期刊
CHEMICAL GEOLOGY
卷 294, 期 -, 页码 26-41出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.chemgeo.2011.11.031
关键词
Mafic-ultramafic complex; Petrogenesis; Chinese Altai; CAOB; Ridge subduction
资金
- National Basic Research Program of China [2007CB411308]
- Hong Kong Research Grants Council [HKU704307P, HKU705311P]
- National Natural Science Foundation of China [40721063, 40772130, 40803009]
- HKU CRCG
- Hong Kong-Germany Joint Research Scheme
Devonian magmatism was very intensive in the tectonic evolutionary history of the Chinese Altai, a key part of the Central Asian Orogenic Belt (CAOB). The Devonian Keketuohai mafic-ultramafic complex in the Chinese Altai is a zoned intrusion consisting of dunite, olivine gabbro, hornblende gabbro and pyroxene diorite. The pyroxene diorite gives a zircon U-Pb age of 409 +/- 5 Ma. Variations in mineral assemblage and chemical composition suggest that the petrogenesis of the Keketuohai Complex was chiefly governed by fractional crystallization from a common magma chamber. Low SiO2, K2O and Na2O contents, negative covariations between P2O5, TiO2 and Mg# value suggest insignificant crustal assimilation/contamination. Thus the positive epsilon(Nd)(t) values (0 to + 2.7) and slight enrichments in light rare earth elements (e.g., La/Yb-N = 0.98-3.64) suggest that their parental magma was possibly produced by partial melting of the lithospheric mantle. Model calculation suggests that their parental magma was high-Mg (Mg#=66) tholeiitic basaltic melt. The Keketuohai intrusion was coeval with diverse magmatism, high temperature metamorphism and hydrothermal mineralization, which support a previously proposed model that ridge subduction most likely played an important role in the tectonic evolution of the Chinese Altai. (C) 2011 Elsevier B.V. All rights reserved.
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