中文摘要：

阿拉善地块西南缘沙枣泉石英闪长岩LA-ICP-MS锆石U-Pb年龄302±9．2Ma，SiO2含量在60．66％～61．37％之间，MgO含量在2．13％～2．51％（Mg＊=0．48～0．51）之间，具高AI（AI2O3=17．98％～18．44％），富Ca（CaO=6．08％～6．59％）、富Na贫K（Na2O=4．20％～4．46％，K20=0．67％～0．92％，K20／Na2O=0．16～0．22），以及高Sr（582x10-6～620x10-6），低Y（11．4×10-6～13．7×10-6）、Yb（1．02×10-6～1．51×10-6），高的Sr／Y（35．15～53．25），Y／Yb（11．00～11．23）和La／Yb（7．28～15．10）比值；岩石富集不相容元素（Rb，Th，K，U，Pb等）及LREE，强烈亏损高场强元素Nb，Ta，Ti以及HREE，轻微的正Eu异常（δEu为0．97～1．18，平均值为1．1）。岩体总体特征类似于环太平洋新生代埃达克岩。结合霍尔森一查干楚鲁蛇绿岩年代学及区域内其他花岗岩类地球化学特征认为，沙枣泉埃达克岩是晚石炭世晚期霍尔森一查干楚鲁弧后盆地向南初始俯冲于阿拉善微陆块之下，玄武质洋壳发生部分熔融且与地幔发生一定程度的交代作用、快速上升形成的，指示雅布赖一巴音诺尔公“陆缘弧”建造始于晚石炭世一早二叠世，古亚洲大洋最南端的南蒙古大洋闭合时限应介于275～250Ma之间，为中一晚二叠世。

英文摘要：

The La-ICP-MS zircon U-Pb dating of the Shazaoquan quartz diorites in the southwestern margin of Alxa Block yields a weighted mean age of 302±9.2 Ma. The rocks show SiO2 contents ranging from 60.66% to 61.37%, MgO from 2.13% to 2.51%, and high Na and low K contents （Na20=4.20～4.46%, K20=0.67～0.92%, K20/Na20=0.16～0.22）, and high A1 （A1203=17.98～18.44%）, Ca （CaO= 6.08%～6.59%）, and Sr （582×10-6～620× 10-6） contents, but low Y （ 11.4×10 -6～13.7×10-6） and Yb （ 1.02× 10-6-1.51 × 10-6） contents.They also have high Sr/Y （35.15～53.25） , Y/Yb （11.00～11.23） and La/Yb （7.28～15.10） ratios. The quartz diorites also show enrichment in incompatible elements （Rb, Th, K, U, Pb etc.） and LREE, and strong depletion in high field strength elements, such as Nb, Ta and Ti, and HREE, with slight positive Eu anomalies （δEu=l.1）. The geochemical characteristics of the studied dioritic rocks resemble those of the Cenozoic adakites from the Pacific margin. Together with the regional geological settings, we suggest that the Shazaoquan quartz diorites originated from the partial melting of the subducted basaltic oceanic crusts under the Alxa Block and underwent metasomatization with the surrounding mantle. It also suggests that the formation of Yabulai-Bayinnuoergong arc began in Late Carboniferous-Early Permian and the closure of the southernmost of the Paleo-Asian Ocean occurred between 275～250 Ma.