摘要:中天山卡瓦布拉克地区侵入岩类广泛发育，并多处被中-基性岩脉穿插。LA-ICP-MS锆石U-Pb测年获得闪长岩和辉长岩脉年龄分别为296.1±2.5 Ma （MSWD = 1.4），299.5±2 Ma （MSWD = 1.07），均侵位于早二叠世。岩石学和岩石地球化学分析结果表明该区中-基性岩脉具有富集轻稀土元素（LREE）和大离子亲石元素（Rb，U，Th）、亏损高场强元素（Nb，Ta，Ti）的地球化学特征，SREE为69.19～234.62，LREE/HREE = 3.97～11.18。闪长岩脉锆石（176Hf/177Hf）值为0.280 618～0.283 329，对应的εHf(t) 值为-14.57～+25.06。研究数据表明，该区中-基性岩脉可能起源于亏损岩石圈地幔，原始岩浆在侵位过程中发生了分离结晶作用，同时还受到了地壳混染作用的影响。基于卡瓦布拉克地区中-基性岩脉的野外地质特征和地球化学分析结果，并结合区域地质资料，认为它们形成于南天山洋闭合之后的后碰撞伸展构造背景。
关键词: 岩脉/
年代学/
地球化学/
卡瓦布拉克/
中天山
Abstract:We report zircon U-Pb geochronology, major and trace elements geochemistry and Hf isotopes for the intermediate basic dykes from Kawabulak area in central Tianshan. LA-ICP-MS zircon U-Pb dating yielded a weighted mean 206Pb/238U ages of 296.1±2.5 Ma （MSWD = 1.4） and 299.5±2 Ma （MSWD = 1.07） for diorite and gabbro dykes, respectively. Geochemically, the dykes are characterized by enrichment of LILEs （Rb, U, Th）, LREE and depletion of HFSEs （Nb, Ta, Ti）. SREE varies from 69.19～234.62, while LREE/HREE changes from 3.97～11.18. （176Hf/177Hf） values of zircons from diorite dyke vary from 0.280 618～0.283 329, with corresponding εHf(t) values between -14.57～+25.06. The available data show that parental magma of studied dykes was mainly derived from a depleted mantle and experienced fractional crystallization as well as significant crustal contamination during magma emplacement. Field geological characteristics and geochemical analysis, integrated with regional data from the literature, show that the dykes were likely formed in post-collision extensional environment, indicating that South Tianshan Ocean closed prior to Early Permian in Kawabulak area.
Key words:Dyke/
Zircon U-Pb dating/
Geochemistry/
Kawabulak/
Central Tianshan
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