Geochemistry, Sr-Nd Isotopes and Tectonic Implications of Two Generations of Late Paleozoic Plutons in Northest Junggar,
详细信息
- 责任者：Chen Jiafu (Key Laboratory of Orogenic Belts and Crustal Evolution ; MOE ; School of Earth and Space Sciences ; Peking University ; Beijing 100871 ; China) ; Han Baofu
- 刊名：Acta Petrologica Sinica
- 出版年：2010
- 卷期：26(8)
- 关键词：侵入体 ; intrusions ; 锶同位素 ; strontium isotopes ; 钕同位素 ; neodymium isotopes ; 准噶尔盆地 ; Junggar Basin
- 页码：p.2317-2335
- 图表：13 illus., 3 tables, 90 refs.
- 分类号：0801
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
Two generations of Late Paleozoic plutons, Early Carboniferous subduction-related plutons and Late Carboniferous-Middle Permian post-collisional A-type granites, were recently recognized in northern West Junggar, Xinjiang, and they are distinguishable by their spatial distribution and geochemistry. Early Carboniferous plutons include diorites, granodiorites, and monzonitic and K-feldspar granites, and they are exclusively restricted within the Late Paleozoic Zharma-Saur arc. The formation of these plutons may be related to the southward subduction of the Irtysh-Zaysan Ocean between Kazakhstan in the south and Altai in the north. Geochemically, they are metaluminous to weak peralunimous, with A/CNK and A/NK ratios of 0.86 ～ 1.03 and 1.24 ～ 1.86, respectively. The data suggest that Early Carboniferous plutons, except for the Abudula monzonitic granite, were probably formed by fractional crystallization of mantle-derived magma which was generated by partial melting of the metasomatized depleted mantle and underwent a magma mixing process.Additionally, the Abudula monzonitic granite was likely to be derived from partial melting of subducted slab. By contrast, Late Carboniferous-Middle Permian plutons, mainly K-feldspar granites, are widespread across all the tectonic units in northern West Junggar and adjacent areas, and they were the products of post-collisional magmatism. The plutons are metaluminous and have A/CNK and A/NK ratios of 0.92 ～ 0.99 and 1.03 ～ 1.27, respectively. Data indicate that Late Carboniferous-Middle Permian A-type granites might be produced by highly fractional crystallization of ascending basaltic magma, which was possibly originated from fluid-metasomatized depleted mantle and mixed with juvenile crustal melts, as a result of slab break-off in a post-collisional setting.
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