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1.
The Jiehe gold deposit, containing a confirmed gold reserve of 34 tonnes (t), is a Jiaojia-type (disseminated/stockwork-style) gold deposit in Jiaodong Peninsula. Orebodies are hosted in the contact zone between the Jurassic Moshan biotite granite and the Cretaceous Shangzhuang porphyritic granodiorite, and are structurally controlled by the NNE- to NE-striking Wangershan-Hedong Fault. Sulphide minerals are composed predominantly of pyrite with lesser amounts of chalcopyrite, galena, and sphalerite. Hydrothermal alteration is strictly controlled by fracture zones, in which disseminated sulfides and native gold are spatially associated with pervasive sericitic alteration. Mineralogical, textural, and field relationships indicate four stages of alteration and mineralization, including pyrite-bearing milky and massive quartz (stage 1), light-gray granular quartz–pyrite (stage 2), quartz–polysulfide (stage 3) and quartz–carbonate (stage 4) stages. Economic gold is precipitated in stages 2 and 3.The Jiehe deposit was previously considered to form during the Eocene (46.5 ± 2.3 Ma), based on Rb-Sr dating of sericite. However, 40Ar/39Ar dating of sericite in this study yields well-defined, reproducible plateau ages between 118.8 ± 0.7 Ma and 120.7 ± 0.8 Ma. These 40Ar/39Ar ages are consistent with geochronological data from other gold deposits in the region, indicating that all gold deposits in Jiaodong formed in a short-term period around 120 Ma. The giant gold mineralization event has a tight relationship with the extensional tectonic regime, and is a shallow crustal metallogenic response of paleo-Pacific slab subduction and lithospheric destruction in the eastern NCC. 相似文献
2.
The Wangu gold deposit in northeastern Hunan, South China, is one of many structurally controlled gold deposits in the Jiangnan Orogen. The host rocks (slates of the Lengjiaxi Group) are of Neoproterozoic age, but the area is characterized by a number of Late Jurassic–Cretaceous granites and NE-trending faults. The timing of mineralization, tectonic setting and ore genesis of this deposit and many similar deposits in the Jiangnan Orogen are not well understood. The orebodies in the Wangu deposit include quartz veins and altered slates and breccias, and are controlled by WNW-trending faults. The principal ore minerals are arsenopyrite and pyrite, and the major gangue minerals are quartz and calcite. Alteration is developed around the auriferous veins, including silicification, pyritic, arsenopyritic and carbonate alterations. Field work and thin section observations indicate that the hydrothermal processes related to the Wangu gold mineralization can be divided into five stages: 1) quartz, 2) scheelite–quartz, 3) arsenopyrite–pyrite–quartz, 4) poly-sulfides–quartz, and, 5) quartz–calcite. The Lianyunshan S-type granite, which is in an emplacement contact with the NE-trending Changsha-Pingjiang fracture zone, has a zircon LA-ICPMS U–Pb age of 142 ± 2 Ma. The Dayan gold occurrence in the Changsha-Pingjiang fracture zone, which shares similar mineral assemblages with the Wangu deposit, is crosscut by a silicified rock that contains muscovite with a ca. 130 Ma 40Ar–39Ar age. The gold mineralization age of the Wangu deposit is thus confined between 142 Ma and 130 Ma. This age of mineralization suggests that the deposit was formed simultaneously with or subsequently to the development of NE-trending extensional faults, the emplacement of Late Jurassic–Cretaceous granites and the formation of Cretaceous basins filled with red-bed clastic rocks in northeastern Hunan, which forms part of the Basin and Range-like province in South China. EMPA analysis shows that the average As content in arsenopyrite is 28.7 atom %, and the mineralization temperature of the arsenopyrite–pyrite–quartz stage is estimated to be 245 ± 20 °C from arsenopyrite thermometry. The high but variable Au/As molar ratios (>0.02) of pyrite suggest that there are nanoparticles of native Au in the sulfides. An integration of S–Pb–H–O–He–Ar isotope systematics suggests that the ore fluids are mainly metamorphic fluids originated from host rocks, possibly driven by hydraulic potential gradient created by reactivation of the WNW-trending faults initially formed in Paleozoic, with possible involvement of magmatic and mantle components channeled through regional fault networks. The Wangu gold deposit shares many geological and geochemical similarities as well as differences with typical orogenic, epithermal and Carlin-type gold deposits, and may be better classified as an “intracontinental reactivation” type as proposed for many other gold deposits in the Jiangnan Orogen. 相似文献
3.
《Gondwana Research》2014,26(4):1469-1483
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 130–126 Ma Guojialing granite. These deposits collectively formed at ca. 120 ± 5 Ma during rapid uplift of the granite. The Dayingezhuang deposit is a large (> 120 t 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 ± 4 Ma 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. 160–150 Ma Linglong granite–granodiorite massif. The anatectic rocks of the massif were rapidly uplifted, at rates of at least 1 km/m.y. from depths of 25–30 km, 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 126 Ma, 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. 相似文献
4.
