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福建中部龙岭花岗岩LA-ICP-MS锆石U-Pb测年
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Abstract:
龙岭花岗岩位于福建省中部，总体呈南北向展布，出露面积约为120 km2，岩性为灰白色似斑状二长花岗岩和二长花岗岩。前人将其时代划归为二叠纪或石炭纪，但地质图显示其上与上泥盆统天瓦岽组呈沉积不整合接触。为了确定龙岭花岗岩的形成时代，本文对龙岭花岗岩进行了LA-ICP-MS锆石U-Pb测年，获得206U/238Pb加权平均年龄为432.8 ± 4.8 Ma (n = 20, MSWD = 0.0092)，表明龙岭花岗岩侵位时代为志留纪，是加里东期岩浆活动的产物，而不是二叠纪或石炭纪侵位的花岗岩，这对华夏地块早古生代岩浆演化提供了新资料。
The Longling granite is located in the central part of Fujian Province, which is distributed in a north-south direction and the distribution area is about 120 km2. It is mainly composed of gray-white porphyritic monzonitic granite and monzonitic granite. The predecessors classified its age as Permian or Carboniferous; however the geological map shows that it is in sedimentary unconformity contact with the Upper Devonian Tianwadi Formation. In order to determine the formation age of the Longling granite, this paper has carried out LA-ICP-MS zircon U-Pb dating on the Longling granite. The weighted average age of 206U/238Pb is 432.8 ± 4.8 Ma (n = 20, MSWD = 0.0092), indicating that the intrusive age of the Longling granite is the Silurian, which is the product of Caledonian magmatic activity, rather than the Permian or Carboniferous, and which provides new data for the early Paleozoic magmatic evolution of the Cathaysia block.
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