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《Chinese Science Bulletin》 2014-22
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Discovery of MOR-type ophiolites from the Dishuiquan region, eastern Junggar

HU ChaoBin;LIAO QunAn;FAN GuangMing;CHEN Shuai;WU WeiWei;TIAN Jian;WANG FuMing;Faculty of Earth Sciences, China University of Geosciences;  
A MOR-type ophiolite unit has been recognized in the Dishuiquan region, 30–40 km to the south of the Karamaili ophiolite in east Junggar, Xinjiang, China. The Dishuiquan ophiolite contains mantle peridotite, pyroxenite, anorthosite, gabbro, basalt, and chert. LA-ICP-MS zircon U-Th-Pb dating of gabbro yielded an age of 416.8±3.2 Ma. The basalts in the Dishuiquan ophiolite are characterized by low Al2O3, TiO2, P2O5, and K2 O levels; high levels of MgO and CaO; and LREE-depleted chondrite-normalized REE patterns. In N-MORB-normalized spider diagrams, the distribution patterns are very similar to those of MORB. The gabbro and pyroxenite have features of cumulate ultramafic-mafic rocks with strongly depleted trace elements. Discrimination diagrams showed that the basalts of the Dishuiquan ophiolite are of MORB and N-MORB type, and are different from the basalts from the Karamaili ophiolite to the north, which are similar to arc basalt. Therefore, the Dishuiquan ophiolite possibly formed in a MOR setting, and represents fragments of the oceanic lithosphere between the Kazakhstan-Junggar plate and the Siberian plate. Based on the regional geology, the Dishuiquan oceanic basin opened before the Ludlow and closed before the Late Devonian. The discovery of Dishuiquan MOR-type ophiolites indicates that the Karamaili ophiolite belt, the age and origin of which are disputed, may be a late tectonic mixture of MOR-type and SSZ-type ophiolites.
【Fund】: 中国地质调查局地质调查项目(1212011120508)资助
【CateGory Index】: P588
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