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The North China Craton (NCC), which underwent multiple subduction and lithospheric destruction during the Mesozoic, is well known for hosting some of the world-class gold deposits. In many cases, Mesozoic mafic dykes are associated with the gold deposits, although there has been no systematic studies aimed to integrate the characteristics of these dykes in different regions of the NCC. Here we investigate diabase and lamprophyre dyke suites in the Xiaoqinling region along the southern margin of the NCC, and compile the published geochronological, geochemical and isotopic data for regional mafic dykes and gold deposits from the major gold belts including Jiaodong, Xiaoqinling and central NCC. Zircon U-Pb data show the mafic dykes in Xiaoqinling were emplaced in two episodes at 219–227 Ma and 121–137 Ma, and their εHf(t) values (ranging from −2.1 to 3.8 and −13.6 to 1.6 respectively) suggest increasing input of lithospheric materials in the Early Cretaceous dykes. The compiled geochemical data on the mafic dykes from different regions in the NCC show that the magmatic evolution involved olivine and clinopyroxene fractional crystallization with limited crustal contamination and subduction-related fluid metasomatism. The geochemical and isotopic signature suggests multiple sources for the parent magma of the mafic dykes ranging from convective asthenospheric mantle to ancient lithospheric mantle, with the magma source characterized by enriched mantle (EM2 or EM2+ EM1), and that signatures might be potential for gold mineralization. Further, most dykes are coeval and cospatial with gold deposits in the NCC. The geochronological data show that small amount of both Mesozoic dykes and gold deposits formed in Triassic whereas the peak formed in Cretaceous following slab roll back of the Pacific plate subducting from the east during 145–110 Ma. We envisage that the tectonic extension associated with Pacific slab subduction contributed to the magmatism and gold mineralization in the NCC. [ABSTRACT FROM AUTHOR]

The Yixingzhai gold deposit is a quartz‐vein–type deposit accompanied by skarn iron and porphyry molybdenum mineralization. There are four crypto‐explosive breccia pipes which provide an important ore‐controlling structure. Here we investigate the composition and compositional zoning of the native gold, garnet, and epidote in the Tietangdong skarn breccia pipe through detailed petrography, electron probe microanalysis, and elemental mapping. The native gold compositions show that they were formed in a relative higher temperature condition. Based on their composition and optical characteristics, the zoning in garnet can be divided into three types. The garnets of Generations 1 and 3 show high contents of spessartine (2.91–10.17 mol%) and grossular (20.94–54.71 mol%) and anomalous birefringence, indicating that they formed under relatively higher pressure and temperature and lower oxygen fugacity. The garnets of Generation 2 are mainly composed of andradite (75.70–99.98 mol%) and show compositional homogeneity, with formation under relative lower pressure and temperature and higher oxygen fugacity conditions. Magmatic‐hydrothermal pulses and multiple crypto‐explosions could be the main geological processes that caused the formation of the zoning textures. Zoning in epidote is more complex than that in garnet, and from core to the rim, the iron content shows an abrupt increase and aluminium content shows decrease. There is also decrease in iron and increase in aluminium in the inner part. These features might record multiple crypto‐explosion processes. Combining the complex replacement features of iron oxides and sulphides in the breccia pipe, we suggest that the Tietangdong breccia pipe formed through several crypto‐explosions. The fluid system in the breccia pipe activated during multiple crypto‐explosions, and oxygen fugacity varied greatly, which was disadvantageous to the accumulation and precipitation of ore‐forming elements. Crypto‐explosions destroyed the ore bodies formed during the early stage, resulting in their scattered distribution throughout the breccia pipe. Cone fractures formed eventually with the shrinking of the cooling breccia pipe after the magmatism ceased. Those fractures provided important ore‐hosting structures for the gold mineralization during the late stage. Our research indicates that there is high prospecting potential for porphyry Mo, Cu, and Au deposits in the deeper domains of the breccia pipes. [ABSTRACT FROM AUTHOR]

The Shihu quartz vein‐type gold deposit in the central North China Craton occurs within Neoarchean TTG (tonalite‐trondhjemite‐granodiorite) gneisses and shows spatial relationship with quartz diorite porphyry. The occurrence of the ore body is controlled by the N‐S fracture. Primary mineral assemblage of the ore body is composed of quartz, calcite, and base‐metal sulphides, including pyrite, galena, sphalerite, chalcopyrite, and pyrrhotite. Eight pyrite samples from veins of the main mineralization stage yield an isochron age of 129 ± 3 Ma (MSWD = 1.6), coinciding with the major Early Cretaceous magmatic event, and associated lithospheric thinning recognized in the NCC. The (87Sr/86Sr)i values of the pyrite (0.7102 ± 0.0006) are lower than the continental crust mean value (0.719) and higher than that of the mantle initial ratio (0.707), suggesting mixed crust–mantle source for the metallogenic components. Three types of hydrothermal pyrite from the early to major ore‐forming stages were identified in the quartz vein, including Py(I) as disseminated euhedral grains, Py (II) as dense bulks, and Py (III) as intergrowth with base‐metal sulphides. Electron microprobe analysis of the pyrite grains indicates a trend from S‐deficient to S‐enriched and from Fe‐enriched to Fe‐deficient stages, suggesting an increase in sulphur fugacity and reducing conditions. The arsenic in pyrite shows decrease against increasing Au during Stages II and III, implying that As is not the only trigger of gold precipitation, but electrochemical‐geochemical barrier played a major role in the formation of the ore. The Co and Ni concentrations, as well as Co/Ni ratios in pyrite, are relatively high, which provide an additional clue to the link with the regional magmatic event. Combined with the textural features, we propose a wider potential for gold exploration in this region, linking the mineralization with a major transitional tectonic regime. [ABSTRACT FROM AUTHOR]

