成都理工大学学报（自然科学版）2026，Vol.53Issue(1)：169-187,19.DOI:10.12474/cdlgzrkx.2024070301
冈底斯岩浆带春哲地区始新世石英二长岩成因及其构造背景
Petrogenesis and tectonic setting of the Eocene quartz monzonite in the Chunzhe region,Gangdese magmatic belt
摘要
Abstract
Ascertaining the petrogenesis of the Eocene igneous rocks in the Gangdese belt is crucial for understanding Neo-Tethyan subduction and the Indo-Eurasian collision.This study presents field geological,petrographic,zircon U-Pb-Lu-Hf isotopic,and whole-rock geochemical data of an Eocene felsic intrusion in the Luobadui-Milashan fault zone,north of Chunzhe town.Zircon LA-ICPMS U-Pb dating indicates that the igneous rocks were emplaced at(46.9±0.6)to(46.7±0.7)Ma.These zircon grains yield εHf(t)ranging from-2.78 to 0.71,corresponding to TDM2=1 302～1 078 Ma.The samples also contain abundant zircon grains with older apparent ages concentrated at(55.0±1.0)Ma and(50.2±0.7)Ma,whose εHf(t)values vary between-2.49～1.12,and TDM2 spans between 1 289 and 1 054 Ma.These quartz monzonite samples belong to the metaluminous to weakly peraluminous(A/NCK=0.91～1.01),high-K calc-alkaline to alkaline series.They show significant enrichment in light rare Earth elements[(La/Yb)CN:11.19～15.12]and high field strength elements[Zr+Nb+Ce+Y:(459-697)×10-6],as well as moderate Eu depletion(δEu:0.43～0.62),high 104×Ga/Al ratios(2.41～2.61),and high zircon saturation temperatures(TZr:825～862℃).These geochemical features resemble those of A-type granites.The data indicate that the Chunzhe quartz monzonites originated from partial melting of calc-alkaline intermediate-mafic crustal igneous rocks.Combining our data with published results,we propose that the Chunzhe quartz monzonites formed during the transition from the Indo-Eurasian continental collision to the post-collision stage.The continental collision enhanced rollback of the Tethyan oceanic slab(60～50 Ma).Shortly after,breaking off of the oceanic slab(ca.50 Ma)opened a slab window facilitating asthenospheric upwelling,which caused a rise of temperature in the lithosphere.This reactivated the preexisting crustal magma reservoir,and formed the Chunzhe monzonitic pluton.关键词
拉萨地块/冈底斯带/A型花岗岩/石英二长岩/始新世Key words
Lhasa block/Gangdese belt/A-type granite/quartz monzonite/Eocene分类
天文与地球科学引用本文复制引用
康旭,刘毅龙,钟凌林,钟康惠,丁帅,何林,何智远,侯伟,秦覃,KHIN Ei Thu..冈底斯岩浆带春哲地区始新世石英二长岩成因及其构造背景[J].成都理工大学学报（自然科学版）,2026,53(1):169-187,19.基金项目
国家自然科学基金重点项目(42230813) （42230813）
国家重点研发计划(2018YFC0604105). （2018YFC0604105）
