李卫红,王军,李小强,王玉玺.阿尔金东段当金山口中酸性侵入体年代学、地球化学特征及构造意义[J].西北地质,2020,53(4):34-50 LI Weihong,WANG Jun,LI Xiaoqiang,WANG Yuxi.Chronology, Geochemical Characteristics of the Intermediate Acid Intrusives in Dangjinshankou, Eastern Altun and Their Tectonic Significance[J].Northwestern Geology,2020,53(4):34-50
阿尔金东段当金山口中酸性侵入体年代学、地球化学特征及构造意义
Chronology, Geochemical Characteristics of the Intermediate Acid Intrusives in Dangjinshankou, Eastern Altun and Their Tectonic Significance
投稿时间:2019-12-12  修订日期:2020-08-21
DOI:10.19751/j.cnki.61-1149/p.2020.04.004
中文关键词:  寒武纪;地球化学;构造意义;阿尔金东段;当金山口
英文关键词:Cambrian;geochemistry;tectonic significance;eastern Altun;Dangjinshankou
基金项目:2020年陇原青年创新创业人才项目“地学大数据综合产品研发与应用—甘肃金川超大型铜镍矿深部及外围找矿研究”、“全国自然资源要素综合观测网络建设与运行(2020)”和“甘肃调查数据集成与综合研究”联合资助
作者单位
李卫红 甘肃地矿科技信息中心, 甘肃 兰州 730000 
王军 甘肃省地质调查院, 甘肃 兰州 730000 
李小强 甘肃省地质调查院, 甘肃 兰州 730000 
王玉玺 甘肃省地矿局第三地质矿产勘查院, 甘肃 兰州 730050 
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中文摘要:
      阿尔金东段当金山口侵入体主要由花岗岩、花岗闪长岩和闪长岩构成。LA-ICP-MS锆石U-Pb同位素定年,获得当金山口花岗岩的206Pb/238U的加权平均年龄为(518±13) Ma,表明侵位时代为早寒武世。岩石地球化学研究表明,该岩体具有较高的SiO2含量,全碱Na2O+K2O含量平均为6.46%,岩石表现为兼有富钠和富钾的特征,但以富钠为主,具有较低的Fe2O3、P2O5、MgO含量。稀土元素总量∑REE为47.28×10-6~368.74×10-6,均值为225.37×10-6,整体表现出轻重稀土分馏明显,δEu为0.45~1.08,均值为0.83,略有负Eu异常,富集高场强元素,亏损大离子亲石元素,其中HFSE元素中Th、Ce、Zr、Hf等富集,而Nb、Ta表现出轻微亏损,而LILE元素中Ba、Sr、Eu表现为亏损,Rb表现为强富集,主要为钙碱性-高钾钙碱性系列准铝质-过铝质岩石。通过对岩石成因及构造环境分析,认为本区侵入体可能形成于消减俯冲火山弧环境及后期同碰撞构造环境下,以壳源角闪岩相基性岩为主的部分熔融,并有幔源物质参与。结合区域地质资料对比显示,阿尔金东段当金山口侵入体与西侧南阿尔金蛇绿混杂岩带和东侧祁连造山带古生代花岗质岩浆活动事件及构造背景存在较好的对比性。
英文摘要:
      The Dangjinshankou intrusive body in eastern Altun is mainly composed of granite, granodiorite and diorite. LA-ICP-MS zircon U-Pb isotopic dating shows that the weighted average age of 206Pb/238U of Dangjinshankou granite is (518±13) Ma, indicating that the emplacement age is early Cambrian. Geochemistry shows that the rock mass has a high content of sio2, and the average content of total alkali Na2O + K2O is 6.46%. The rock is rich in both sodium and potassium, but mainly rich in sodium, with low content of Fe2O3, P2O5 and MgO. The total amount of rare earth elements ∑REE is 47.28×10-6-368.74×10-6, with an average value of 225.37×10-6. As a whole, the heavy and light rare earth fractionation is obvious, δEu is 0.45-1.08, with an average value of 0.83. Negative europium is slightly anomaly, high field strength elements are enriched, and large ion lithophile elements are depleted. In HFSE elements Th, Ce, Zr, Hf are enriched while Nb, Ta are slightly depleted. In LILE elements Ba, Sr, Eu appear depleted. Rb shows strong enrichment. The granite belongs to quasi aluminous peraluminous rocks of calc-alkaline high-K calc-alkaline series. The analysis of petrogenesis and tectonic environment indicates that the intrusions in this area may form under the environment of subduction volcanic arc and later syn-collision, with the partially melted basic rocks of amphibolite facies and the participation of mantle materials. The regional geological data shows that Dangjinshankou intrusive body has a lot in common with the granitic magma activities and tectonic setting in the ophiolite belt and the Qilian orogenic belt.
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