The Bagrote and Dainter valleys in Gilgit Baltistan Pakistan, belonging to the Kohistan island arc and southwestern domain of the Karakorum metamorphic complex, respectively, are a location of regional placer gold mining. However, no in situ hydrothermal gold deposits have been discovered in this region. Here, we report the textural, morphological, and geochemical characteristics of placer gold from the stream sediments of the Bagrote and Dainter valleys with a view to trace the provenance. The morphological features of the studied gold grains indicate proximal source mineralization. The gold grains display a microtexture typical of mechanical abrasion rather than chemical activity. Their chemical composition of most of the grains from each stream falls in a restricted range (minor alloying elements mainly Cu) with high fineness (1,000 Au/(Au + Ag)), suggesting derivation from a homogeneous source or limited number of mineralization types. The high Cu content of the gold grains from the Bagrote stream suggests that the gold here might be associated with previously undiscovered porphyry gold mineralization, whereas the Au–Ag–Hg alloys from the Dainter stream suggest a genetic linkage with undiscovered fault‐controlled auriferous veins of epithermal origin in the southwestern part of the Karakorum metamorphic complex. The chemical composition of both streams placer gold in triangular diagram in terms of Au–Ag–Cu shows all the gold grains from Dainter stream were derived from epithermal type of mineralization, and most of the plots of Bagrote stream fall on the domain of porphyry epithermal type of deposits which are also in consistent with a continental arc setting in the study area. The mechanically developed microtexture, homogeneous chemical composition in individual grains from core to rim, and absence of high fineness rims of the gold grains from both streams, suggest the absence of any supergene regrowth and direct transfer from the primary source through glacier to the fluvial system. The Gilgit Baltistan province, dominated by dry temperate climate and glacial environment having steep geomorphology, precluding any significant supergene processes such as silver leaching and addition of authigenic gold on detrital gold grains. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The Diaoquan Ag-Cu deposit formed at about 130 Ma, during the peak stage of the destruction of NCC. • The metallogenic components were sourced from both mantle and crust. • The inner and deeper domains of the intrusions have good potential for future prospecting. Abstract The North China Craton (NCC) has been the focus of investigations on metallogeny in relation to craton destruction. The Diaoquan Ag-Cu polymetallic skarn mineralization is one of the large Ag deposits in central NCC. Here we present new mineralogical, geochronological and geochemical data from this deposit with the objective to gain an insight into the magmatic hydrothermal processes in relation to decratonization. The timing of polymetallic mineralization in this deposit is constrained as ca. 130 Ma by phlogopite Ar-Ar and molybdenite Re-Os dating. The physico-chemical conditions of the magmatic evolution estimated from amphibole, biotite, magnetite-ilmenite mineral thermobarometer indicate that the monzonite and porphyritic granite magma developed in a magma chamber at a palaeoburial depth of 2–3.3 km, and was subsequently emplaced at 1–2 km palaeodepth. The oxygen fugacity conditions were relatively high (>ΔNNO + 1.6 buffer) in the early stage and rapidly dropped (<ΔFMQ buffer). The major and trace element features suggest magma mixing as a possible mechanism that generated the different intrusions. Sr-Nd-Pb and zircon Hf isotope data indicate that lower crust is the major source of the magma and that part of metallogenic elements might have been sourced from mantle-derived components. We constructed the magmatic hydrothermal system as follows: (1) mafic magma formed by the partial melting of thinned mantle lithosphere; (2) the mafic magma underplating resulted in the partial melting of the lower crust, and generated granitic magma; (3) mixing of the mafic and felsic magmas generated the intermediate magma; (4) ore-forming fluids from the magma chamber migrated into the contact zone through fractures, resulting in Ag-Cu mineralization by skarnization; and (5) Mo-bearing fluid separated from the granite magma deposited the molybdenite in the inner contact zone. [ABSTRACT FROM AUTHOR]

