内蒙古阿拉善地块北缘沙拉扎山晚石炭世岩体地球化学特征与LA-ICP-MS锆石U-Pb年龄  

Geochemistry and LA-ICP-MS zircon U-Pb age of Late Carboniferous Shalazhashan pluton on the northern margin of the Alxa Block, Inner Mongolia and their implications

作　　者：杨奇荻[1] 张磊[1] 王涛[1] 史兴俊[1] 张建军[1,2] 童英[1] 郭磊[1] 耿建珍[3] 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]中国地质大学,北京100083 [3]天津地质矿产研究所,天津300170

出　　处：《地质通报》2014年第6期776-787,共12页Geological Bulletin of China

基　　金：中国地质调查局项目(编号:1212010611803;1212010811033)

摘　　要：采用LA-ICP-MS同位素测定技术，测得内蒙古阿拉善北缘沙拉扎山温都尔毛道黑云母花岗闪长岩锆石U-Pb年龄为301±2Ma，属于晚石炭世侵入岩。地球化学分析结果显示，该黑云母花岗闪长岩SiO2含量为67.23%~72.57%，K2O为1.14%~1.61%，Al2O3为14.92%~17.23%，具有过铝质（A/CNK=1.06~1.1）和钙碱性特征。岩石的稀土元素总量较低（38.86×10-6~74.39×10^-6），轻稀土元素相对富集，Eu总体呈弱异常（δEu=0.9~1.3）。在原始地幔标准化图解中，岩石具有大离子亲石元素（Rb、Th、K）富集及高场强元素（Nb、Ta、P、Ti）亏损的特征，显示出I型花岗岩的特点。结合区域地质背景，该黑云母花岗闪长岩可能形成于俯冲背景，是洋壳板片与新生的壳源物质混合形成的产物，表明晚古生代沿着阿拉善地块北缘的俯冲至少始于301Ma。The Wenduermaodao biotite granodiorite pluton is located in Shalazhashan on the northern margin of the Alxa Block. LA-ICP-MS U-Pb dating of zircons from the pluton yielded an age of 301±2Ma, which indicates that the pluton is a Late Carbonif-erous intrusion. According to the geochemical analysis, the Wenduermaodao pluton has high SiO 2 （67.23%~72.57%）, K2O（1.14 %~6.13%） and Al2O3（13.67%~17.29%）, suggesting that it is calc-alkaline and peraluminous （A/CNK=0.98~1.10）. This intrusion has low REE content （38.86×10-6~74.39×10-6） with a relative enrichment of LREE and week Eu anomalies （δEu=0.9~1.3）. The primitive mantle normalized trace element patterns are characterized by the enrichment of the LILE （Rb, Th, K） and depletion of HFSE （Nb, Ta, P, Ti）, showing the features of I-type granite. Combined with regional geology, the authors hold that the pluton was emplaced in a subduction setting and derived from mixed sources of oceanic crust and juvenile crust, and the subduction of Paleo Asian plate be-neath the northern Alxa Block took place at 301Ma or earlier.

关 键 词：阿拉善 沙拉扎山 晚石炭世 岛弧 LA-ICP-MS锆石U-PB年龄 

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]