Guiqing Xie Jingwen Mao Haijie Zhao Ketao Wei Shangguang Jin Huijun Pan Yufu Ke 《Ore Geology Reviews》2011,43(1):62-77
The Tonglushan ore district in the Middle–Lower Yangtze River Valley metallogenic belt includes the Tonglushan Cu–Fe, the Jiguanzui Au–Cu, and the Taohuazui Au–Cu skarn deposits. They are characterized by NE-striking ore bodies and hosted at the contact of Triassic carbonate rocks and Late Mesozoic granitoid deposits. New Sensitive High-Resolution Ion Microprobe (SHRIMP) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA–ICP-MS) zircon U–Pb, molybdenite Re–Os, and phlogopite 40Ar–39Ar ages indicate that these skarn deposits formed between 140.3 ± 1.1 and 137.3 ± 2.4 Ma. These dates are identical to the zircon U–Pb ages for host quartz diorites ranging from 140 ± 2 to 139 ± 1 Ma. These results confirm that both skarn mineralization and related intrusions were initiated during the Early Cretaceous. The high rhenium contents (261.4–1152 μg/g) of molybdenites indicate that a metasomatic mantle fluid was involved in the ore-forming process of these skarn ore systems. This conclusion is consistent with previously published constraints from sulfur, deuterium, and oxygen isotope compositions, and the geochemical signatures, and Sr–Nd isotopic data of the mineralization-hosting intrusions. Geological and geochronological evidence demonstrates that there were two igneous events in the Tonglushan ore district. The first resulted in the emplacement of quartz diorite during the Early Cretaceous (140 ± 2 to 139 ± 1 Ma), and the second is characterized by the eruption of volcanic rocks during the mid-Early Cretaceous (130 ± 2 to 124 ± 2 Ma). The former is spatially, temporally and genetically associated with skarn gold-bearing mineralization (140.3 ± 1.1 to 137.3 ± 2.4 Ma). The recognition of these two igneous events invalidates previous models that proposed continuous magmatism and associated mineral deposits in the Middle–Lower Yangtze River Valley metallogenic belt. 相似文献
5.
We investigate the Mesozoic–Cenozoic thermal history of the Daxi region (central SE South China Block) to evaluate the influence of the subduction of the Paleo-Pacific oceanic plate beneath the SE South China Block along the block's southeast margin on the tectonothermal evolution of the upper plate. We apply a multi-chronological approach that includes U-Pb geochronology on zircon, 40Ar/39Ar dating on muscovite and biotite from granitic rocks as well as fission-track and (U-Th-Sm)/He analyses on zircon and apatite from granitic and sedimentary rocks. The Heping granite, located in the Daxi region, has a magmatic age of ca. 441 Ma. The biotite 40Ar/39Ar ages of ca. 193 Ma for the Early Jurassic Shibei granite and ca. 160 Ma for the Late Jurassic Fogang granite, respectively, reflect magmatic cooling. The Triassic Longyuanba granite yielded a muscovite 40Ar/39Ar age of ca. 167 Ma, recording heating to ≥ 350 °C induced by nearby intrusion of Middle Jurassic granites. Zircon fission-track and (U-Th-Sm)/He ages from Lower Carboniferous–Lower Jurassic sandstones (140–70 Ma) record continuous cooling during the Cretaceous that followed extensive Middle–Late Jurassic magmatism in the Daxi region. Cretaceous cooling is related to exhumation in an extensional tectonic setting, consistent with lithospheric rebound due to foundering and rollback of the subducted Paleo-Pacific oceanic plate. Apatite fission-track (53–42 Ma) and (U-Th-Sm)/He ages (43–36 Ma), and thermal modelling document rapid cooling in the Paleocene–Eocene, which temporally coincides with continental rifting in the SE South China Block in the leadup to the opening of the South China Sea. 相似文献
6.