The widespread tectonic and magmatic events in Southeast China during the Mesozoic were accompanied by large‐scale metallogenesis. Here, we investigate the petrology, geochemistry, and zircon U–Pb age of the porphyry dykes in relation to the gold mineralization at Dongyang deposit in the Fujian Province. The geochemical data show silica‐rich and Mg‐ and Ca‐poor A‐type granite affinity for the dykes. The rocks have high concentrations of Light Rare Earth Elements (LREE) and Large Ion Lithophile Elements (LILE) and relatively low contents of Heavy Rare Earth Elements (HREE) and High Field Strength Element (HFSE). They display (La/Yb)N and (La/Sm)N values in the range of 5.7 to 31.4 and 6.0 to 8.3, respectively, with negative anomalies of Ba, Nb, Ta, Sr, Zr, Eu, and Ti and positive Ce anomaly. The source magma for the dykes was derived from a mixture of partially melted Al‐rich crustal material, with an input of mantle components. We present sensitive high‐resolution ion microprobe zircon U–Pb data from the dykes, which show emplacement ages in the range of 158 to 162 Ma, coinciding with the onset of the Yanshanian magmatism in Southeast China. Integrating the data obtained from studies on geology, geochronology and petro‐geochemistry, we suggest that the dykes played role in controlling the gold mineralization, and the magmatism and gold mineralization are the response of continental lithosphere thinning in Southeast China triggered by the subduction of the ancient Pacific Ocean Plate. [ABSTRACT FROM AUTHOR]

The Yixingzhai and Xinzhuang gold deposits are the most important gold mineralization of the Wutai-Hengshan region in the center of the North China Craton (NCC). Here we present new geological, mineralogical, geochemical and geochronological evidence from these deposits with a view to formulate a comprehensive model for the Mesozoic magmatism and metallogeny in the NCC. Our Re-Os dating of molybdenite from the Hewan granite porphyry constrains the timing of mineralization as 142 Ma. Gold mineralization occurred in the late stage of magmatism with close temporal and spatial relationships with the Sunzhuang pluton. Intensive parameters using amphibole, biotite, magnetite-ilmenite mineral thermobarometry and oxygen fugacity indicate that the parental magma for the Sunzhuang pluton evolved at high oxygen fugacity (>NNO + 2 buffer), and was emplaced at a depth of 2–2.6 km. The He-Ar isotopic composition of the fluid inclusions from pyrite grains in the Yixingzhai gold deposit suggests the involvement of mantle-derived fluids although the Pb isotope data shows that ancient lower crust is the major source. The major and trace element features, Sr-Nd-Pb and zircon Hf isotope data coupled with available geophysical information suggest that magmatism and mineralization in this region witnessed the interaction of mantle-derived mafic magmas with lower crust, with the latter as the major source. The magmatic and metallogenic processes involved the following: (1) partial melting and production of mafic magma triggered by upwelling asthenosphere; (2) mafic magma underplating under lower crust and partial melting of the ancient lower crust generated granitic magma; (3) formation of intermediate magma through the interaction between mafic and felsic magmas; (4) separation of ore-forming fluids from the Sunzhuang pluton and their migration through fault zones in the shallow crust generating the gold mineralization. [ABSTRACT FROM AUTHOR]

Located in the eastern section of the Central Asian Orogenic Belt, the Jiawula Ag-Pb-Zn deposit is classified as a volcanic to subvolcanic related vein-type ore deposit. New U-Pb zircon geochronology, whole-rock geochemistry, mineral chemistry, and Sr-Nd isotope data are presented for the intrusions in the Jiawula deposit in order to evaluate the timing, petrogenetic type of the granitoid rocks, origin and evolution of magmatism, geodynamics, and to establish its relationship with lead-zinc mineralization. Zircon SHRIMP U-Pb analyses yield weighted mean ages of 150.1 ± 1.8 Ma for quartz porphyry, 148.8 ± 2.2 Ma for syenite porphyry, and 145.3 ± 1.9 Ma for monzonite porphyry, indicating a Late Jurassic (Yanshanian) magmatic event. An earlier magmatic event (Indosinian) occurred during the Late Permian to Early Triassic from ca. 254 Ma to ca. 247 Ma and is represented by granodiorite (254 ± 2 Ma), dacite porphyry (252.9 ± 4.8 Ma), and diorite porphyry (278 ± 4.1 Ma). Both the Indosinian and Yanshanian igneous rocks are classified as I-type granitoids. The late Jurassic intrusions are highly fractionated and characterized by negative anomalies of Eu, Sr, P, and Ti. The hypabyssal intrusions have initial 87 Sr/ 86 Sr values between 0.70458 and 0.70522, and ε Nd (t) values of −3.4 to −0.2, indicating relatively older crust in Jiawula among more juvenile crust in this area. Magma generation in Jiawula is linked to juvenile lower crustal and slightly enriched mantle sources. The ∼250 Ma magmatic episode in Jiawula might be related to the subduction of the Mongol-Okhotsk oceanic plate towards the south beneath the Erguna massif. The ∼150 Ma magmatic event occurred after the closure of the Mongol-Okhotsk Ocean followed by the change in subduction direction of the Paleo-Pacific plate. Varying temperature, stronger fractionation and higher oxygen fugacity related to the magmatic-hydrothermal transition caused Pb-Zn mineralization. [ABSTRACT FROM AUTHOR]

