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Beijing, China

Wu G.,Chinese Academy of Geological Sciences | Wu G.,CAS Guangzhou Institute of Geochemistry | Wu G.,Lingbao Jinyuan Mining Ltd Liability Company | Chen Y.,Chinese Academy of Geological Sciences | Chen Y.,Pelting University
Acta Petrologica Sinica | Year: 2010

A lot of epithermal gold deposits and occurrences, such as Arharlei and Wurenkebulake deposits, have been found in the northeastern Kazakhstan Tianshan, which is one of the important epithermal gold metallogenic belts in the Central Asian Orogenic Belt Whereas, the metallogenetic chronology study of the gold deposits is poor. To time the mineralization, the authors dated andesite and andesitic basalt from the host rocks of the Arharlei and Wurenkebulake deposits, respectively, using high-resolution laser-ablation 40Ar/ 39 Ar method. Twenty analyses of andesites from the Arharlei deposit yielded a 40Ar/39 Ar isochron age of 304 ± 7Ma ( MSWD =6) , and 21 of andesitic basalts from the Wurenkebulake deposit deposit yielded a 40Ar/39 Ar isochron age of 280 ± 6Ma (MSWD =2.4). This shows that the gold deposits in the northeastern Kazakhstan Tianshan have been formed between end Late Carboniferous and Early Permian. Petrology and geochemistry primarily studied by the authors show that the volcanic rocks related to these epithermal gold deposits in this region are mainly of high-K calc-alkaline and shoshonite series, and comprise mainly rhyolite, trachyandesite, basaltic trachyandesite, basaltic andesite, trachybasalt and basalt, with hi modu I features. The epithermal gold deposits of the end Late Carboniferous might be formed in a transitional period from continent-continent collision to rift environments, whilst the Permian epithermal gold deposits were formed in an irilraeonlmental rift setting.

Liu X.,Pelting University | Liu X.,Pelting University | Hu Z.,Pelting University | Hu Z.,Pelting University | And 2 more authors.
Acta Petrologica Sinica | Year: 2010

As one of the most important minerals in geology, feldspar might enter the deep interior of the Earth via slab subduction process. Consequently, its phase relations and physical-chemical behaviors at high pressures could be very significant to the geodynamic process of the Earth's interior. Here we summarized in some phase diagrams all known high pressure-high temperature expérimental data about feldspars with various compositions. These phase diagrams evident that a full picture about feldspar at high pressure is still unavailable, so that further high-pressure experimentation is necessary. Additionally, we briefly reviewed the available physical properties of the high-pressure phases derived from the feldspar compositions, and integrated them into pressure-density profiles which were subsequendy compared to the pressure-density profile of pyrolite. The comparison suggested that the density of the different high-pressure phase assemblages for the feldspar compositions is larger than that of the pyrolite for the pressure interval of - 5 to 23GPa, leading to positive sinking into the upper mantle of the Earth.

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