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The Arabian-Nubian Shield (ANS) is a rapidly emerging world-class province for gold resources mainly in structurally-controlled quartz ± carbonate veins that are best classified as late Neoproterozoic orogenic gold deposits. Gold has been mined in the Eastern Desert of Egypt, in the northwestern part of the ANS, for >6000 years, that is since the times of the Pharaohs, but production prior to the 1900s was likely only about 25 t and mainly from alluvial workings. In the first half of the 1900s, about 7 t Au was recovered from the El Sid orogenic gold deposit. Today, Sukari is the single major producing mine in the Eastern Desert but many other significant gold occurrences are being actively explored. Formation of the ANS took place during closure of the Mozambique Ocean between the East and West Gondwana continental blocks. Ocean closure led to amalgamation of numerous ca. 870–625 Ma juvenile arc and back-arc igneous and sedimentary rock sequences, with many resulting terrane sutures marked by mafic-ultramafic ophiolitic assemblages and fragments. The 100 m.y. of orogeny beginning at ca. 650 Ma included crustal shortening, lithospheric reworking, escape tectonics, and eventual orogenic collapse. Peak metamorphism was reached in different parts and depths of the orogen diachronously between 620 and 585 Ma, magmatism was widespread during 650–580 Ma, and rapid exhumation of the metamorphosed rocks and mid-crustal intrusions took place from ca. 600 to 580 Ma. Regional fault sets that controlled much of the gold occurrences were related to initial transpression by oblique convergence between the arcs and associated with subsequent sinistral shearing reported as overlapping the exhumation. Because existing geological data are not adequate to fully evaluate the overall terrane history, we have subdivided the Eastern Desert into nine structural blocks, rather than arc terranes, based commonly on bounding shear zones and major faults. The greatest abundance of gold deposits is associated with the NW-trending Najd Fault System that comprises many splays throughout the blocks in the Central Eastern Desert that underwent episodes of shearing at ca. 640–570 Ma. Important deposits are also notably widespread along reactivated east-west thrust faults in the Allaqi-Sol Hamed block of the South Eastern Desert, with significant shearing at 610–580 Ma. Sulfide mineralogy of the Eastern Desert gold-bearing veins is dominated by pyrite, arsenopyrite, and (or) pyrrhotite, in addition to subordinate chalcopyrite, sphalerite, galena and tetrahedrite as well as alteration minerals that include white mica, chlorite, and carbonate, are those typical of orogenic gold deposits. Many gold occurrences are located along sheared margins to granitic intrusions or along contacts between different lithologies; sheared silica- and carbonate-altered ultramafic rocks along many fault zones are particularly widely associated with many of the gold occurrences. Ore-forming fluids were generally low-salinity aqueous-carbonic with most measured δ18O of mineralized quartz ranging from 8‰ to 15‰, δ13C for associated carbonate from −10‰ to −1‰, and δ34S for ore-related sulfides varying between −5 and +10‰, but much more consistent for individual occurrences or deposits. Gold was deposited at temperatures of generally between 250° and 370 °C, depending on location, and largely variable pressures. The few obtained absolute dates on ore formation, from the Fawakhir and Atalla deposits in the Central Eastern Desert, indicate that at least some of the mineralization was formed at ca. 600 Ma. Orogenic gold formed after the cessation of arc-terrane accretion in the ANS and during a period in which most of the shield became established with a 30–40 km-thick continental crust and underwent a transition from compressional/transpressional terrane accretion to post-amalgamation transtensional shearing. This also was marked by a petrogenetic transition from pre- to syn-accretionary, arc-related calc-alkaline I-type magmatism to late- or post-tectonic A-type magmatism within the newly formed shield. Concurrently, the Eastern Desert was affected by widespread crustal flow of aqueous-carbonic fluids, particularly on the through-going, extensive strike-slip shears of the Najd Fault System. Gold and sulfide minerals were deposited in the Eastern Desert shallow and middle crust coevally with rapid terrane exhumation, during changes in fluid