發(fā)布時間：2018-08-05 15:22

【摘要】：為約束多藏角閃輝長巖的巖石成因和南祁連北緣東段晚奧陶世的構(gòu)造演化,對多藏角閃輝長巖進行了LA-ICP-MS鋯石U-Pb年代學、巖石地球化學和礦物化學分析。結(jié)果表明,角閃輝長巖中鋯石具條痕狀吸收和高的Th/U比值(0.37~1.16),暗示其巖漿成因。巖漿鋯石的206Pb/238 U定年結(jié)果為(444±3)Ma,表明多藏角閃輝長巖形成于晚奧陶世,兩組捕獲鋯石的年齡為520 Ma和484 Ma,代表早期的巖漿事件。多藏巖體具相對低的SiO_2含量(51.68%~55.66%)和高的MgO(4.48%~7.37%)、TiO_2(1.01%~1.24%)、FeO~T(7.99%~8.72%)含量以及高的Mg#值(53~63);LREEs相對富集、HREEs相對虧損,(La/Yb)N=4.03~7.89,具有弱的Eu異常(δEu=0.78~1.16),富集LILEs(Rb、Ba、K)、虧損HFSEs(Nb、Ta),具Sr、P、Ti元素的虧損。結(jié)合礦物化學分析表明,南祁連北緣東段多藏角閃輝長巖起源于受俯沖流體交代的富集巖石圈地幔物質(zhì)的部分熔融,形成于洋-洋匯聚向洋-陸碰撞轉(zhuǎn)換背景下俯沖大洋板片斷離后的伸展構(gòu)造環(huán)境。
[Abstract]:In order to constrain the petrogenesis of multi-reservoir hornblende gabbro and the late Ordovician tectonic evolution in the eastern part of the northern margin of South Qilian, LA-ICP-MS zircon U-Pb chronology, petrogeochemical and mineralogical analysis were carried out for the multireservoir hornblende gabbro. The results show that the zircon in hornblende gabbro has strip-like absorption and high Th/U ratio (0.37 ~ 1.16), indicating its magmatic origin. The 206Pb/238 U dating of magmatic zircon is (444 鹵3) Ma, which indicates that the multi-reservoir amphibolite was formed in the late Ordovician. The ages of two sets of zircon traps are 520Ma and 484Ma. which represent the early magmatic events. 澶氳棌宀╀綋鍏風浉瀵逛綆鐨凷iO_2鍚噺(51.68%~55.66%)鍜岄珮鐨凪gO(4.48%~7.37%),TiO_2(1.01%~1.24%),FeO~T(7.99%~8.72%)鍚噺浠ュ強楂樼殑Mg#鍊，

本文編號：2166198