敦煌地块晚石炭世二长花岗岩年代学、地球化学特征及地质意义  

Chronology and Geochemistry for Late Carboniferous Monzogranite in Dunhuang Block and Its Geological Significance

作　　者：杨国林 任文秀[2] 李军 丁仨平 梁明宏[2] 欧阳征健 Yang Guolin;Ren Wen xiu;Li Jun;Ding Sanping;Liang Minghong(BaiLie School of Petroleum Engineering,Lanzhou City University,Lanzhou,Gansu,730070,China;Gansu Geological Survey Institute,Lanzhou,Gansu,730000,China;College of Geography and Environmental Engineering,Lanzhou City University,Lanzhou,Gansu,730070,China)

机构地区：[1]兰州城市学院培黎石油工程学院,甘肃兰州730070 [2]甘肃省地质调查院,甘肃兰州730000 [3]兰州城市学院地理与环境工程学院,甘肃兰州730070

出　　处：《新疆地质》2022年第3期417-424,共8页Xinjiang Geology

基　　金：甘肃省自然科学基金项目(20JR5RA039);甘肃省区域地质调查片区总结与服务产品开发项目(12120113013500);兰州城市学院博士科研启动基金项目(LZCU-BS2018-11);甘肃省高等学校创新基金项目(2021B-284);兰州城市学院博士科研启动基金项目(LZCU-BS2019-03);兰州城市学院2019年本科教学建设与改革项目(2019-jy-18)共同资助。

摘　　要：为厘清白墩子二长花岗岩体的形成时代、成因及构造环境,对其开展了LA-ICP-MS锆石U-Pb同位素测年和地球化学特征分析。该岩体锆石^(206)Pb/^(238)U同位素加权平均年龄为(306.1±5.3)Ma,时代为晚石炭世。该岩体具有较高的Al_(2)O_(3)(13.09%~14.05%)和SiO_(2)(72.14%~75.71%)、较低的CaO(0.89%~1.34%);轻重稀土元素分馏相对明显[(La/Yb)_(N)=13.35~18.83],LREE/HREE=6.66~17.40,稀土总量较低(∑REE=60.40×10^(-6)~81.24×10^(-6)),弱Eu负异常(δEu=0.44~1.24),稀土元素分布图呈右倾型特征;在微量元素蛛网图上,亏损高场强元素(HFSE)Nb,Ta,Sr,相对富集大离子亲石元素(LILE)Th,Rb,Pb。白墩子二长花岗岩体具较高Sr/Y比、低Yb、弱Eu负异常特征、Mg^(#)值为16.95~21.58,说明该岩体可能为加厚下地壳部分熔融的产物。结合岩体地质特征和区域地质背景,认为白墩子二长花岗岩体可能形成于板内伸展构造环境。In order to clarify the formation age,genesis and tectonic setting of the Baidunzi monzogranite,LA–ICP–MS zircon U-Pb isotopic dating and geochemical characteristics were analyzed.The results show that the zircon^(206)Pb/^(238)U isotope-weighted mean age is 306.1±5.3 Ma,which is at the turn of the Late Carboniferous.The Granite has higher content of Al_(2)O_(3)(13.09%~14.05%)and SiO_(2)(72.14%~75.71%),low content of CaO(0.89%~1.34%).Enrichment in LREE and relatively depletion in HREE[(La/Yb)_(N)=13.35~18.83],LREE/HREE=6.66~17.40,and have low REE(∑REE=60.40×10^(-6)~81.24×10^(-6)),with slightly Eu anomalies(δEu=0.44~1.24).The rare earth element distribution patterns display as right–leaning.The Baidunzi monzogranite are characterized by high ratio of Sr/Y,low Yb,weak negative Eu anomaly and Mg^(#)values ranging from 16.95 to 21.58,indicating that the Granite,may be the product of partial melting of the thickened lower crust.Combined with geological characteristics of rock mass and regional geological background,it can be concluded that the Baidunzi monzogranite was formed in intraplate extensional tectonic setting.

关 键 词：敦煌地区 二长花岗岩 U-PB测年 晚石炭世 

分 类 号：P534.45[天文地球—古生物学与地层学] P597.3[天文地球—地质学] P595