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.%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。
展开▼