The Triassic West Qinling orogen, which formed by the continental collision between the South China block and North China craton following the subduction and closure of the paleo-Tethyan ocean, hosts numerous gold deposits that have commonly considered as products of metamorphic dehydration during the oceanic subduction and subsequent continental collision. However, whether or not there are gold deposits that are genetically related to regional magmatism remains poorly understood. Here we present mineralogical, compositional, and geochronological data of the Dewulu Au-Cu skarn deposit in the Xiahe-Hezuo district to understand the ore genesis and its genetic link to many coeval sediment-hosted disseminated and magmatic-hosted vein gold deposits in the same district, which collectively reveal a possible intrusion-related gold system. The Dewulu Au-Cu skarn deposit in the eastern zone of the Xiahe-Hezuo district is associated with the early Triassic I-type, ilmenite-series Dewulu quartz diorite pluton that intrudes Permian marine clastic and carbonate rocks. Ore-related hydrothermal biotite separates yield a well-defined 40Ar/39Ar plateau age of 239.9 ± 1.4 Ma (2σ), which agrees with a previous zircon U-Pb age (238.6 ± 1.5 Ma at 2σ) of the Dewulu quartz diorite and thus demonstrates a temporal and likely genetic link between the two. Both prograde and retrograde skarn assemblages are well developed in the Dewulu Au-Cu deposit. Prograde garnet and pyroxene are compositionally dominated by grossularite and hedenbergite, respectively, indicating a reduced skarn system. Au-Cu mineralization is largely represented by the arsenopyrite-loellingite-chalcopyrite-pyrrhotite-bornite assemblage and is associated with retrograde skarns. Gold is mostly hosted in arsenopyrite, loellingite and chalcopyrite, and has close textural relations with native bismuth or bismuthides. Mineral stability relationships and fluid inclusion microthermometric data confirm that the prograde skarns formed at a low oxygen fugacity, high temperature (> 630 °C), and a depth range of 2.9 to 6.5 km. Arsenopyrite and chlorite geothermometers indicate that the retrograde skarns and late quartz-sulfide-calcite assemblages formed at 550 to 345 °C and < 350 °C, respectively. The oxygen and sulfur fugacities of ore fluids were below the pyrite-pyrrhotite buffer during the retrograde stage, confirming a reduced fluid system. The reduced nature of ore-forming fluids is inherited from the reduced Dewulu quartz diorite, which was likely caused by significant assimilation of Permian to early Paleozoic carbonaceous and pyritic sedimentary sequences into the parental magmas that originally had a high oxidation state. The Xiahe-Hezuo district also hosts several major sediment-hosted disseminated and magmatic-hosted vein gold deposits, which are broadly coeval with the Dewulu Au-Cu skarn deposit. All those disseminated and vein gold deposits have also been recognized to be genetically related to reduced granitoid intrusions in the Xiahe-Hezuo district. These deposits combined constitute the first intrusion-related gold system in the West Qinling orogen. 相似文献
7.
The southern North China craton hosts numerous world-class porphyry Mo and Pb-Zn-Ag vein deposits. Whether or not the Pb-Zn-Ag veins are genetically associated with the porphyry Mo system remains contentious. Here we focus on the genetic relationships between the Sanyuangou Pb-Zn-Ag vein deposit and the world-class Donggou porphyry Mo deposit, and discuss the potential implications from the spatial and temporal relationships between porphyry and vein systems in the southern North China craton.At Sanyuangou, vein-hosted sulfide mineralization mainly comprises pyrite, sphalerite, and galena, with minor chalcopyrite, pyrrhotite, bornite, tetrahedrite, covellite, polybasite and argentite. The mineralization is hosted by a quartz diorite stock, which has a zircon U-Pb age of 1756 ± 9 Ma. However, sericite from alteration selvages of Pb-Zn-Ag sulfide mineralization yields a well-defined 40Ar/39Ar plateau age of 115.9 ± 0.9 Ma. Although nominally younger, the sericite 40Ar/39Ar age is similar to the age of the nearby Donggou porphyry Mo deposit (zircon U-Pb age of 117.8 ± 0.9; molybdenite Re-Os ages of 117.5 ± 0.8 Ma and 116.4 ± 0.6 Ma). Pyrite from Donggou has elevated contents of Mo and Bi, whereas pyrite from Sanyuangou is enriched in Cu, Zn, Pb, Ag, Au, and As. This trace element pattern is consistent with metal zonation typically observed in porphyry related metallogenic systems. Pyrite grains from Sanyuangou have lead isotopes overlapping those from Donggou (17.273–17.495 vs. 17.328–17.517 for 206Pb/204Pb, 15.431–15.566 vs. 15.408–15.551 for 207Pb/204Pb, and 37.991–38.337 vs. 38.080–38.436 for 208Pb/204Pb). Collectively, the geological, geochronological, and geochemical data support a magmatic-hydrothermal origin for the Sanyuangou Pb-Zn-Ag deposit and confirm that the Pb-Zn-Ag veins and the Donggou Mo deposit form a porphyry-related magmatic-hydrothermal system.Given the widespread Pb-Zn-Ag veins and Mo mineralized porphyries in many districts of the southern North China craton, the model derived from this study has broad implications for further exploration of Mo and Pb-Zn-Ag resources in the area. 相似文献
8.