chemistry associated with pressure cycling and multiple vein quartz precipitation. Unlabelled Image • Available information on gold occurrences in the Eastern Desert of Egypt is reviewed, assessed and thoroughly discussed. • New ideas of the genesis and controls of the scattered gold occurrences in the shield are herein presented and detailed. • Orogenic gold in the Eastern Desert formed after the cessation of arc-terrane accretion and post-peak metamorphism. • Transition from subduction-related to within-plate magmatism was concomitant with widespread aqueous-carbonic fluid flow. • Significant orogenic gold mineralization formed at ca. 600 Ma, concurrent with crustal exhumation and extensive shearing. [ABSTRACT FROM AUTHOR]

Abstract The Hunjiang basin in Jilin Province, China, is host to a NE-trending sequence of sedimentary rocks located along the northeastern margin of the North China block in the Paleoproterozoic Jiao-Liao-Ji belt. The North China block is the largest and oldest cratonic block in China, but unlike other Precambrian cratons, its eastern part has been decratonized by multiple Phanerozoic orogenic events. No comprehensive geochronology study has been conducted on the rocks of the Hunjiang basin, and both the mechanisms and timing of lithospheric delamination beneath the eastern part of the North China block are largely unconstrained. In the Hunjiang basin, Proterozoic to Paleozoic sedimentary rocks are intruded by Mesozoic granitoids and are overlain unconformably by sedimentary and volcaniclastic rocks. Twenty igneous rocks (granites, porphyritic rocks, and volcaniclastic rocks) from the basin were analyzed for whole-rock geochemistry and dated by U-Pb laser ablation-inductively coupled plasma-mass spectrometry of magmatic zircons. The samples collected are felsic to intermediate in composition and of calc-alkaline affinity, and the granitic and porphyritic rocks show an adakite-like geochemistry. With the exception of one Neoarchean granite dike with a 207Pb/206Pb age of 2524 ± 9 Ma that intrudes the basement along the northeastern margin of the basin, all igneous rocks dated in the present study have Mesozoic crystallization ages between 180 ± 1 Ma and 90 ± 2 Ma. The Precambrian inherited zircons show age peaks at ~2700 Ma, ~2650 Ma, and ~2500 Ma. The presence of inherited zircons with ages as old as 3387 ± 38 Ma (207Pb/206Pb ages) shows that Paleoarchean crust exists beneath the Proterozoic to Paleozoic sedimentary rocks of the basin. The geochronological results suggest that magmatic activity and associated formation of hydrothermal ore deposits in the Hunjiang basin were prevalent from the Middle Jurassic to the early Late Cretaceous. Furthermore, structural constraints on the cessation of major tilting in the basin are provided, as an Early Cretaceous (127 ± 1 Ma) flat-lying volcaniclastic rock unit unconformably overlies steeply dipping sedimentary rocks. The adakite-like geochemistry of most granitic and porphyritic rocks suggests partial melting of a delaminated eclogitic lower crust, whereas the higher MgO, Ni, and Cr content of the Early Cretaceous porphyritic rocks indicates reaction between adakitic melts and mantle peridotite. Many of the volcaniclastic rocks have more evolved, less adakitic signatures and show negative Eu anomalies, indicating these formed from more evolved melts at shallower crustal depths, accompanied by assimilation-fractional crystallization processes. The results of this study indicate that major delamination was completed in the Hunjiang basin by the Middle Jurassic, while delamination was ongoing into the Early Cretaceous in many other parts of eastern China. Graphical abstract Unlabelled Image Highlights • Magmatic U-Pb ages of igneous rocks from the Hunjiang basin are Early Jurassic to early Late Cretaceous. • One granite dike intruded into basement rocks yields a Neoarchean age. • Adakitic signatures are observed, particularly in the porphyritic and granitic igneous rocks. • Models for lithospheric delamination under the North China block are discussed. [ABSTRACT FROM AUTHOR]

