tectonic regimes from syn -subduction slab rollback, post-subduction slab breakoff, and lithosphere thinning along craton margins, to continent collision. In all cases, lithosphere-scale shear zones and faults were the conduits for ore fluids and metals derived episodically from devolatilization of a subducted slab and/or long-lived metasomatized and fertilized mantle. These fluids deposited gold mineralization in rock sequences adjacent to subsidiary shear zones and faults from crustal depths of >20 km to <5 km, with hydraulic fracturing and fluid phase separation potentially the most important depositional process for lode deposits and fluid-rock reaction dominant in disseminated deposits. As the H 2 O-CO 2 ore fluid containing H 2 S infiltrated into structural-lithological traps, it reacted with the wall rocks under P-T conditions related to depth of gold deposition to produce a continuum of broadly depth-related alteration mineral assemblages. The characteristics of the widespread orogenic gold systems of China strongly implicate a sub-crustal fluid and metal source for orogenic gold in a variety of gold provinces. Based on deposits from outside of China, where gold provinces are more distal to Precambrian cratons, this source is most likely from the devolatilization of down-going subduction zones and sediment wedges in addition to devolatilization of previously fertilized mantle lithosphere as implied by the Chinese examples. • Chinese orogenic gold deposits are pivotal to resolving genetic controversies. • They formed in classic convergent margins but adjacent to craton margins. • There are both accretionary for-arc to back-arc and collisional settings. • Metasomatized mantle lithosphere was the gold, sulfur, and fluid source. • The geodynamic setting of Chinese deposits opens up new exploration search spaces. [ABSTRACT FROM AUTHOR]