The large Huamei'ao tungsten deposit, with total WO3 reserves of 67,400 tons at an average grade of 1.334% WO3, is located in the convergent zone of the eastern Nanling E–W-trending tectono-magmatic belt and the western Wuyishan NNE–SSW-trending tectono-magmatic belt in southern Jiangxi Province, China. The tungsten mineralization in this deposit is mainly found in quartz–wolframite veins, with most orebodies distributed at the outer contact zone between concealed Late Jurassic granitic stocks and Sinian weakly metamorphosed sandstones and phyllites. Zircons collected from medium- to fine-grained biotite granite in a diamond drill hole at a sea level of ca. − 10 m yield a crystallization age of 159.9 (± 1.2) Ma through laser ablation–multicollector–inductively coupled plasma–mass spectrometry (LA–MC–ICP–MS) U–Pb dating. Molybdenite and muscovite that were both separated from quartz–wolframite veins yield a Re–Os isochron age of 158.5 (± 3.3) Ma and an 40Ar–39Ar weighted plateau age of 157.9 (± 1.1) Ma, respectively. These dates, obtained via three independent geochronological techniques, constrain the ore-forming age of the Huamei'ao deposit and link the genesis of the ore and the underlying granite. Analyses of available high-precision zircon U–Pb, molybdenite Re–Os and muscovite 40Ar–39Ar radiometric ages of major W–Sn deposits in southern Jiangxi Province indicate that there is no significant time interval between W–Sn mineralization and its intimately associated parent granite emplacement (interval of 0–6 Ma). These deposits formed over three intervals during the Mesozoic (240–210, 170–150, and 130–90 Ma), with large-scale W–Sn mineralization occurring mainly between 160 and 150 Ma. The majority of W–Sn deposits in this region are located in southern Jiangxi and southern Hunan provinces. 相似文献
9.
《Journal of African Earth Sciences》2008,50(2-4):204-214
The Tamlalt–Menhouhou gold deposit belongs to the Neoproterozoic–Palaeozoic Tamlalt inlier located in the Eastern High-Atlas (Morocco). It occurs in altered Upper Neoproterozoic bimodal volcanic and volcano-sedimentary units outcropping in the Tamlalt–Menhouhou area. Gold mineralization has been identified in quartz veins related to shear-zones associated with a strong quartz-phyllic-argillic alteration. Visible free gold is related to goethite–malachite–barite boxworks in quartz veins. The other alteration minerals accompanying gold mineralization are mainly carbonates, chlorite, hematite, albite and pyrite whose relative proportion defines three alteration types. 40Ar/39Ar geochronology performed on phengite grains from phyllic alteration and the auriferous quartz veins, yields plateau ages ranging from 300 ± 5 Ma to 284 ± 12 Ma with a weighted mean age of 293 ± 7 Ma. This identifies a Late Variscan age for the Tamlalt–Menhouhou “shear zones-related” gold deposit and emphasizes the consequences of the Variscan orogeny for gold mineralization in the High-Atlas and Anti-Atlas Neoproterozoic inliers. 相似文献
10.
Blueschists are sporadically exposed as lenses within the Lancangjiang metamorphic complex, and represent unique components of the Paleo-Tethys. In this paper, we present geochemical and geochronological results of blueschists to decipher their origin and tectonic significance. The whole-rock geochemical analyses revealed strong similarities with ocean island basalt (OIB), and further discrimination diagrams confirm an affinity to a within-plate setting. Combined studies on blueschists using cathodoluminescence (CL) imaging, SHRIMP U-Pb dating of zircon domains and 40Ar/39Ar dating of phengite and glaucophane provide evidence of their magmatic origin and metamorphic evolution. Slightly oscillatory zoned or compositionally homogeneous zircon grains/domains, as well as structureless zircon rims, yield ages from 231.6 ± 3.7 to 225.3 ± 4.8 Ma, recording the blueschist facies metamorphic event. In contrast, the captured zircon grains and cores with a major age peak at ~241 Ma as well as several minor older age peaks indicate the multiple provenance of the zircons. 40Ar/39Ar step heating analyses on single grains of phengite and glaucophane separated from blueschists yield plateau ages ranging from 242.5 ± 1.4 to 228.7 ± 1.5 Ma which are interpreted to reflect high-pressure metamorphism.This study provides geochemical and geochronological constraints on the tectonic evolution of the Paleo-Tethyan ocean, which was closed and subsequently subducted as a result of the collision of the Simao and Baoshan Blocks. During subduction in Trassic (243 to 225 Ma), the protoliths of blueschists underwent blueschist facies conditions. 相似文献
11.