Abstract: China's largest gold resource is located in the highly endowed northwestern part of the Jiaodong gold province. Most gold deposits in this area are associated with the NE- to NNE-trending shear zones on the margins of the 130–126Ma Guojialing granite. These deposits collectively formed at ca. 120±5Ma during rapid uplift of the granite. The Dayingezhuang deposit is a large (>120t Au) orogenic gold deposit in the same area, but located along the eastern margin of the Late Jurassic Linglong Metamorphic Core Complex. New 40Ar/39Ar geochronology on hydrothermal sericite and muscovite from the Dayingezhuang deposit indicate the gold event is related to evolution of the core complex at 130±4Ma and is the earliest important gold event that is well-documented in the province. The Dayingezhuang deposit occurs along the Linglong detachment fault, which defines the eastern edge of the ca. 160–150Ma Linglong granite–granodiorite massif. The anatectic rocks of the massif were rapidly uplifted, at rates of at least 1km/m.y. from depths of 25–30km, to form the metamorphic core complex. The detachment fault, with Precambrian metamorphic basement rocks in the hangingwall and the Linglong granitoids and migmatites in the footwall, is characterized by early mylonitization and a local brittle overprinting in the footwall. Gold is associated with quartz–sericite–pyrite–K-feldspar altered footwall cataclasites at the southernmost area of the brittle deformation along the detachment fault. Our results indicate that there were two successive, yet distinct gold-forming tectonic episodes in northwestern Jiaodong. One event first reactivated the detachment fault along the edge of the Linglong massif between 134 and 126Ma, and then a second reactivated the shears along the margins of the Guojialing granite. Both events may relate to a component of northwest compression after a middle Early Cretaceous shift from regional NW–SE extension to a NE–SW extensional regime. [Copyright &y& Elsevier]

Abstract: The Asian continent formed during the past 800m.y. during late Neoproterozoic through Jurassic closure of the Tethyan ocean basins, followed by late Mesozoic circum-Pacific and Cenozoic Himalayan orogenies. The oldest gold deposits in Asia reflect accretionary events along the margins of the Siberia, Kazakhstan, North China, Tarim–Karakum, South China, and Indochina Precambrian blocks while they were isolated within the Paleotethys and surrounding Panthalassa Oceans. Orogenic gold deposits are associated with large-scale, terrane-bounding fault systems and broad areas of deformation that existed along many of the active margins of the Precambrian blocks. Deposits typically formed during regional transpressional to transtensional events immediately after to as much as 100m.y. subsequent to the onset of accretion or collision. Major orogenic gold provinces associated with this growth of the Asian continental mass include: (1) the ca. 750Ma Yenisei Ridge, ca. 500Ma East Sayan, and ca. 450–350Ma Patom provinces along the southern margins of the Siberia craton; (2) the 450Ma Charsk belt of north-central Kazakhstan; (3) the 310–280Ma Kalba belt of NE Kazakhstan, extending into adjacent NW Xinjiang, along the Siberia–Kazakhstan suture; (4) the ca. 300–280Ma deposits within the Central Asian southern and middle Tien Shan (e.g., Kumtor, Zarmitan, Muruntau), marking the closure of the Turkestan Ocean between Kazakhstan and the Tarim–Karakum block; (5) the ca. 190–125Ma Transbaikal deposits along the site of Permian to Late Jurassic diachronous closure of the Mongol–Okhotsk Ocean between Siberia and Mongolia/North China; (6) the probable Late Silurian–Early Devonian Jiagnan belt formed along the margin of Gondwana at the site of collision between the Yangtze and Cathaysia blocks; (7) Triassic deposits of the Paleozoic Qilian Shan and West Qinling orogens along the SW margin of the North China block developed during collision of South China; and (8) Jurassic(?) ores on the margins of the Subumusu block in Myanmar and Malaysia. Circum-Pacific tectonism led to major orogenic gold province formation along the length of the eastern side of Asia between ca. 135 and 120Ma, although such deposits are slightly older in South Korea and slightly younger in the Amur region of the Russian Southeast. Deformation related to collision of the Kolyma–Omolon microcontinent with the Pacific margin of the Siberia craton led to formation of 136–125Ma ores of the Yana–Kolyma belt (Natalka, Sarylakh) and 125–119Ma ores of the South Verkhoyansk synclinorium (Nezhdaninskoe). Giant ca. 125Ma gold provinces developed in the Late Archean uplifted basement of the decratonized North China block, within its NE edge and into adjacent North Korea, in the Jiaodong Peninsula, and in the Qinling Mountains. The oldest gold-bearing magmatic–hydrothermal deposits of Asia include the ca. 485Ma