岩石矿物学杂志2025，Vol.44Issue(4)：870-894,25.DOI:10.20086/j.cnki.yskw.2025.4202
阿拉善东部波罗斯坦庙杂岩含石榴子石黑云斜长片麻岩的p-t演化及独居石U-Pb年龄
Metamorphic p-t evolution and tectonic implications of garnet-bearing biotite-plagioclase gneiss from the Boluositanmiao Complex of the eastern Alxa Block
摘要
Abstract
The Boluositanmiao Complex in the eastern part of the Alxa Block,is one of the high-grade metamorphic complexes,which has important geological significance for the late Paleozoic tectonic evolution of the Alxa Block.In this paper,a combined study of detailed geological investigation,petrography,LA-ICP-MS monazite U-Pb dat-ing and phase equilibrium modeling,were carried out for felsic gneisses of the Boluositanmiao Complex,which is used to reveal their metamorphic evolution and tectonic implications.Felsic gneisses are mainly composed of garnet-bearing biotite-plagioclase gneiss and biotite-plagioclase gneiss.The garnet-bearing biotite-plagioclase gneiss sam-ples ALS2202 and ALS2204 record peak mineral assemblage of garnet+biotite+muscovite+ilmenite+plagioclase+K-feldspar+quartz+melt.Combined with phase equilibrium modeling,the peak p-t conditions of two samples were constrained at 727～751 ℃/820～1 030 MPa and 730～751 ℃/930～1 070 MPa,respectively.In addition,the gar-net-biotite-plagioclase-quartz(GBPQ)geothermobarometry yields relatively low metamorphic p-t conditions of 629～672℃/410～490 MPa and 620～657℃/330～400 MPa,which correspond to the retrograde cooling.Based on the above results,a clockwise p-t evolution was obtained for the garnet-bearing biotite-plagioclase gneiss samples ALS2202 and ALS2204.LA-ICP-MS monazite U-Pb analyses obtained the weighted mean 206Pb/238U ages of 268±4 Ma and 255±2 Ma for the garnet-bearing biotite-plagioclase gneiss sample ALS2207 and the biotite-plagioclase gneiss sample ALS2210,respectively,which may represent the timing of peak metamorphism or anatexis.Based on the mineral assemblage,it suggests that the protolith of these felsic gneisses should be sedimentary rocks.Com-bined with the clockwise p-t path and previously published data in the region,this indicates a significant crustal thickening process in the middle and late Permian,which may be related to the closure of the Paleo-Asian Ocean.关键词
波罗斯坦庙杂岩/LA-ICP-MS独居石U-Pb定年/相平衡模拟/顺时针p-t轨迹/中亚造山带Key words
the Boluositanmiao Complex/LA-ICP-MS monazite U-Pb dating/phase equilibrium modeling/clock-wise p-t path/Central Asian Orogenic Belt分类
天文与地球科学引用本文复制引用
马椰婷,苟龙龙,周峰,田智博..阿拉善东部波罗斯坦庙杂岩含石榴子石黑云斜长片麻岩的p-t演化及独居石U-Pb年龄[J].岩石矿物学杂志,2025,44(4):870-894,25.基金项目
国家自然科学基金项目(41772051) （41772051）
大陆动力学国家重点实验室团队项目(SKLCD04) （SKLCD04）
大陆动力学国家重点实验室开放基金项目(22LCD16) National Natural Science Foundation of China(41772051) （22LCD16）
State Key Laboratory of Continental Dynamics,Northwest University(SKLCD04) （SKLCD04）
Open Fund Project of State Key Laboratory of Continental Dynamics(22LCD16) （22LCD16）