The Han-Xing region is located in the south Taihang Mountains (TM) in the central part of the North China Craton, and is an important iron producing area. The iron deposits in this region are of skarn type, related to an Early Cretaceous high-Mg diorite complex, including gabbro diorite, hornblende diorite, diorite, diorite porphyrite, and monzonite. In this study we report the detailed mineral chemistry of the high-Mg diorites and skarn rocks. The olivine in the gabbro diorite shows chemical composition similar to that in mantle peridotite xenoliths. Clinopyroxene in the gabbro diorite is dominantly augite, with only minor diopside, whereas the clinopyroxenes in the diorite and monzonite are diopside. Amphiboles in the high-Mg diorites show compositional range from magnesiohornblende to magnesiohastingsite, with minor pargasite and tschermakite. Most plagioclase in the high-Mg diorite is andesine and oligoclase. The magnesio-biotite in gabbro diorites shows chemical characteristics of re-equilibrated primary biotites and those in calc-alkaline rocks. In the diorite and diorite porphyrite, plagioclase shows complex chemical zoning. Clinopyroxene and garnet in skarn rocks show varying FeO contents, the former containing low FeO (< 9 wt.%) and occurring as the major skarn mineral in large-scale iron deposits, and the latter within small-scale iron deposits with high FeO (mostly > 25 wt.%) content. We computed the pressure, temperature, oxygen fugacity and water contents based on the mineral chemistry of amphibole and biotite. Based on the results, the magma crystallization can be divided into two stages, one within the deep magma chamber, forming clinopyroxene, amphibole and plagioclase phenocrysts; the other after emplacement, forming the rim of phenocrysts and matrix minerals. The magma during the early stage shows high temperature (~ 900 °C–950 °C), pressure (~ 300 MPa–500 MPa), relatively high logfO 2 (NNO–NNO + 2), and H 2 O content in melt (4%–8%). During the late stage, the magma temperature dropped to about 750 °C, and pressure came down to less than 100 MPa, with the logfO 2 rising to NNO + 1–NNO + 2. The zoning of amphibole and plagioclase records the process of magma mixing and crystallization, with injection of mafic magma into the felsic magma chamber. The relatively high logfO 2 and H 2 O content inhibited partitioning of iron into mafic minerals and favored concentration of Fe in the melt. Iron ore precipitation occurred when the magma was emplaced at shallow level, and was principally controlled by the chemical composition of carbonate wall rocks. The high logfO 2 , Fe 3 + rich ore-forming fluid generated andradite and clinopyroxene when it reacted with limestone and dolomitic limestone respectively. [ABSTRACT FROM AUTHOR]

The Jilongshan skarn Cu-Au deposit is located at the Jiurui ore cluster region in the southwestern part of the Middle-Lower Yangtze River valley metallogenic belt. The region is characterized by NW-, NNW- and EW-trending faults and the mineralization occurs at the contact of lower Triassic carbonate rocks and Jurassic granodiorite porphyry intrusions. The intrusives are characterized by SiO2, K2O, and Na2O concentrations ranging from 61.66 to 67.8 wt.%, 3.29 to 5.65 wt.%, and 2.83 to 3.9 wt.%, respectively. Their A/CNK (A/CNK = n(Al2O3)/[ n(CaO) + n(Na2O) + n(K2O)]) ratio, δEu, and δCe vary from 0.77 to 1.17, 0.86 to 1, and 0.88 to 0.96, respectively. The rocks show enrichment in light rare earth elements ((La/Yb)N = 7.61-12.94) and large ion lithophile elements (LILE), and depletion in high field strength elements (HFSE), such as Zr, Ti. They also display a peraluminous, high-K calc-alkaline signature typical of intrusives associated with skarn and porphyry Cu-Au-Mo polymetallic deposits. Laser ablation inductively coupled plasma spectrometry (LA-ICP-MS) zircon U-Pb age indicates that the granodiorite porphyry formed at 151.75 ± 0.70 Ma. A few inherited zircons with older ages (677 ± 10 Ma, 848 ± 11 Ma, 2645 ± 38 Ma, and 3411 ± 36 Ma) suggest the existence of an Archaean basement beneath the Middle-Lower Yangtze River region. The temperature of crystallization of the porphyry estimated from zircon thermometer ranges from 744.3 °C to 751.5 °C, and 634.04 °C to 823.8 °C. Molybdenite Re-Os dating shows that the Jilongshan deposit formed at 150.79 ± 0.82 Ma. The metallogeny and magmatism are correlated to mantle-crust interaction, associated with the subduction of the Pacific Plate from the east. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Quartz-vein type gold mineralization at Xishimen is a recently discovered gold deposit in the central North China Craton. More than 50 auriferous quartz veins occur in this region within a NNW–SSE-trending fault zone 4600 m in length and 3–10 m wide. Wall rocks are mainly Precambrian tonalite–trondhjemite–granodiorite (TTG) gneisses and associated supracrustals, modified by K-feldspathization and pyrite-phyllic hydrothermal alteration. Based on detailed field and petrographic studies, we identify five episodes of mineralization: pyrite-phyllic stage (I), coarse-grained pyrite-milky white quartz stage (II), fine-grained smoky grey quartz-pyrite stage (III), fine-grained smoky grey quartz-polymetallic sulphide stage (IV), and quartz-carbonate stage (V). We present results of δ34S analysis of sulphide minerals from the different stages which show tightly clustered values in the range of –1.0‰ to 2.1‰, close to those of mantle and meteorite sulphur. Lead isotopic ratios of pyrite from the early to main stages also show restricted ranges with206Pb/204Pb of 16.289–17.286,207Pb/204Pb of 15.217–15.453,208Pb/204Pb of 37.012–38.232, implying lower crustal input.3He/4He and40Ar/36Ar ratios of fluid trapped in pyrite are 0.68 Ra to 1.20 Ra (where Ra is the3He/4He ratio of air = 1.4 × 10−6) and 540.9–1065, respectively.3He and4Ar concentrations vary from 10.05 to 18.5 (10−7 cm3STP/g) and 6.15 to 17.4 (10−7cm3STP/g), respectively, with calculated mantle helium ranging from 8.47% to 14.96% (average 11.01%). δ18OQand δ18DQvalues of quartz range from 8.0‰ to 13.2‰ and –101.9‰ to –70.5‰, respectively, with calculated δ18OWvalues of the mineralizing fluid ranging from 1.11‰ to 5.72‰, suggesting the mixing of magmatic aqueous fluid with meteoric water during gold precipitation. We correlate the mixed crust–mantle signature of the ore-forming sources to magmatism and metallogeny associated with Mesozoic inhomogeneous lithosphere thinning in the central North China Craton. [ABSTRACT FROM AUTHOR]

