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Li Y.,China University of Geoscinces | Li Y.,Shillazhuang University of Economics | Wang J.,Shillazhuang University of Economics | Li H.,Shillazhuang University of Economics | Dong P.,Shillazhuang University of Economics
Yanshi Xuebao/Acta Petrologica Sinica | Year: 2015

Firstly recognized Meilaotewula ophiolite occurs in Xing' anling-Mongolian Orogenic Belt (XMOB) between the Sino- Korean Paleoplate and the Siberian Paleoplate in the central sector of Inner Mongolia. Based on the regional geology, the Meilaotewula ophiolite can be the eastward extension of the Erlianhaote-Hegenshan ophiolite zone. According to field geological investigation and the preliminary results of petrology and geochemistry, we found Meilaotewula ophiolite is about 6 ~ 11km wide, and extends 24km in a ENE-NE direction , and it outcrops completely , including augite peridotite , beded-massive gabbro , diabase , piilow basalt , augitophyre , and chert. The augite peridotites are characterized by low SiO2 , high MgO , U-shaped chondrite-normalized REE patterns , represent a typical mantle section of the supra-subduction zone ( SSZ) setting. Piilow basalts and diabase are characterized by low K2 of ( average 0. 82% ) and TiO2 (0. 8% ~ 1. 2% ) , and have flat to slightly LREE-depleted chondrite-normalized REE patterns. In MORB- normalized spider diagrams , piilow basalts and diabase are enriched in Sr , K , Rb and Ba , and depleted in Nb , Th , Ta , Zr and Ti , displaying the Unity of the supra-subduction zone (SSZ) setting. LA-ICP-MS U-Pb dates on zircon of massive gabbro yield ages of 308.5 ± 2. 2Ma , which is the crystallizatioan age of gabbro , indicating a Late Carboniferous age of Meilaotewula ophiolite. All the research results above provide important evidence in exploring the tectonic evolution of Xing' anling-Mongolian Orogenic Belt (XMOB).

Shen Z.,Chinese Academy of Geological Sciences | Shen Z.,China University of Geoscinces | Hou Z.,Chinese Academy of Geological Sciences | Yu F.,China University of Geoscinces | And 5 more authors.
Acta Petrologica Sinica | Year: 2015

The geochronologucal and geochemical data of the Mesozoic intermediate-acidic rocks from the northern Taihang Mountains provide an insight into the understanding of the nature of the Mesozoic lithospheric mantle beneath the North China interior. The Tiaojishan Formation volcanic-andesite, granodiorite, and monzonitic granite, the representative for the Wanganzhen complex, yield the SHRIMP zircon U-Pb ages of 138. 89 ±0. 9Ma , 135. 7 ± 1. 3Ma , and 133. 7 ± 1. 1Ma , respectively. The ages are consistent with the mafic rocks (138Ma) of Wanganzhen complex. The granodiorites have values of -21. 81 16. 09, corresponding to tM model ages of 2. 2 ∼2. 6Ga; the monzonitic granites have £Hf (t) values of - 20. 50 ∼ -16.31, corresponding to tDMC model ages of 2. 2 ∼ 2. 5Ga, which are rather similar with those of mafic rocks with εHf(t) values of -22.8 ∼ -15.3. The origin of the intermediate-acidic rocks could be summarized as folows: The basaltic melts originated from the melting of an enriched subcontinental lithospheric mantle ( EMI) beneath the North China Craton underwent lower crustal contamination and subsequent fractional crystallisation during their ascent, which is crucial for the origin of the intermediate-acidic rocks in Wanganzhen complex. Mesozoic lithospheric extension might induce the melting of the enriched lithospheric mantle in response to the asthenosphere uprising for generating these intermediate-acidic rocks in the region.

Cao Y.,China University of Geoscinces | Du Y.,China University of Geoscinces | Pang Z.,Development and Research Center | Ren C.,China University of Geoscinces | And 4 more authors.
Yanshi Xuebao/Acta Petrologica Sinica | Year: 2016