The Laowan metallogenic belt in China is an important metallogenic belt within the Tongbai orogenic belt, and contains the medium-sized Laowan and Shangshanghe gold deposits, the small Huangzhuyuan lead–zinc–silver–gold deposit and some gold and Cu–Pb occurrences. These deposits are hosted in Mesoproterozoic plagioclase amphibolite (or schist) and mica-quartz schist. The gold ores are mainly quartz veins and veinlets and disseminated altered ores. Subordinate ore types include massive sulfides and breccias. The Laowan gold deposit is characterized by three right-stepping en-echelon fracture-controlled alteration zones that dip gently to the south and includes disseminated, sheeted and stockwork ores. These lodes were formed by the interaction of ore-forming fluid with foliated-to laminated cataclasite within the transpressional faults. The Shangshanghe gold deposit is characterized by parallel ore lodes that dip steeply to the north, and includes quartz veins and breccias in addition to ores in altered wallrocks. These lodes were formed by focusing of fluids into transtensional faults. These ore controlling faults displaced early barren quartz veins 10 m horizontally with a dextral sense of motion. The ore-hosting structures at the Laowan and Shangshanghe deposits correspond to the P and R-type shears of a brittle dextral strike-slip fault system, respectively, which make angles of about 15° and − 15° to the Laowan and Songpa boundary faults. The ore-controlling fault system post-dated formation of a ductile shear zone, and peak regional metamorphism. This precludes a genetic relationship between hydrothermal mineralization and regional metamorphism and ductile shear deformation. These gold deposits are not typical orogenic gold deposits. The metallogenic belt displays district-scale-zoning of Mo → Cu–Pb–Zn–Ag → Au relative to Songpa granite porphyry dike zone, suggesting the mineralization may be closely related to the granite porphyry. Measured δ34S of sulfides and δ18O and δD of fluid inclusion waters in auriferous quartz also are consistent with a magmatic source for sulfur and ore fluids. The similarity of Pb isotope ratios between the ores and Yanshanian granitoids suggests a similar source. As the age (139 ± 3 Ma) of granite porphyry obtained by zircon U–Pb isotope overlaps the mineralization age (138 ± 1 Ma: Zhang et al., 2008a), the gold and polymetallic metallogenesis of the Laowan gold belt has close spatial, temporal and possibly genetic relationships with Yanshanian high level magmatism. 相似文献
12.
The genesis of polymetallic deposits in southern Altay, NW China has been disputed between a syngenetic seafloor hydrothermal process and an epigenetic orogenic-type mineralization. The Dadonggou Pb–Zn deposit occurs as NW-trending veins in the Devonian Kangbutiebao Formation volcanic-sedimentary sequence in the Kelan basin, southern Altay. A set of integrated zircon U–Pb and biotite 40Ar/39Ar geochronological data were applied to constrain the forming ages of the ores and their country rocks. Three samples of host volcanic rocks yielded weighted mean 206Pb/238U ages of 397.1 ± 4.5 Ma, 391.7 ± 3.6 Ma and 391.1 ± 4.2 Ma, respectively, indicating that the Kangbutiebao Formation was deposited in a Devonian back-arc basin. Two biotite samples separated from the Pb–Zn-containing quartz veins yielded 40Ar/39Ar plateau ages of 205.9 ± 2.1 Ma and 204.3 ± 2.2 Ma, respectively, which represent the age of the Pb–Zn mineralization that is attributed to the closure of the Kelan back-arc basin and the Late Triassic orogeny. Combining the available geological and geochronological data, this contribution outlines the successive evolution from the development of a Devonian back-arc basin to the Late Triassic post-subduction orogeny, and proposes that the Dadonggou Pb–Zn deposit is an epigenetic orogenic-type deposit placed in the Late Triassic orogeny. 相似文献
13.
The Fujiawu porphyry Cu–Mo deposit is one of several porphyry Cu–Mo deposits in the Dexing district, Jiangxi Province, Southeast China. New zircon SHRIMP U–Pb data yield a weighted mean 206Pb/238U age of 172.0 ± 2.1 and 168.5 ± 1.4 Ma from weakly altered granodiorite porphyry and quartz diorite porphyry, respectively. Two hydrothermal biotites from granodiorite porphyry give an Ar–Ar step-heating plateau age of 169.9 ± 1.8 and 168.7 ± 1.8 Ma. Hydrothermal apatite exsolved from altered biotite yields an isotope dilution thermal ionization mass spectrometry isochron age of 164.4 ± 0.9 Ma. The apatite age is similar to the ages obtained from hydrothermal rutile (165.0 ± 1.1 and 164.8 ± 1.6 Ma) and indicates that the magmatism and hydrothermal activity in the Fujiawu deposit occurred in the Middle Jurassic. Hydrothermal fluid circulation related to multiple stages of magma emplacement resulted in Cu–Mo mineralization in the Fujiawu porphyry deposit. The zircon SHRIMP U–Pb ages and the published molybdenite Re–Os age (170.9 ± 1.5 Ma) represent the timing of magma crystallization and Mo mineralization, whereas the rutile and apatite U–Pb ages reflect the timing of Cu mineralization following quartz diorite emplacement. The data suggest slow cooling after emplacement of the quartz diorite porphyry. 相似文献
14.
