过磊,李建星,郭琳,奚仁刚,潘峰.南阿尔金茫崖碱长花岗岩锆石UPb定年及岩石成因研究[J].西北地质,2019,52(1):1-13
南阿尔金茫崖碱长花岗岩锆石UPb定年及岩石成因研究
Zircon U-Pb Dating and Petrogenesis of Alkali-feldspar Granite in Mangnai Area,South Altun,NW China
投稿时间:2018-03-06  修订日期:2018-05-28
DOI:10.19751/j.cnki.61-1149/p.2019.01.001
中文关键词:  锆石U-Pb定年;元素地球化学;岩石成因;碱长花岗岩;茫崖;南阿尔金
英文关键词:petrogenesis;zircon U-Pb dating;alkali-feldspar granite;South Altun;Mongnai
基金项目:国家自然科学基金项目“阿尔金南缘鱼目泉岩浆混合岩体中的矿物成因及岩浆混合过程研究”(41502061)、中国地质调查局地质调查项目“青海1:25万巴什库尔干(J46C001001)、茫崖镇(J46C002001)、幅区调修测(1212011121185)”、“新疆阿拉尔-图木舒克-昆玉综合地质调查”(DD20179605)联合资助
作者单位
过磊 自然资源部岩浆作用成矿与找矿重点实验室, 中国地质调查局西安地质调查中心, 陕西 西安 710054 
李建星 自然资源部岩浆作用成矿与找矿重点实验室, 中国地质调查局西安地质调查中心, 陕西 西安 710054 
郭琳 自然资源部岩浆作用成矿与找矿重点实验室, 中国地质调查局西安地质调查中心, 陕西 西安 710054 
奚仁刚 自然资源部岩浆作用成矿与找矿重点实验室, 中国地质调查局西安地质调查中心, 陕西 西安 710054 
潘峰 自然资源部岩浆作用成矿与找矿重点实验室, 中国地质调查局西安地质调查中心, 陕西 西安 710054 
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中文摘要:
      茫崖碱长花岗岩出露于南阿尔金俯冲碰撞杂岩带内的茫崖镇柴水沟西侧,该岩石具有高的SiO2(75.52%~77.58%),低TiO2(0.16%~0.20%)、Al2O3(11.14%~11.86%)、MgO(0.15%~0.23%)、CaO(0.66%~1.45%)含量,高K/Na(1.32~1.56)值,属高钾钙碱性准铝质系列;稀土元素以轻稀土富集,重稀土平坦,高的稀土总量,明显的Eu负异常,稀土配分曲线呈"海鸥"型式特征;微量元素具有Nb、Ti、P等高场强元素亏损,同时具有Rb、Th、U和K等大离子亲石元素富集的特点,显示为典型的A型花岗岩。南阿尔金茫崖碱长花岗岩锆石LA-ICP-MS U-Pb测年结果为(408.7±1.7)Ma,结合花岗岩岩石成因类型研究和区域研究成果,认为茫崖碱长花岗岩是在南阿尔金伸展拉张背景下,由幔源岩浆底侵作用诱发下地壳部分熔融而成。南阿尔金地区沿阿尔金断裂南缘发育424~385Ma的A型花岗岩,是同一构造-岩浆事件的产物,进一步证实该阶段南阿尔金地区处于一个持续伸展的构造背景。
英文摘要:
      The Chaishuigou alkali-feldspar granite is occurred in Southern Altun subduction-collision complex, which belongs to high-K calc-alkaline and metaluminous series. These rocks have high SiO2(75.52%~77.58%) and K2O/Na2O(1.32~1.56) ratios, but they have low TiO2(0.16%~0.20%), Al2O3(11.14%~11.86%), MgO(0.15%~0.23%) and CaO(0.66%~1.45%) contents. These rocks are characterized by LREE enrichment and depleted HREE, with obvious Eu anomaly and "seagull" REE distribution. They are enriched in large ion lithophile elements (Rb,Th,U,K), while depleted in high field strength elements(Nb,Ti,P). Therefore, the alkali-feldspar granite in Mangnai area is the typical A-type granite. The LA-ICP-MS zircon U-Pb dating results reveal that the alkali-feldspar granite in Mangnai area was formed at ca. (408.7±1.7)Ma. Based on the testing data and some previous research results, it's suggested that alkali-feldspar granite in Mongnai area was formed by partial melting of low crust during the stage of mantle material underplating in extensional tectonic setting. A-type granites (424~385Ma) were formed in the same tectonic-magmatic events in south Altun, indicating that a continuous extensional tectonic setting in the region.
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