The Jinchang gold deposit is located in the easternmost portion of the Central Asian Orogenic Belt (CAOB), and represents one of the major gold districts in eastern Jilin–Heilongjiang provinces of China. The gold ore bodies are hosted mainly in altered Mesozoic granitoids, breccia pipes and ring and radial faults. Gold mineralization consists of alteration (stockwork in hydrothermally altered granites), breccia, and quartz-sulfide vein-types. Alteration assemblages around the alteration-style ore body show a vertical sequence of potassic, phyllic, and propylitic zones. In this study, we present U–Pb and Lu–Hf isotope data on zircons derived from mineralized granophyric granite, biotite monzogranite, granodiorite, and granite porphyry, and sericite Rb–Sr ages from the Jinchang gold deposit. The results show 206Pb/238U ages of 201±3Ma (MSWD=1.1), 203±4Ma (MSWD=1.4), 201±5Ma (MSWD=2.1), and 110±3Ma (MSWD=1.6), respectively. Sericite from the gold-mineralized phyllic-altered granodiorite and granite porphyry returns Rb–Sr isochron ages of 110±4Ma (MSWD=1.04) and 107±5Ma (MSWD=0.91), respectively. Our new data indicate that the gold mineralization at Jinchang took place at ca. 110Ma and was temporally related to intrusion of the granite porphyry. Zircon ε Hf (200Ma) values of the ca. 200Ma granites vary from −4.8 to +8.1, with TC DM model ages of 727–1535Ma, reflecting their derivation mainly by partial melting of juvenile Proterozoic crust. The gold-bearing 110Ma granite porphyry returns ε Hf (110Ma) values in the range of −1.6 to +9.8, with TC DM model ages of 542–1069Ma, suggesting partial melts of juvenile Proterozoic crust with notable input of mantle components as compared to the ca. 200Ma granites. Compiled oxygen (δ18OSMOW =−0.7–10.1) and hydrogen (δDSMOW =−99 to −70) stable isotopic values of quartz from ores indicate that the ore-forming fluids were predominantly exsolved from magmas with minor amount of meteoric water in quartz-sulfide veins at the late stage. The Hf isotope data from the granite porphyry, integrated with the results from previous data on S and Pb isotopic composition of ores, constrain the source of ore-forming components as lower crust with discernible mantle inputs and wall rock assimilation. Our results have implications bearing on the widespread magmatism and metallogenic event during the Early Cretaceous time in East China, and link them to mantle upwelling that contributed both heat and volatiles for crustal melting and scavenging of metals which in turn were concentrated in upper crustal levels through exsolution for the magmas. [ABSTRACT FROM AUTHOR]

