China National Geological and Mining Corporation

Beijing, China

China National Geological and Mining Corporation

Beijing, China
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Fu Q.,Chinese Academy of Geological Sciences | Fu Q.,Peking University | Xu B.,Chinese Academy of Geological Sciences | Xu B.,China University of Geosciences | And 7 more authors.
Ore Geology Reviews | Year: 2017

Mengya'a is a typical Pb-Zn-(Ag) deposit in the Lhasa terrane, which is located in the eastern part of the central Lhasa subterrane, Tibet. Two different types of Pb-Zn-(Ag) mineralization (skarn and porphyry-like styles) have been identified in the Mengya'a mining district. The skarn-type mineralization occurs as layered or lenticular units in the Laigu Formation and contains nearly all the Pb-Zn ore resources, whereas the porphyry-like mineralization exists mainly as veins in granite porphyry. 40Ar/39Ar dating of muscovite suggests that the skarn orebodies formed at 54.8±0.4Ma, whereas zircon U-Pb dating of granite porphyry (13.2±0.2Ma) indicates that the porphyry-like mineralization formed in the Miocene. As such, the primary mineralization event (skarn type) took place during the main Indo-Asia collision. The ore-forming mineralization and alteration characteristics of the Mengya'a deposit are consistent with other examples of regional Pb-Zn-(Ag) mineralization in the Lhasa terrane. The present results, combined with previous studies, indicate that multiple Pb-Zn-(Ag) mineralization events occurred in the Lhasa terrane, including during the Cretaceous, Paleocene, and Miocene, all of which were associated with felsic intrusions. Sulfur and lead isotopes suggest that the Pb-Zn-(Ag) mineralization events were mainly magmatic in origin, and were closely associated with the ancient basement of the central Lhasa subterrane. Whole rock major and trace elements, and zircon Hf isotope data of the ore-forming intrusions indicate that these intrusions are S-type granites, produced mainly by partial melting of the ancient crust, which underwent extensive fractionation. Therefore, the presence of moderately to strongly fractionated S-types granites, along with the ancient crustal magma source, were the key factors in generating the Pb-Zn-(Ag) mineralization in the central Lhasa subterrane. Crustal melting in the central Lhasa subterrane peaked in the Paleocene, and resulted in the most intense Pb-Zn-(Ag) mineralization during the initial stages of Indo-Asia continental collision (65-50 Ma). During the Cretaceous, the scale of crust melting was considerable, creating large Pb-Zn-(Ag) deposits. Limited Miocene crustal melting and magmatism in the central Lhasa subterrane resulted in the Miocene Pb-Zn-(Ag) mineralization being smaller in scale than that in the Paleocene and Cretaceous. © 2017 Elsevier B.V.

Liang W.,China University of Geoscinces | Liang W.,Chinese Academy of Sciences | Hou Z.,Chinese Academy of Sciences | Yang Z.,Chinese Academy of Geological Sciences | And 5 more authors.
Acta Petrologica Sinica | Year: 2013

Zhaxikang polymetallic base metal deposit is characterized by multiple periods and stages of metallogenesis. Combining the study of regional metaUogenic belt with the feature of typical ore texture and structure, variation of Fe content in sphalerite, the character of elements zonation in lateral and vertical direction, as well as the results of fluid inclusion thermometry, we summarize the remobilization and overprinting metaUlogenesis of Zhaxikang as follows: There had been a coarse-grained sphalerite and galena oreshoot before Tethys Himalaya Sb ( Au) mineralization originated. In post-collisional stage, the crust of Tibet experienced extension and intensity of igneous activity. Geothermal water forming from Meteoric water driven by igneous extracted Sb from stratum around, which formed regional Sb-bearing fluid. The Sb-bearing fluid flowed through Zhaxikang district, and overprinted the former oreshoot which was an effective geochemical barrier. Then the Sb-bearing fluid and replaced coarse-grained galena and sphaerite , from which removed out lead and zinc to form newly mixing fluid. AdditionaUy , this newly formed fluid migrated along NS direction fault system and crystaUized in extension space with form of stockwork , vein and miarolitic type. Zn stiil in forms of sphalerite with Fe content down , and Pb in forms of sulfosalt with Sb and/or Ag. FinaUy , stibnite was to crystaUize as Pb precipitated completely. To sum up , Zhaxikang polymetaUic base metal deposit was a typical but non-unique remobilization and overpriting ore deposit in Tibet Plateau continent to continent coUisional orogenesis and metaUogenesis.