Duobaoshan porphyry within a part of the Tuva–Mongol arc, ca. 355Ma low-sulfidation epithermal deposits (Kubaka) of the Omolon terrane accreted to eastern Russia, and porphyries (Bozshakol, Taldy Bulak) within Ordovican to Early Devonian oceanic arcs formed off the Kazakhstan microcontinent. The Late Devonian to Carboniferous was marked by widespread gold-rich porphyry development along the margins of the closing Ob–Zaisan, Junggar–Balkhash, and Turkestan basins (Amalyk, Oyu Tolgoi); most were formed in continental arcs, although the giant Oyu Tolgoi porphyry was part of a near-shore oceanic arc. Permian subduction-related deformation along the east side of the Indochina block led to ca. 300Ma gold-bearing skarn and disseminated gold ore formation in the Truong Son fold belt of Laos, and along the west side to ca. 250Ma gold-bearing skarns and epithermal deposits in the Loei fold belt of Laos and Thailand. In the Mesozoic Transbaikal region, extension along the basin margins subsequent to Mongol–Okhotsk closure was associated with ca. 150–125Ma formation of important auriferous epithermal (Balei), skarn (Bystray), and porphyry (Kultuminskoe) deposits. In northeastern Russia, Early Cretaceous Pacific margin subduction and Late Cretaceous extension were associated with epithermal gold-deposit formation in the Uda–Murgal (Julietta) and Okhotsk–Chukotka (Dukat, Kupol) volcanic belts, respectively. In southeastern Russia, latest Cretaceous to Oligocene extension correlates with other low-sulfidation epithermal ores that formed in the East Sikhote–Alin volcanic belt. Other extensional events, likely related to changing plate dynamics along the Pacific margin of Asia, relate to epithermal–skarn–porphyry districts that formed at ca. 125–85Ma in northeastmost China and ca. 105–90Ma in the Coast Volcanic belt of SE China. The onset of strike slip along a part of the southeastern Pacific margin appears to correlate with the giant 148–135Ma gold-rich porphyry–skarn province of the lower and middle Yangtze River. It is still controversial as to whether true Carlin-like gold deposits exist in Asia. Those deposits that most closely resemble the Nevada (USA) ores are those in the Permo-Triassic Youjiang basin of SW China and NE Vietnam, and are probably Late Triassic in age, although this is not certain. Other Carlin-like deposits have been suggested to exist in the Sepon basin of Laos and in the Mongol–Okhotsk region (Kuranakh) of Transbaikal. [Copyright &y& Elsevier]

The NWW-striking North Qilian Orogenic Belt records the Paleozoic accretion–collision processes in NW China, and hosts Paleozoic Cu–Pb–Zn mineralization that was temporally and spatially related to the closure of the Paleo Qilian-Qinling Ocean. The Wangdian Cu deposit is located in the eastern part of the North Qilian Orogenic Belt, NW China. Copper mineralization is spatially associated with an altered early Paleozoic porphyritic granodiorite, which intruded tonalites and volcaniclastic rocks. Alteration zones surrounding the mineralization progress outward from a potassic to a feldspar-destructive phyllic assemblage. Mineralization consists mainly of quartz-sulfide stockworks and disseminated sulfides, with ore minerals chalcopyrite, pyrite, molybdenite, and minor galena and sphalerite. Gangue minerals include quartz, orthoclase, biotite, sericite, and K-feldspar. Zircon LA-ICPMS U–Pb dating of the ore-bearing porphyritic granodiorite yielded a mean 206 Pb/ 238 U age of 444.6 ± 7.8 Ma, with a group of inherited zircons yielding a mean U–Pb age of 485 ± 12 Ma, consistent with the emplacement age (485.3 ± 6.2 Ma) of the barren precursor tonalite. Rhenium and osmium analyses of molybdenite grains returned model ages of 442.9 ± 6.8 Ma and 443.3 ± 6.2 Ma, indicating mineralization was coeval with the emplacement of the host porphyritic granodiorite. Rhenium concentrations in molybdenite (208.9–213.2 ppm) suggest a mantle Re source. The tonalities are medium-K calc-alkaline. They are characterized by enrichment of light rare-earth elements (LREEs) and large-ion lithophile elements (LILEs), depletion of heavy rare-earth elements (HREEs) and high-field-strength elements (HFSEs), and minor negative Eu anomalies. They have ε Hf ( t ) values in the range of +3.6 to +11.1, with two-stage Hf model ages of 0.67–1.13 Ga, suggesting that the ca. 485 Ma barren tonalites were products of arc magmatism incorporating melts from the mantle wedge and the lithosphere. In contrast, the 40-m.y.