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Chen X.,Hunan University of Science and Technology | Chen X.,Hunan Provincial Key Laboratory of Shale Gas Resource Utilization | Wang Y.,CAS Guangzhou Institute of Geochemistry | Han H.,Petrochina | And 3 more authors.
Jilin Daxue Xuebao (Diqiu Kexue Ban)/Journal of Jilin University (Earth Science Edition) | Year: 2014

Basic dikes occurring within the Dongfangzhongsha farmland in SW Hainan Island are mainly composed of plagioclase, monoclinic pyroxene and a small amount of hornblende. These basic dikes are charactered by such geochemical features as SiO2=52.39%-53.44%, K2O+Na2O=5.02%-5.71%, K2O=2.45%-3.29% and high K2O/Na2O value of 0.91-1.63. These rocks are also featured by enrichment in LREEs and LILEs, slight Eu negative anomaly (δEu=0.76-0.84), insignificant Sr and P negative anomalies as well as significant Nb-Ta and Ti negative anomalies. These signatures show these basic dikes may come from fluid metasomatic mantle resource. The representative basic dike (11HN31A) yielded the LA-ICP-MS zircon U-Pb ages of (242.2±2.6) Ma with MSWD=0.074 (n=14), interpreted as the crystallization age, which is consistent with those in east Hainan Island. Our new data, together with the available data, indicate the Indosinian basic dikes formed under the post-orogenic extensional tectonic setting in Hainan Island, in Early Triassic (-240 Ma). Source


Dai D.,Hunan University of Science and Technology | Dai D.,Chinese Academy of science | Yang R.,Hunan University of Science and Technology | Yang R.,Hunan Provincial Key Laboratory of Shale Gas Resource Utilization | Chen X.,Hunan University of Science and Technology
Earth Science Frontiers | Year: 2014

Meteorite samples can be better preserved in Antarctic ice sheet and arid desert regions. Forty-seven desert meteorites were collected from Xinjiang during the meteorite expedition since April to May, 2013. Petrography and mineral chemistry of the 6 samples of them have been studied, in order to determine their chemical-petrographic types. Modal compositions of the Arlatager 004, 006, 0014, 0022 and TuzLeik001 meteorites are similar, mainly consisting of olivine, low-Ca pyroxene, metallic Fe-Ni and troilite. Due to intensive thermal metamorphism the spherulitic textures in the chondrules are poorly defined, with only a few fragments remaining spherulitic. The olivine and low-Ca pyroxene in these meteorites are similar in composition, which in some degree reflects the thermodynamic equilibrium during their development. According to the structures of chondrules and mineral chemistry there are 5 petrographic types to be classified. The four meteorite samples (Arlatager 004, 006, 0014 and 0022) are classified into chemical group L, and TuzLeik001 is classified into chemical group H. Kumtag005 meteorite sample shows typical spherulitic texture, combined with its Fa value in olivine and ferrosilite content (Fs) in low Ca pyroxene and its petrographical features,it is assigned to common chondrite of L3 type.Based on Percent Mean Deviation (PMD) of Fa content of olivine and its correction with petrographic subtype of unequilibrated meteorites, Kumtag005 is subdivided as L3.4. The 6 samples of meteorites belong to 3 chemical groups, combining the other analytical results of meteorites collected from this region, it is suggested that the desert of Hami in Xinjiang is likely a new meteorite-enriched region. The collection and study of desert meteorite will help to promote the development of meteoritics and cosmochemistry in China. Source


Dai D.,Hunan University of Science and Technology | Dai D.,Chinese Academy of science | Chen X.,Hunan University of Science and Technology | Yang R.,Hunan University of Science and Technology | Yang R.,Hunan Provincial Key Laboratory of Shale Gas Resource Utilization
Scientia Geologica Sinica | Year: 2013