Lai-min Zhu Guo-wei Zhang Yan-jing Chen Zhen-ju Ding Bo Guo Fei Wang Ben Lee 《Ore Geology Reviews》2011,39(1-2):46-62
East Qinling is the largest porphyry molybdenum province in the world; these Mo deposits have been well documented. In West Qinling, however, few Mo deposits have been discovered although granitic rocks are widespread. Recently, the Wenquan porphyry Mo deposit has been discovered in Gansu province, which provides an insight into Mo mineralization in West Qinling. In this paper we report Pb isotope compositions for K-feldspar and sulfides, S isotope ratios for sulfides, the results obtained from petrochemical study and from in situ LA-ICP-MS zircon U-Pb dating and Hf isotopes. The granitoids are enriched in LILE and LREE, with REE and trace element patterns similar to continental crust, suggesting a crustal origin. The Mg# (40.05 to 56.34) and Cr and Ni contents are high, indicating a source of refractory mafic lower crust. The εHf(t) values of zircon grains from porphyritic monzogranite range from ? 2.9 to 0.6, and from granitic porphyry vary from ? 3.3 to 1.9. The zircons have TDM2 of 1014 to 1196 Ma for the porphyritic monzogranite and 954 to 1224 Ma for the granitic porphyry, implying that these granitoids were likely derived from partial melting of a Late Mesoproterozoic juvenile lower crust. The Pb isotope compositions of the granitoids are similar to granites in South China, showing that the magma was sourced from the middle–lower crust in the southern Qinling tectonic unit. The Pb isotopic contrast between the Mo-bearing granitoids and ores shows that the Pb in the ore-forming solution was derived from fractionation of a Triassic magmatic system. δ34S values of sulfides are between 5.02 and 5.66‰, similar to those associated with magmatic-hydrothermal systems. LA-ICP-MS zircon U-Pb dating yields crystallization ages of 216.2 ± 1.7 and 217.2 ± 2.0 Ma for the granitoids, consistent with a previously reported molybdenite Re-Os isochron age of 214.4 ± 7.1 Ma. This suggests that the Mo mineralization is related to the late Triassic magmatism in the West Qinling orogenic belt. In view of these geochemical results and known regional geology, we propose that both granitoid emplacement and Mo mineralization in the Wenquan deposit resulted from the Triassic collision between the South Qinling and the South China Block, along the Mianlue suture. Since Triassic granitoid plutons commonly occur along the Qinling orogenic belt, the Triassic Wenquan Mo-bearing granitoids highlight the importance of the Triassic tectono-magmatic belt for Mo exploration. In order to apply this metallogenic model to the whole Qinling orogen, further study is needed to compare the Wenquan deposit with other deposits. 相似文献
15.
The Tongjing Cu–Au deposit is a medium-sized deposit within the Ningwu volcanic basin, east China, and is hosted by Cretaceous volcanic rocks of the Dawangshan and Niangniangshan Formations. The veined and lenticular Cu–Au orebodies are spatially and temporally related to the volcanic and subvolcanic rocks of the Niangniangshan Formation in the ore district. The wall-rock alteration is dominated by silicification, siderite alteration, carbonation, sericitization, chloritization, and kaolinization. On the basis of field evidence and petrographic observations, two stages of mineralization are recognized: (1) a siderite–quartz–sulfide stage (Stage 1) associated with the formation of chalcopyrite and pyrite in a quartz and siderite gangue; and (2) a quartz–bornite stage (Stage 2) cutting the Stage 1 phases. Stage 1 is the main mineralization stage. Quartz that formed in Stage 1 has δ18OH2O values of − 4.3‰ to 3.5‰ with δD values of fluid inclusion waters of − 97.1‰ to − 49.9‰, indicating that the ore-forming fluids were derived from early magmatic fluids and may have experienced oxygen isotopic exchange with meteoric water during Stage 1 mineralization.LA–MC–ICP–MS zircon U–Pb dating of the mineralization-related nosean-bearing phonolite and nosean-bearing phonolitic brecciated tuff at Tongjing yields ages of 129.8 ± 0.5 Ma and 128.9 ± 1.1 Ma, respectively. These results are interpreted as the crystallization age of the volcanic rocks of the Niangniangshan Formation. A hydrothermal sericite sample associated with Cu–Au mineralization at Tongjing yields a plateau 40Ar–39Ar age of 131.3 ± 1.3 Ma. These results confirm a genetic link between the volcanism and associated Cu–Au mineralization. The Tongjing Cu–Au deposit in the Ningwu basin is genetically and possibly tectonically similar to alkaline intrusion-related gold deposits elsewhere in the world. 相似文献
16.
Cenozoic lamprophyre dykes occur widely along the Ailao-Shan-Red-River (ASRR) shear zone related to the Indian–Eurasian collision. Two generations of lamprophyres have been found at the Daping gold deposit in the southern part of the ASRR shear zone and have been investigated by using phlogopite 40Ar/39Ar dating and whole-rock major and trace element as well as Sr and Nd isotope geochemical analyses. The 40Ar/39Ar plateau ages of phlogopite from the two generations of lamprophyres bracket the emplacement of auriferous quartz veins in the Daping deposit between 36.8 ± 0.2 Ma and 29.6 ± 0.2 Ma, consistent with the timing of gold mineralization in other parts of the ASRR shear zone. Geochemical data suggest that these lamprophyres most likely originated from a subduction-modified mantle source consisting of phlogopite-bearing spinel lherzolite, which underwent partial melting with contributions from crust materials. In particular, the second generation lamprophyres are characterized by more primitive geochemical features than the first, suggesting that secular source evolution probably resulted from post-collisional slab break-off mantle convection and remelting from ascending asthenosphere after subducted lithosphere break-off. Widespread and episodic occurrences of lamprophyres and other potassic volcanism in the eastern Tibetan Plateau were probably related to the onset of transtensional tectonics along the ASRR shear zone during Oligocene. A genetic model involving transtensional tectonics has been proposed for lamprophyres and gold mineralization in the ASRR shear zone. 相似文献
17.