• Porphyry and epithermal type of gold deposits in the hinterlands of the Bagrote valley. • Proximal source and high content of gold in pyrite suggest probable mineralization beneath the current level of erosion. • Gold occurs in pyrite in the form of micro to nano inclusions as Au0 instead of Au+1. • Ore forming fluids were derived from orogenic belts with minor contribution of lower crust. The Bagrote valley in North Pakistan, belonging to the Kohistan island arc, is well-known for regional placer gold mining. However, no economically feasible in situ hydrothermal gold deposits have been discovered in this region due to rugged terrain and remote nature of its location in the western Himalaya. The streams draining the Main Karakoram Thrust (MKT)/Shyoke suture zone carry placer gold in sediments as well as old river terraces, although the primary source remains unknown. In this paper, we employ a multiparametric approach including, X-ray Diffraction (XRD) analysis, thermoelectricity, major and trace element geochemistry and isotopic characteristics of pyrite associated with placer gold with a view to identify the nature of the unknown deposits and ore forming fluids on the catchment of the Bagrote valley. Pyrite in the Bagrote valley placers is euhedral to subhedral indicating the proximal gold sources. The high rate of occurrence of N-type thermoelectric coefficients (89%) with low P-type (11%) and crystallization temperature (290 °C−380 °C) combined with chemical features indicate that the pyrite was derived from porphyry or epithermal type of magmatic hydrothermal gold deposits from the hinterlands of the Bagrote valley. The X-Ray elemental maps show that Fe, As, Mo and Ni are homogenously distributed from core to rim suggesting stable crystallization condition without any alteration by later fluids. The calculated chemical formula of pyrite of our samples is [Au0.0006Fe] S2.004], plots of Au-As and Au-Fe shows that gold occurs in pyrite as micro to nano inclusion as Au0. The δ 34 S V - CDT values of pyrite range from – 0.6‰ to 0.9‰ with an average of −0.02‰, indicating the derivation of sulfur from a homogeneous magmatic source. The Pb isotope data indicates that the Pb was sourced from orogenic-type source, with minor contribution of lower crust. The narrow variations in 206Pb/204Pb and 208Pb/204Pb values suggest a single lead source. The low, medium and high Mo/Ni ratios reflect a mixed provenance for the auriferous pyrite. The average value of γ (71.8%), of pyrite computed from thermoelectric parameters (XnP), suggests that the dominant part of the primary source that contributes to the placers might have already been eroded. However, the proximal source and with high content of gold in the pyrite grains (up to 1160 ppm) suggest the possibility of significant economic mineralisation below the present erosion level of the deposits in the hinterlands of Bagrote Valley. [ABSTRACT FROM AUTHOR]

The Jiaodong type comprises a unique class of gold mineralisation which includes the Linglong type quartz-vein hosted and the Jiaojia type fracture-disseminated style deposits. Although the type area is in the Jiaodong Peninsula in NE China, where some of the world's richest gold reserves occur, we identify similar occurrences in other parts of China and elsewhere in the world under this category. The ore fluids migrated upwards forming quartz vein type of gold ore (Linglong type) wherever the ore-controlling fractures are at high angles. Fluid infiltration into the surrounding wall rocks and generation of the Jiaojia type disseminated style deposits resulted where the ore-bearing fluids encountered low angle fractures. On a regional scale, the Jiaodong type gold mineralisation occurs along the margins of reactivated cratons, within the interior of cratons along paleosuture zones, or along the junctions of micro-blocks, and is distinctly different from the classic orogenic gold in terms of their tectonic setting, ore characteristics and genetic history. Unlike skarn and porphyry type of deposits, the Jiaodong type gold deposits do not always show close spatial relationship with magmatic intrusives and some of the deposits occur distal to plutons (> 10 km). In this paper, we evaluate the salient geological, geochronological, geochemical and isotopic features of the Jiaodong type gold deposits and propose some general guidelines for gold prospecting. Based on case studies, we predict that the gold lodes in the Jiaodong type mineralised zones might extent vertically up to 3000 m with only minor mineralogical and geochemical variations. [ABSTRACT FROM AUTHOR]

[Display omitted] • Apatite from both the Huashan and Wenyu plutons are fluorapatite of magmaticorigin. • Wenyu apatite formed under a higher oxidation state and incorporated more mantle-derived materials than Huashan apatite. • Wenyu apatite crystallized earlier than feldspar and Huashan apatite was affected byfeldsparcrystallization. • The magma of the Wenyu pluton incorporated more intensive fluid exsolution during crystallization. • Wenyu pluton is more favorable to gold mineralization than the Huashan pluton. The relationship between granitic magmatism and lode gold mineralization has remained as a controversial topic among economic geologists. In this paper, we report in situ elemental and Sr isotopic signature of apatite from the Wenyu and Huashan granitic plutons in the Xiaoqinling goldfield, southern margin of the North China Craton (NCC), intending to provide further constrain the relationship between magmatism and metallogeny. The formation ages of Huashan and Wenyu granitic plutons are coeval with the gold mineralization, but most of the gold deposits are clustered nearing the Wenyu pluton, and only a few small gold deposits are found adjacent to the Huashan pluton. Although apatite from both plutons is all fluorapatite, characterized by negative Eu anomaly and enrichment of LREEs, the apatite from the two plutons shows different signatures. Based on these differences, the apatite from the Huashan pluton is divided as group A (HS-A) and group B (HS-B). The δEu, δCe values and MnO and Ga contents of the Wenyu and HS-A apatite indicate high oxygen fugacity range from MH to NNO for the magma, whereas the HS-B apatite shows low oxygen fugacity range from NNO to FMQ. The 87Sr/86Sr, REE, Th/U, and Ce/Y values of the apatite suggest that the magma for the Wenyu pluton incorporated more mantle-derived materials in contrast to Huashan pluton. Sr/Y ratio and REE content of the apatite indicate that WY apatite crystallized earlier than feldspar and Huashan apatite was affected by feldspar crystallization. The fluid-volatiles exsolution texture and S content of the apatite indicate higher content of volatiles in the Wenyu pluton magma, where the magma experienced more intense fluid exsolution than that of the Huashan pluton during apatite crystallization. The characteristics of many mantle-derived materials, high oxygen fugacity, and higher volatiles as revealed by the apatite data show that the magmatism of Wenyu pluton was more conducive to the mineralization of gold deposits than that of the Huashan pluton and is more closely related to gold deposits. [ABSTRACT FROM AUTHOR]