The Dongguashan copper (gold) deposit is located in the Tongling copper-gold ore district of the Middle-Lower Yangtze River metallogenic belt. It is one of the most important and reprehensive deposits in this district and gets popular concerned since it has been discovered with hotly debated about the genesis. The massive sulfide ore generally develop sulfide zonal texture with pyrite as nuclear, chalcopyrite as intermediate zone and pyrrhotite as outer zone. Pyrite in the core is usually euhedral or subhedral crystal while the coating chalcopyrite and pyrrhotite are anhedral. Chalcopyrite precipitate around the early-formed pyrite, pyrrhotite which acted as the mainbody of the sulfide zonal texture grows around the chalcopyrite. The inner sulfide is generally replaced by the outer one. These suggest that the sulfide zonal texture formed from the inside to the outside as the following order: pyrite-chalcopyrite-pyrrhotite. The δ34S of sulfides have a magmatic feature ranging from 1.6‰ to 5.1‰, and an order as δ34SPo < δ34SSCcp < δ34SPy, indicating that the sulfur fractionation had not reached a thermodynamic equilibrium. The Co and Ni content of coarse-grained pyrite (> 1.5cm) are 292 × 10-6 ∼ 1504 × 10-6 and 32.7 × 10-6 ∼ 39. 9 × 10-6, respectively, which is consistent with the Co and Ni content of Sedex pyrite. The Fe/S atomic ratio and the content of Mo and Co increase gradually at first, and then decreased from core to rim of pyrite. Ore-forming elements (e. g., Cu, Zn) mainly enriched in pyrite rim, and their concentrations increase from inside to outside of pyrite rim. Furthermore, ore-forming elements content in fine-grained pyrite (<0.5cm) are significantly higher than those in coarse-grained pyrite (> 1.5cm). These features, together with field and microscopic investigation, suggest that the pyrite in the core probably underwent metamorphism and hydrothermal replacement. Analysis of trace elements exhibit similar characteristics from different sulfides of the zonal texture, for example, riehen in LREE, Rb and Th, and depleted in Nb, Ta, Zr, Hf, Sr, Ba and HREE. Both the REEs and incompatible elements distribution patterns of sulfides are similar to those of quartz monzodiorite in Dongguashan area. Based on the information discussed above, a model for the formation of the zonal sulfides in the Dongguashan deposit can be established. The model can be described as follows : during the Middle Carboniferous period, submarine exhalation sedimentation caused the formation of sedimentary pyrite which shows colloidal and concentric textures; during the Yanshanian, the heat from quartz monzodiorite has resulted in metamorphic recystallization of sedimentary pyrite, and formed the granular pyrite ; and subsequent magmatic hydrothermal fluids superimposition lead to sulfide gradually precipitate as the order of pyrite-chalcopyrite-pyrrhotite around the early-formed pyrite, and formed sulfide zonal texture with pyrite as nuclear, chalcopyrite as intermediate zone and pyrrhotite as outer zone. This conclusion, combination with element and sulfide isotope data, supports the submarine exhalation sedimentation-magmaitic hydrothermal reformation model for the Dongguashan ore deposit, and further suggest that most of economic metals (e. g., Cu, Zn) were introduced through hydrothermal fluids during emplacement of the Yanshanian quartz monzodiorite, whereas small part of metals (e. g., Fe, S, Mo, Co and Ni) were derived from the Middle Carboniferous submarine exhalation sedimentation. Additionally, from nuclear pyrite to intermediate chalcopyrite and to outer pyrrhotite, δEu and Co/Ni ratio show gradually decreasing pattern, indicating that decreasing of temperature, fs2 and fo2 and/or arising pH value of mineralizing fluid from the earlier to later.

Zhang L.T.,China University of Geoscinces | Yuan W.M.,China University of Geoscinces | Li N.,China Guanghua Foundation | Huan W.J.,China Railway Resources Group Co. | And 3 more authors.
Acta Petrologica Sinica | Year: 2015

Ganzi-Litang gold belt belongs to the Sanjiang Tethyan orogenic belt and it is a typical representative of gold mineralization. The Ganzi-Litang fault has experienced multiple tectonic activities that are conducive to the gold element migration and favorable for mineralization. In this paper, a total of five typical deposits, Cuo'a, Xichongnong, Gala, Xionglongxi and Qukailongwa, were introduced. The nine apatite fission track ages are achieved and show four groups of 92 ∼ 88Ma, 34 ∼ 26Ma, 17 ∼ 15Ma and 8. 1Ma. According to the sample result, the uplift amplitude and the uplift rate are calculated quantatively, revealing different orders of magnitude and the uneven uplift. The uplift amplitude is divided into three orders of magnitude, which is 5405m, 6023 ∼ 6272m and 6519 ∼6576m. The uplift rate is divided into four orders of magnitude, which is 0.07mm/a, 0.18 ∼ 0.24mm/a, 0.32 ∼ 0. 43mm/a and 0.81mm/a. The four age groups accord better with tectonic-magmatic activity and their developing periods. The new geochronological data and new evidences for the tectonic evolution of Ganzi-Litang gold belt are presented.

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.

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