-younger ore-bearing porphyritic granodiorite is sub-alkaline and peraluminous. They are enriched in LREEs and LILEs, depleted in HFSEs, and show weak negative Eu anomalies. They display ε Hf ( t ) values of captured or inherited zircons in the range of +8.5 to +10.0, and younger two-stage Hf model ages of 0.78 Ga and 0.86 Ga, similar to those of ca. 485 Ma tonalite. The ca. 445 Ma zircons have ε Hf ( t ) values of −2.1 to +9.9, with two-stage Hf model ages of 0.75–1.27 Ga. Moreover, they have relatively high oxygen fugacity than that of the precursor barren tonalite. The ca. 445 Ma magmas at Wangdian thus formed in a subduction setting, and incorporated melts from the subduction-modified lithosphere that had previously been enriched by additions of chalcophile and siderophile element-rich materials by the earlier magmatism and metasomatism during the Paleo Qilian-Qinling Ocean subduction event. [ABSTRACT FROM AUTHOR]

The NNE-trending Linglong Metamorphic Core Complex hosts the majority of the gold deposits in the Jiaodong Peninsula of eastern China. Many of the deposits are hosted by the 163–155 Ma Linglong granite in the footwall of the Linglong detachment fault. Argon thermochronology suggests that the granite had cooled to 400 °C by 143 ± 1.5 Ma possibly as a result of normal movement on the detachment. Nine zircon fission track (ZFT) ages from samples collected along a NW–SE transect perpendicular to the central part of the Linglong detachment fault at the − 652 m level in the Xiadian deposit constrain the subsequent thermal evolution of Linglong Metamorphic Core Complex, which overlapped the period of major gold deposition. The ZFT ages vary from 136.9 ± 3.3 Ma (1σ) to 130.1 ± 2.2 Ma (1σ). The unaltered Linglong granite in the footwall and amphibolite in the hangingwall have similar ages at 136.9 ± 3.3 Ma (1σ) and 135.0 ± 3.0 Ma (1σ), whereas ages for the disseminated- and stockwork-style ores appear to be younger at ca. 131–130 Ma, although there is an overlap of ages when considering the 1σ precision. Interestingly, ZFT ages show no marked differences between the hangingwall and footwall of the Linglong detachment fault, although significant movement along the fault occurred. The results are best interpreted to indicate that the Linglong granite was emplaced at ~ 160 Ma, and cooled to 240 ± 50 °C at ~ 135 Ma, as recorded by unaltered rocks in the footwall. Hydrothermal alteration along the Linglong detachment fault led to annealing of zircon fission tracks and the consistent younger ages of ~ 131 Ma. Quartz aggregates associated with gold mineralization show evidence of recrystallization suggesting that the hydrothermal event was initiated at temperatures of at least 300–350 °C, near the brittle–ductile transition, but cooled rapidly to ZFT closure temperatures within a country-rock environment that was already relatively cool. Therefore these ZFT ages suggest that the timing of mineralization at the Xiadian deposit was post-135 Ma and likely very close to 131 Ma. The mineralization and cooling occurred in the footwall of a major detachment fault under an extensional regime, possibly related to the progressive slab rollback of the paleo-Pacific plate, and controlled by the Linglong Metamorphic Core Complex. [ABSTRACT FROM AUTHOR]

The Chah Bagh gold deposit, in the Muteh gold district, is located in the central part of the Sanandaj-Sirjan zone (SSZ), Iran. Gold mineralization at Chah Bagh is hosted by a Paleozoic sequence of rocks that is dominated by deformed schist, metarhyolite, and amphibolite that exhibits a greenschist- to lower amphibolite-facies metamorphism. Three deformation events are recognized in the Chah Bagh area, D, D, and D. The major NW-trending (N280-N290) dextral strike-slip shear zone in the area was formed during D ductile events. Gold mineralization at Chah Bagh occurred over a prolonged deformation history, but is closely related to alteration, retrograde greenschist-facies assemblages, and ductile and brittle deformation during D and D. The geometry of the Au-bearing quartz veins indicates that they are temporally related to the S foliation and therefore to the D flattening and shearing. Some veins, however, are spatially and temporally related to D brittle normal faults and are brecciated and boudinaged during the associated shear movement. The presence of deformed Au-bearing quartz veins, and their concordant and discordant relation with respect to the main mylonitic foliation and the shear zone, indicates