Ca-, Al-rich inclusions, chondrules and amoeboid olivine aggregates are the early assemblages of the solar nebula. 4 olivine and Ca, Al-rich assemblages were studied to compare with their petrography and mineral chemistry. The petrography and mineral chemistry characteristics argues that spinel-pyroxene-rich inclusion embedded in olivine and Ca, Al-rich amoeboid olivine aggregates are likely assemblages of solar nebular condensates. The plagioclase-olivine inclusions(POIs) and Ca-, Al-rich chondrules were crystallized from melts. The characteristics of mineral modal compositions of POIs and Ca-, Al-rich chondrules argues they probably represent intermediate assemblages between typical refractory inclusions and chondrules. Spinel in amoeboid olivine aggregates(GRV022459-2C1) is the most remarkably FeO-rich in all assemblages, and it indicates alteration of the aggregate happened under high oxygen fugacity. Chondrules and coarse-grained Ca-, Al-rich inclusions are probably crystallized from melt in the same affair. The coarse-grained Ca-, Al-rich inclusions form probably the reservoir of Ca-, Al-rich prior matters, and Mg, Fe silicate chondrules form in the reservoir of Ca-, Al-poor prior matters. POIs and Ca-, Al-rich chondrules form the district between coarse-grained inclusions and Mg, Fe silicate chondrules. Source


Chen X.,Hunan University of Science and Technology | Chen X.,Hunan Provincial Key Laboratory of Shale Gas Resource Utilization | Wang Y.,CAS Guangzhou Institute of Geochemistry | Zhang Y.,CAS Guangzhou Institute of Geochemistry | And 2 more authors.
Geotectonica et Metallogenia | Year: 2013

The Nandu syenite shows SiO2=62.7%~64.2%, K2O+Na2O=11.2%~12.3%, K2O=6.47%~9.06% with high K2O/Na2O of 1.37~2.80. It can be defined as shoshonitic series rocks. These rocks are characterized by enrichment of LREE and LILE, with slight Eu negative anomalies (δEu=0.48~0.74), and significant Sr and P-Ti negative anomalies but insignificant Nb-Ta negative anomalies. Their εNd(t) values range from +0.32 to +0.84. Such signatures show an affinity to intraplate shoshonitic rocks. LA-ICP-MS zircon U-Pb dating of the Nandu syenite yields an age of 162±1 Ma with MSWD=0.1 (n=23), which is interpreted as the crystallization age. Such an age is consistent with those in southeast Guangxi and south Jiangxi provinces. Our new data, together with the available data, indicate a middle Jurassic intraplate extensional tectonic regime in South China. Source


Dai D.,Hunan University of Science and Technology | Dai D.,Chinese Academy of science | Zhou C.,Hunan University of Science and Technology | Chen X.,Hunan University of Science and Technology | Chen X.,Hunan Provincial Key Laboratory of Shale Gas Resource Utilization
Earth, Moon and Planets | Year: 2015

Two new carbonaceous chondrites, GRV 023155 and GRV 050179, collected from the Grove Mountains (GRV), Antarctica, have been classified as the oxidized CV3 and CM2 chondrites, respectively.  A total of 9 Ca-, Al-rich inclusions (CAIs) were found in the two meteorites. Most of the inclusions are extensively altered, with phyllosilicates commonly found in the alteration assemblages of CAIs, chondrules and matrix in the GRV 050179 CM2 chondrites, suggesting that aqueous alteration occurred on the host meteorite parent body. In contrast, feldspathoids and hedenbergite were identified in the CAIs from GRV 023155. The FeO-rich phases in the CAIs from GRV 023155 indicate alteration of these CAIs happened under high oxygen fugacity. All 9 inclusions can be classified as Type A or spinel-pyroxene rich inclusions, and they probably represent a continuum of solar nebular condensation. The survey of Ca-, Al-rich inclusions in GRV 023155 (CV3) and 050179 (CM2) suggests that Type A and spinel-pyroxene inclusions are common in these two meteorites. © 2015, Springer Science+Business Media Dordrecht. Source

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