The Balkhash Metallogenic Belt (BMB) in Kazakhstan, Central Asia, with the occurrence of the super-large Kounrad and Aktogai, the large Borly porphyry Cu–Mo deposits, and the large Sayak skarn polymetallic ore-field, is one of the central regions of the Paleozoic Central Asian metallogenic domain and orogenic belt. In this study, newly obtained SHRIMP zircon U–Pb ages of nine samples and 40Ar/39Ar ages of six mineral samples (inclding hornblende, biotite and K-feldspar) give more detailed constraints on the timing of the granitic intrusions and their metallogeny. Porphyritic monzonite granite and tonalite porphyry from the Kounrad deposit yield U–Pb zircon SHRIMP ages of 327.3 ± 2.1 Ma and 308.7 ± 2.2 Ma, respectively. Quartz diorite and porphyritic granodiorite from the Aktogai deposit yield U–Pb SHRIMP ages of 335.7 ± 1.3 Ma and 327.5 ± 1.9 Ma, respectively. Porphyritic granodiorite and granodiorite from the Borly deposit yield U–Pb SHRIMP ages of 316.3 ± 0.8 Ma and 305 ± 3 Ma, respectively. Diorite, granodiorite, and monzonite from the Sayak ore-field yield U–Pb SHRIMP ages of 335 ± 2 Ma, 308 ± 10 Ma, and 297 ± 3 Ma, respectively. Hornblende, biotite, and K-feldspar from the Aktogai deposit yield 40Ar/39Ar cooling ages of 310.6 Ma, 271.5 Ma, and 274.9 Ma, respectively. Hornblende, biotite, and K-feldspar from the Sayak ore-field yield 40Ar/39Ar cooling ages of 287.3 ± 2.8 Ma, 307.9 ± 1.8 Ma, and 249.8 ± 1.6 Ma, respectively. The new ages constrain the timing of Late Paleozoic felsic magmatism to ∼336 to ∼297 Ma. Skarn mineralization in the Sayak ore-field formed at ∼335 and ∼308 Ma. Porphyry Cu–Mo mineralization in the Kounrad deposit and the Aktogai deposit formed at ∼327 Ma, and in the Borly deposit at ∼316 Ma. The Late Paleozoic regional cooling in the temperature range of ∼600 °C to ∼150 °C occurred from ∼307 to ∼257 Ma. 相似文献
18.
The junction of the southeastern Guizhou, the southwestern Hunan, and the northern Guangxi regions is located within the southwestern Jiangnan orogen and forms a NE-trending ∼250 km gold belt containing more than 100 gold deposits and occurrences. The Pingqiu gold deposit is one of the numerous lode gold deposits in the southeastern Guizhou district. Gold mineralization is hosted in Neoproterozoic lower greenschist facies metamorphic rocks and controlled by fold-related structures. Vein types present at Pingqiu include bedding-parallel and discordant types, with saddle-reefs and their down limb extensions dominating but with lesser discordant types. The major sulfide minerals are arsenopyrite and pyrite, with minor sphalerite, galena, chalcopyrite, and rare pyrrhotite, marcasite, and tetrahedrite. Much of the gold is μm- to mm-sized grains, and occurs as fracture-controlled isolated grains or filaments in quartz, galena, sphalerite, pyrite, and wallrock.Three types of fluid inclusions are distinguished in hydrothermal minerals. Type 1 aqueous inclusions have homogenization temperatures of 171–396 °C and salinities of 1.4–9.8 wt% NaCl equiv. Type 2 aqueous-carbonic inclusions yield final homogenization temperatures of 187–350 °C, with salinities of 0.2–7.7 wt% NaCl equiv. Type 3 inclusions are carbonic inclusions with variable relative content of CO2 and CH4, and minor amounts of N2 and H2O. The close association of CO2-rich inclusions and H2O-rich inclusions in groups and along the same trail suggests the presence of fluid immiscibility. The calculated δ18OH2O values range from 4.3‰ to 8.3‰ and δDH2O values of fluid inclusions vary from −55.8‰ to −46.9‰. A metamorphic origin is preferred on the basis of geological background and analogies with other similar deposit types.Two ore-related sericite samples yield well-defined 40Ar/39Ar plateau ages of 425.7 ± 1.7 Ma and 425.2 ± 1.3 Ma, respectively. These data overlap the duration of the Caledonian gold mineralization along the Jiangnan orogen, and suggest that gold mineralization was post-peak regional metamorphism and occurred during the later stages of the Caledonian orogeny.Overall, the Pingqiu gold deposit displays many of the principal characteristics of the Bendigo gold mines in the western Lachlan Orogen (SE Australia) and the Dufferin gold deposit in the Meguma Terrane (Nova Scotia, Canada) but also some important differences, which may lead to the disparity in gold endowment. However, the structural make-up at deposit scale, and the shallow mining depth at present indicate that the Pingqiu gold deposit may have considerable gold potential at depth. 相似文献
19.