Feng Y.-F.,China University of Geosciences | Deng J.-F.,China University of Geosciences | Xiao Q.-H.,China University of Geosciences | Xing G.-F.,Nanjing Institute of Geology and Mineral Resources | And 7 more authors.
Geology in China | Year: 2011

In this paper the authors conducted zircon U -Pb SHRIMP isotopic dating of the granitic garnet biotite gneiss of the Aojiao Group at Aojiao Village of Dongshan County in Fujian Province. The Th/U ratios in the range of 0.31-1.01 (0.48 on average) show that the zircon is a typical magmatic mineral. The weighted mean 206Pb/238U age is 152.8±1.6 Ma (n=17,MSWD=1.12), which is considered to be the formation age of the gneiss. Some conclusions have been reached; (1)The granitic garnet-biotite gneiss of the Aojiao Group was formed in late Jurassic rather than in pre-Devonian; (2)the Qinyingshan Formation of the Aojiao Group should be divided into metamorphic intrusions and metamorphic sedimentary strata.

Feng Y.-F.,Beijing University of Technology | Deng J.-F.,Beijing University of Technology | Wang S.-J.,Shandong Geological Survey | Xiao Q.-H.,Beijing University of Technology | And 8 more authors.
Geology in China | Year: 2010

Based on 39 SHRIMP and LA-ICP-MS Zircon U-Pb ages, 192 petrochemical data, and two representative age frameworks, this paper suggests a preliminary scheme of the age framework for the early Precambrian granites in western Shandong Province, i.e., three stages of (1)early-middle Neoarchean (2741-2612 Ma), (2)Late Neoarchean (2563-2500 Ma), and (3)early Paleoproterozoic (2494-2435 Ma), which correspond to three rock assemblages and the evolutional trends of (1)T1T2G1 with trondhjemitic trend, (2) T 1T2G1G2QM with both trondhjemitic and cale- alkahne trends, (3)G2QM with cale-alkaline trend. On the basis of both SiO2-MgO and SiO2-FeO/MgO relations, most of T1T2G1 having the magnesian andesitic rock (MA) characteristics is considered to have been formed in the oceanic subduction setting. It is thought that three stages of granitic rock assemblages might have been formed in island-arc, continental marginal arc, and continental collisional settings, respectively, and probably represented the compositions of immature, semi-mature, and mature continental crust, respectively. Thus, the granitic rocks have recorded the process of the formation of the continental crust.

Cao Q.,China University of Geosciences | Cao Q.,China National Geological and Mining Corporation | Liu J.-J.,China University of Geosciences | Li L.-Y.,China National Geological and Mining Corporation | And 4 more authors.
Geology in China | Year: 2015

On the southern margin of the Qinling orogenic belt, there exists a multitude of Early Paleozoic mafic volcanic rocks, and the syenite porphyry veins in the Qiaomaichong gold deposit were intruded in NW direction into mafic volcanic rocks in the study area. By means of studying new zircon LA-ICP-MS U - Pb age and Hf-isotope, whole-rock major and trace elements of syenite porphyry veins in the Qiaomaichong gold deposit and the mafic country rock, the authors tried to constrain the age and petrogenesis and geodynamic background of the siliceous veins. It is revealed that the intrusion of the syenite porphyry can be divided into two phases, and the corresponding two zircon samples of syenite porphyry have 206Pb/238U weighted average ages of (415±7) Ma and (477±6) Ma respectively. The former age belongs to the Late Silurian, whereas the latter to the Early Ordovician. Veins have a high SiO2(>75%) content, σ=1.59, and A/CNK= 1.28, which suggests peraluminous alkaline siliceous shear veins. The εHf (t) values are all positive, and vary in a large range (3.4 to 11.8), which suggests that almost all the matter came from the depleted mantle source, exhibiting a crust-mantle mixing feature. The mafic rocks have a high amount of REE (149.62×l0-6-321.55×l0-6), and are strongly enriched in light rare earth elements, showing a high degree of differentiation. Research shows that this area was within plate tectonic cleavage in the early Paleozoic, so the mantle asthenosphere upwelling of magma formed mafic rocks. Then the veins brought the Au from deep crust into the surface crust in the invasion process, thus providing material of Au sources for preconcentration of Au and later shear mineralization. The determination of the age of the formation of veins has a great significance for the study of late stage gold enrichment.

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