continuous mineralization during the D episodes. The Au-hosting shear zones are characterized by extensive development of heterogeneous mylonitic rocks that enhanced the permeability within the shear zones. This gave rise to further extensive dilatancy within major dilational jogs and produced a suitable structural regime for vein-hosted Au mineralization. The epigenetic Au mineralization resulted from metamorphic hydrothermal fluids circulating through major shear zones and associated structures during the late stages of orogeny. Our investigation shows that granitic intrusions have no genetic link with gold mineralization and we propose an orogenic gold model for Chah Bagh deposit, similar to Qolqoleh and Kervian in the northwestern part of the SSZ. This model is consistent with a dextral transpressional deformation kinematic model along the SSZ and, refutes the previous intrusion-related model suggested for the Muteh gold deposits. Metamorphic devolatilization and fluid flow within a ca. 30-m.y.-long period in Late Cretaceous and Early Tertiary is suggested for the genesis of the gold occurrences in both ductile and post-transpressional brittle structures. [ABSTRACT FROM AUTHOR]

Abstract: The south-central part of the Greater Caucasus region, Georgia Republic, represents an extremely prospective region for significant orogenic gold deposits. Gold-bearing quartz veins are concentrated in two extensive WNW-trending belts, the Mestia-Racha and Svaneti districts, within the northern margin of the Southern Slope Zone of the Great Caucasus orogen. This metalliferous region is dominated by Early to Middle Jurassic slates, which are part of a terrane that likely accreted to the continental margin from late Paleozoic to Jurassic. The slates were subsequently intruded by both Middle to Late Jurassic and Neogene granitoids. Quartz veins in the more carbonaceous slate units are most consistently enriched in As, Au, Hg, Sb, and W, and show mineralization styles most consistent with typical orogenic gold deposits. Quartz veins in the Mestia-Racha district were mined in Soviet times for As, Sb, and W, but many of these are now being recognized as gold resource targets. The veins occur in the footwall of a thrust fault between the Southern Slope zone and an earlier accreted terrane, the Main Zone, to the north. Many veins in the district continue along strike for >1 km and some cut Neogene intrusions, constraining ore formation to the most recent 4 to 5 million years. Gold deposition thus correlates with final collision of the Arabian plate to the south and uplift of the ore-hosting Greater Caucasus. The Zopkhito deposit, previously mined for antimony, contains an estimated 55 t Au at a cutoff grade of 0.5 g/t. The veins are localized in an area where smaller-order structures show a major change in strike from N–S to more E–W trends. A pyrite–arsenopyrite ore stage includes gold concentrated in both sulfide phases; it is overprinted by a later stibnite-dominant stage. Fluid-inclusion studies of ore samples from the Zopkhito deposit indicate minimum trapping temperatures of 300 to 350 °C and 200 to 300 °C for the two stages, respectively, and minimum trapping pressures of 0.2 to 0.5 kbar. Ore-forming fluids, with approximately 5 to 20 mol% non-aqueous gas, evolved from N2-dominant to CO2-dominant during evolution of the hydrothermal system. δ 34S values of +1 to +4‰ for ore-related sulfides at Zopkhito are consistent with a sedimentary rock source for the sulfur, and δ 18O quartz measurements of 16 to 21‰ are consistent with either a magmatic or metamorphic fluid. More than 60 gold-bearing lodes and placers in the Svaneti district occur along the thrust between the Southern Slope and Main Zones. Lode gold potential was first recognized in the historic placer district in the 1980s, with many auriferous quartz veins cutting Middle Jurassic igneous rocks. Brecciated veins in the 18 t Au Lukhra deposit cut a small granodioritic to dioritic stock; the latter intrudes Devonian schist immediately north of the thrust. Presently, there are three recognized ore zones in the deposit, with the most significant occurring over an area 140 m in length and 12 m-wide, with typical grades of 7 to 9 g/t Au. Reconnaissance fluid-inclusion studies of ore samples from the Lukhra deposit indicate minimum trapping temperatures of 220 °C. Measurements of δ 18Oquartz of about 10‰ suggest buffering of isotopic composition by the igneous host rocks. [Copyright &y& Elsevier]