The Hukeng tungsten deposit, located in the Wugongshan area in central part of Jiangxi province, South China, is a large-scale quartz-vein wolframite deposit. It is hosted in the Hukeng granitic intrusion. Based on the mineral assemblage and crosscutting relationship of the veins, three mineralization stages are identified, including: (1) quartz–wolframite stage, (2) quartz–fluorite–wolframite stage, and (3) quartz–pyrite–sphalerite–wolframite stage.The homogenization temperatures of fluid inclusions in vein quartz vary from 220 to 320 °C, and the salinities are from 0 to 10 wt.% NaCl equiv.; corresponding densities range from 0.7 to 1 g/cm3. These features indicated that the ore-forming fluids in the Hukeng tungsten deposit have medium temperature, low density and low salinity.The δ18OSMOW values of quartz range from 10.8‰ to 14.4‰, with corresponding δ18Ofluid values of 3.7‰ to 7.7‰, and δD values of fluid inclusions of between ? 70‰ and ? 55‰. The combined isotopic data indicate that the ore-forming fluids of the Hukeng tungsten deposit were mainly derived from magmatic water, with some minor input from meteoric water.We have carried out molybdenite Re–Os and muscovite 40Ar/39Ar dating to constrain the timing of mineralization. Re–Os dating of six molybdenite samples yielded model ages ranging from 149.1 ± 2.0 to 150.7 ± 3.7 Ma, with an average of 150.0 Ma. The Re–Os analyses give a well-defined 187Re/187Os isochron with an age of 150.2 ± 2.2 Ma (MSWD = 0.60). Hydrothermal muscovite yields a plateau 40Ar/39Ar age of 147.2 ± 1.4 Ma. 40Ar/39Ar age is in good agreement with the Re–Os age. These ages show that the timing of tungsten mineralization occurred at about 150 Ma. Our new data, when combined with published geochronological results from the other major deposits in this region, suggest that widespread W mineralization occurred in the Late Jurassic throughout South China. 相似文献
20.
A 2000 km long dextral Talas-Fergana strike–slip fault separates eastern terranes in the Kyrgyz Tien Shan from western terranes. The aim of this study was to constrain an age of dextral shearing in the central part of the fault utilizing Ar–Ar dating of micas. We also carried out a U–Pb–Hf zircon study of two different deformed granitoid complexes in the fault zone from which the micas for Ar dating were separated. Two samples of the oldest deformed Neoproterozoic granitoids in the area of study yielded U–Pb zircon SHRIMP ages 728 ± 11 Ma and 778 ± 11 Ma, characteristic for the Cryogenian Bolshoi Naryn Formation, and zircon grains analyzed for their Lu–Hf isotopic compositions yielded εHf(t) values from −11.43 to −16.73, and their calculated tHfc ages varied from 2.42 to 2.71 Ga. Thus varying Cryogenian ages and noticeable heterogeneity of Meso- to Paleoproterozoic crustal sources was established for mylonitic granites of the Bolshoi Naryn Formation. Two samples of mylonitized pegmatoidal granites of the Kyrgysh Complex yielded identical 206Pb/238U ages of 279 ± 5 Ma corresponding to the main peak of Late-Paleozoic post-collisional magmatism in the Tien Shan (Seltmann et al., 2011), and zircon grains analyzed for their Lu–Hf isotopic compositions yielded εHf(t) values from −11.43 to −16.73, and calculated tHfc ages from 2.42 to 2.71 Ga indicating derivation from a Paleoproterozoic crustal source. Microstructural studies showed that ductile/brittle deformation of pegmatoidal granites of the Kyrgysh Complex occurred at temperatures of 300–400 °C and caused resetting of the K–Ar isotope system of primary muscovite. Deformation of mylonitized granites of the Bolshoi Naryn Formation occurred under high temperature conditions and resulted in protracted growth and recrystallization of micas. The oldest Ar–Ar muscovite age of 241 Ma with a well defined plateau from a pegmatoidal granite of the Kyrgysh Complex is considered as a “minimum” age of dextral motions along this section of the fault in the Triassic while younger ages varying from 227 Ma to 199 Ma with typical staircase patterns indicate protracted growth and recrystallization of micas during ductile deformations which continued until the end of the Triassic. 相似文献