[Display omitted] • This study deepens understanding of the spatial and temporal evolution of minerals in the Bayan Obo Deposit. • Detailed mineralogical assemblages and fabric features of each ore are presented. • This study established the formation mechanism of different REE-Nb-Fe minerals and the metallogenic process of the deposit. The Bayan Obo deposit in the northern margin of the North China Craton is a world-class REE-Nb-Fe deposit, the complex mineralization history of which remains unresolved. In this study, we employ SEM and Image J software combined with mineralogical data obtained by in-situ EDS and EPMA analyses to analyze petrographic images rapidly and to investigate the mineralogical assemblages of each type of rocks/ores from the Main Orebody in an attempt to understand the mineralization process and ore-formation mechanism of this deposit. We identify three metallogenic periods and six ore-forming stages based on the field occurrence of ores combined with published geochronological data. The Mesoproterozoic magmatic event comprises two stages, which were distinguished as the coarse-grained dolomite stage (stage 1) and the fine-grained dolomite stage (stage 2). Three stages were recognized in the Mesoproterozoic shear deformation-hydrothermal mineralization period, including the disseminated mineralization stage (stage 3), the banded mineralization stage (stage 4) and the massive mineralization stage (stage 5). The Paleozoic hydrothermal period involved the vein mineralization stage (stage 6). Based on detailed studies of the mineral assemblages and paragenesis, as well as the complex textures of the ores, we propose a model of the multi-stage metallogenic process as follows: (1) The REE minerals and rutile occurring as inclusions wrapped within magmatic idiomorphic dolomite grains indicate that the REE-Nb mineralization might have started during the magmatic period. (2) The Nb minerals, such as fergusonite and ilmenorutile, intergrown with REE minerals, such as monazite and bastnäsite, indicate that the Nb and REE were transported by the same ore-forming magma or fluid and precipitated during the same metallogenic process. (3) From the fine-grained dolomite stage to the massive mineralization stage (from stage 2 to stage 5), the mineral assemblages become more complex, with a gradual increase in the degree of hydrothermal alteration suggesting that more hydrothermal fluid was involved in the ore mineralization. (4) The complex mineralogical assemblages and textural relationships indicate multiple formation mechanisms for the REE-Nb-Fe minerals. We propose that the unusually large volume of REE-Nb-Fe resources in the Bayan Obo deposit was the result of combined magma and hydrothermal fluid activities in the Mesoproterozoic (from stage 1 to stage 5), whereas the fluids only caused reactivation of the ore materials previously deposited without the addition of exogenous materials in the Paleozoic stage (stage 6). [ABSTRACT FROM AUTHOR]

• Magnetite from fertile intrusion shows magmatic and hydrothermal origin. • Magnetite from barren intrusion is of typical magmatic origin. • The fertile Wenyu pluton formed at higher oxygen fugacity and lower temperature compared to the barren pluton. • Deep sourced was fluid involved in the formation of the Wenyu pluton. The Xiaoqinling district in the southern margin of the North China Craton is the second largest gold enriched area in China. The Huashan and Wenyu plutons represent two typical Mesozoic magmatic intrusions in this region and were coeval with the gold mineralization. Here we report the geochemistry and Mössbauer spectral characteristics of magnetite from the two plutons with a view to explore the role of the granitic magmatism in the gold enrichment. The results of EPMA and Mössbauer spectroscopy suggest that the average values of Fe2+/Fe3+ in the magnetite from the two intrusions are lower than the standard value of 0.50, indicating an oxidizing environment. The estimated oxygen fugacity is higher for the Wenyu pluton than that of the Huashan pluton, which is also supported by the occurrence of hematite in the former, and the distinct δEu-δCe anomalies for magnetite from the two intrusions. The Sn content in magnetite indicates lower formation temperatures of the Wenyu pluton as compared to that of the Huashan pluton. The results of LA-ICP-MS analysis demonstrate similar multi-element variation patterns for the two intrusions. Titanium vs. Ni/Cr relationship suggests that the magnetite from the Huashan pluton is of typical magmatic origin, whereas that from the Wenyu pluton shows both magmatic and hydrothermal signature. The Ni/Co ratio of magnetite from the Wenyu granite is higher than that of the Huashan granite, which indicates a deeper source for the Wenyu pluton. The comparatively more favorable physico-chemical conditions, such as higher oxygen fugacity, lower temperature, as well as the involvement of deep-sourced material are envisaged to have provided better metallogenic environment for generating the gold mineralization around the Wenyu pluton. [ABSTRACT FROM AUTHOR]

