滇东南建水晚古生代枕状熔岩年代学、地球化学特征及构造背景OA

Based on the 1∶50 000 regional geological and mineral survey in Jianshui area of Yunnan Province,a set of pillow lava was determined in the study area,which was scattered on the Triassic clastic rock strata.The weighted average age of 14 zircons obtained by LA-ICP-MS zircon U-Pb dating is 352.3±5.9 Ma(MSWD=1.7),which belongs to the early period of Early Carboniferous and represents the eruption time of lava.The lava has the characteristics of high alkali(Na2O＞K2O,Na2O/K2O=2.93～65.7,average 23.1),high Al(Al2O3=11.43％～16.67％)and low Ti(TiO2=1.71％～2.62％,average 2.16％).It belongs to the subalkaline basalt series.The total amount of rare earth elements of the lava is low,∑REE=101.81×10-6～138.50×10-6,and it is enriched in large ion lithophile elements such as Rb,Ba,Th,K and high field strength elements such as Nb,Ta,etc.,show-ing the characteristics of the large uplift distribution pattern unique to the intraplate basalt,which is similar to the characteristics of OIB.The normalized rare earth element distribution pattern of lava shows a right-leaning distribu-tion pattern enriched in light rare earth elements,which is similar to the characteristics of intraplate basalt or ocean-ic island basalt.Combined with the regional geological background,this paper believes that the Jianshui pillow lava may be a product of the Yangtze and Cathaysian continental blocks controlled by the Paleo-Tethys multi-island ocean system under the early extension of the Late Paleozoic,along with the basic volcanic rocks in the northern section of Shizong-Mile,and the Early Carboniferous pillow basalts in the Longlin area of Jingxi,western Guangxi.