摘要:对新疆库鲁克塔格西段乌斯腾高勒东南橄榄辉长岩进行系统的锆石U-Pb年代学、全岩地球化学及Sr?Nd?Hf同位素研究，确定了岩石成因，并探讨其构造背景及地质意义。LA-ICP-MS锆石U-Pb年代学研究表明，橄榄辉长岩结晶年龄为410.3±5.7 Ma （MSWD = 0.56），属早泥盆世岩浆活动的产物。全岩地球化学表明，岩石具有高Al2O3 和CaO、贫碱、低P2O5和TiO2的特征，属于低钾拉斑系列；岩石具有较高的Mg#值（72.27～75.04）、明显的Eu正异常（δEu = 1.12～1.38），其轻稀土元素轻微富集，重稀土元素相对平缓；微量元素蛛网图上岩石富集大离子亲石元素（如Rb、Ba、K、Sr）和Pb元素，亏损高场强元素（如Nb、Ta、P、Ti）。全岩Sr 同位素初始比值（87Sr/86Sr）i值（0.703 663～0.704 013）相对较小，εNd（t）值（-2.32～+4.98）变化范围较大，锆石εHf（t）值为+7.8～+12.5。该岩体为俯冲板片流体改造过的相对较浅、对应于尖晶石二辉橄榄岩稳定区域的亏损地幔楔部分熔融，部分熔融比例在2%～10%之间，其母岩浆形成过程中遭受低程度的地壳物质混染，并经历了斜长石的堆晶作用和较弱的橄榄石和单斜辉石的结晶分异作用。结合区域已有地质资料，本文认为塔里木北缘库鲁克塔格地区在古生代中期经历了南天山洋南向俯冲过程，橄榄辉长岩产于主动大陆边缘环境，该时期大陆地壳生长方式为垂向生长，指示塔里木北缘具有增生造山带的属性。
关键词: 橄榄辉长岩/
早泥盆世/
主动大陆边缘/
垂向生长/
库鲁克塔格/
塔里木北缘
Abstract:Systematic studies on the zircon U-Pb chronology, whole rock geochemistry and Sr Nd Nd Hf isotope of the southeastern olibogabbro of Wustengoler in the western Kuruktuggi section of Xinjiang have confirmed the origin of the rocks and discussed their tectonic background and geological significance. LA-ICP-MS zircon U-Pb geochronology study shows that the crystallization age of olivine gabbro is 410.3±5.7 Ma （MSWD = 0.56）, which belongs to the Early Devonian magmatic product. All rock geochemistry shows that rocks are characterized by high Al2O3 and CaO, poor alkali, low P2O5 and TiO2 which belongs to low potassium thallus series; In addition, rocks have high Mg# value （72.27～75.04）, obvious Eu positive anomaly （δEu = 1.12～1.38）, LREE are slightly enriched, HREE are relatively gentle; In the trace elements cobweb the rocks are enriched with large ion lithophile elements （Rb, Ba, K, Sr） and Pb, and depleted of high field-strength elements Nb, Ta, P and Ti. The whole rock （87Sr/86Sr）i value （0.703 663～0.704 013） is relatively small, and the range of εNd（t） value （-2.32～+4.98） varies greatly, and the value of zircon εHf（t） is +7.8～+12.5. The comprehensive analysis shows that the magma of rock mass originates from the partial melting of the depleted mantle wedge in the stable area of spinel-lherzolite, which is relatively shallow and has been modified by the subduction plate fluid, and the proportion of the partial melting is between 2%～10%. The magma formed by it has been exposed to a low degree of crustal contamination during the evolution process, and has experienced apocrystalline action of plagioclase and the crystallization of the stone and the weaker olivine and clinopyroxene. Combining with the geological data in the region, this paper suggests that the northern margin of the Tarim has experienced that South Tianshan oceanic subducted towards south in the middle Palaeozoic, and the olivine gabbro is produced on the active continental margin, The growth mode of continental crust during this period was vertical, indicating that the northern margin of Tarim had the property of an accretionary orogenic belt.
Key words:Olivine gabbro/
Early Devonian/
Active continental margin/
Vertical growth/
Kuruktag/
The northern margin of Tarim
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