Petrology and geochemistry of a +epsilon(Nd) gabbro body in Baluntai region, central Tianshan mountains, Xinjiang.

新疆巴仑台附近出露的辉长岩(骆驼沟岩体)是中天山地区出露最大的晚石炭世基性侵入体,该岩体分带明显,由边部的细粒辉长玢岩(冷凝边)逐渐过渡到内部的中粗粒辉长玢岩。中粗粒辉长玢岩的ε_(Nd)值(+5．10～+5．74)和初始~(87)Sr/~(86)Sr比值(0．7055～0．7058)变化很局限,但边缘相细粒辉长玢岩的ε_(Nd)值(+4．25～+7．28)变化较大而初始~(87)Sr/~(86)Sr值(0．7058～0．7059)变化较小。三个细粒辉长玢岩全岩样品构成一条Rb-Sr等时线,等时线年龄321±10Ma(MSWD=1．5,初始~(87)Sr/~(86)Sr值0．705725±0．...The Luotuogou gabbro, in the Baluntai region of the Central Tianshan Mountains is a large mafic intrusive body formed during the Late Carboniferous period. This pluton is clearly zoned with a thin rim (width 50 similar to 200m). The rim is composed by the fine-grained porphyritic gabbro, which gradually changed to medium-and coarse-grained gabbro (the major body of the Luotuogou pluton). The medium to coarse-grained gabbro samples have high and less variable + epsilon(Nd) values (+ 5.10 similar to + 5.74) and high initial Sr-87/(86) Sr values (0.7055 similar to 0.7058). The fine-grained gabbro samples have largely variable epsilon(Nd) values (+ 4.25 similar to + 7.28) and relatively high initial Sr-87/(86) Sr ratios (0.7058 similar to 0.7059). Three samples of the fine-grained gabbro composed a Rb-Sr isochron, which yielded an age of 321 +/- 10Ma (MSWD = 1.5, initial Sr-87/(86) Sr = 0.705725 +/- 0. 000084). This age is close to the zircon SHRIMP age of the trachandesite (313Ma) distributed in the northwest of Baluntai region. Similar to the Late Carboniferous trachyandesite, the Luotuogou gabbro is enriched in La, Sr and Ba. High + epsilon(Nd) values indicate that the studied gabbro has a geochemical nature of depleted mantle. However, the obvious high initial Sr-87/(86) Sr ratios suggest that the Luotuogou gabbro was not derived directly from the partial melting of the lithosphere mantle but could be formed by the mixing (or AFC process) between magma from depleted mantle and the La-, Ba-, and Sr-rich felsic magma (or volcanic rocks).http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000239220600010&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701SCI(E)中文核心期刊要目总览(PKU)中国科技核心期刊(ISTIC)中国科学引文数据库(CSCD)19051178-11922