• Pyrite Rb-Sr data constrain the timing of gold mineralization as Early Cretaceous. • Zircon U-Pb ages from the clasts do not correspond to the gold metallogeny. • Gold mineralization in extensional setting associated with craton destruction the NCC. The Puziwan gold deposit, located in north-western Shanxi province in North China, is a typical cryptoexplosive breccia-related gold deposit. Here we present new zircon U-Pb and pyrite Rb-Sr geochronology, and zircon Lu-Hf and pyrite S-Pb isotopic data to constrain the timing of ore formation and to gain insights into the source of the metal and genesis of the deposit. The clasts of the ore bodies of the deposit consist mainly of quartz porphyry and granulite. Pyrite and the oxidized limonite account for ∼70% of the total ore minerals associated with the entire ore-forming process. Gold is dominated by electrum and native gold which mainly occur in the interstices and fissures of pyrite. We identify six stages during the mineralization process: (1) gold-bearing quartz-pyrite, (2) quartz-pyrite-sericite, (3) quartz-sericite-Au-Ag polymetallic sulfides, (4) quartz-Ag polymetallic sulfides, (5) gold-bearing sulfide-quartz, and (6) carbonate-pyrite. The pyrite from the main mineralization stage yields Rb-Sr isochron age of 139.2 ± 1.1 Ma, suggesting that the Puziwan gold deposit formed during the Early Cretaceous, much later than the Triassic emplacement of the quartz porphyry (∼229 Ma). The S, Pb and Sr isotopic data suggest that the source of the ore is closely related to deep-seated magmatism derived through mixing of lower crust and mantle material. The geochronological and isotopic data preclude the associated Triassic quartz porphyry as the source, and suggest probable hidden deep-seated Cretaceous magmatism, forming an intrusion related auriferous system. The brecciation resulted from the cryptoexplosion and fluidization. Synchronously, or slightly after the brecciation, the ore fluids were channeled along the breccias and fractures or faults within the fracture zone. Occurrence of other gold deposits in the North China Craton which share similar geochronological and isotopic characteristics with Puziwan gold deposit indicates that these cryptoexplosive breccia-related gold deposits formed during lithospheric extension associated with craton destruction triggered by the subduction of Paleo-Pacific Plate during the Late Jurassic to Early Cretaceous. [ABSTRACT FROM AUTHOR]

The North China Craton (NCC) hosts the world's most typical example of "decratonic" gold deposits including lode, porphyry, cryptoexplosive breccia, and skarn subtypes. The lithospheric structure in the ore fields show "triple-junctions" of basement microblocks, zones of lithospheric thinning, and "hotspots" with abnormal crustal heat flow. The basement rocks are dominantly composed of trondhjemite-tonalite-granodiorite (TTG) suite and amphibolites. The intermediate-felsic calc-alkaline plutons with crust-mantle mixed origin and formed under high oxygen fugacity, volatile-rich and moderately fractionated conditions, together with dyke swarms of diverse compositions are indicators for the gold mineralization. The mantle under the gold field shows metasomatic or juvenile "EM2" or "EM2 + EM1" characteristics. The gold deposits are closely associated with craton destruction, heterogenous reactivation, large-scale magmatic intrusion and eruption, and upwelling of voluminous ore-bearing fluids within a transitional tectonic regime. The presence of mantle-derived mafic rocks, mafic microgranular enclaves (MME) and amygdaloidal bodies, minerals rich in Te, Ni, Cr, Mg, C and N, He and stable isotopes with mantle signature, among other features, indicate that the ore-forming metals and fluids have mixed mantle and deep crustal origin. Gold deposits coexisting or closely associated with mafic dykes and crust-mantle-derived stocks indicate that the upwelling of ore-forming fluid and localization of the ore-materials were facilitated at least partly by the intrusion of deep magma. The spatial distributions of altered rocks with alkali-feldspar-hematite zone distal to the orebody (barren) and pyrite-phyllite (sericite) zone proximal to the ore (ore-bearing zone) indicate a marked physico-chemical interface at the final stage of evolution of the ore-forming fluid. The presence of wide alteration zone indicates that the ore-controlling faults were in a compressive stress state, whereas narrow alteration zone is generally associated with a tensile stress state. The cataclastic, poikilitic, interstitial and zonal textures displayed by the various stages of ore minerals are related to the impact of alternating local tectonic stress fields in the faults, as well as fault-valve mechanism. Intense gold mineralization is typically associated with the development of polymetallic sulfide minerals and complex mineral assemblages. The major gold mineralization is also commonly related with pyrite with xenomorphic or complex forms, rich in As, Se, and Te, with large unit cells, wide X-ray diffraction peaks, and high P/(P + N) values corresponding to thermoelectric conductive type. Quartz grains formed in the main gold mineralization stage are generally fine grained and irregular, occasionally occurring as grain clusters, and showing complex thermoluminescence patterns with both high and low temperature peaks. Multiple rhythmic zones in quartz, pyrite or other ore minerals with various impurities in between the different zones indicate the pulses of ore fluid flow toward the upper part of the orebody. In contrast, minerals with few or no zones may indicate an ore-fluid reservoir typically in the middle to lower parts of orebody. • Indicators of decratonic gold mineralization include geodynamic background and mineralizing processes. • Five subcategories of indicators for geodynamic background are discussed. • Mineralizing processes are indicated by six subcategories of evidences. • Indicators are summarized as references for prospecting similar gold deposits elsewhere. [ABSTRACT FROM AUTHOR]