摘要
闾井岩体是西秦岭＂五朵金花＂岩体群的成员之一。岩石类型主要为似斑状黑云母二长花岗岩、含斑黑云母二长花岗岩、中细粒黑云母二长花岗岩及粗粒黑云母二长花岗岩。对似斑状黑云母二长花岗岩、粗粒黑云母二长花岗岩和中细粒黑云母二长花岗岩的LA-ICP-MS锆石UPb定年分别获得221±1 Ma（N=20,MSWD=0.11）、221±1 Ma（N=24,MSWD=0.04）和218±1 Ma（N=15,MSWD=0.13）的年龄,表明该岩体形成于晚三叠世,其中似斑状黑云母二长花岗岩比中细粒黑云母二长花岗岩形成略早。该花岗岩的A/CNK=1.02-1.16,Na2O＋K2O=7.65%-8.84%,K2O/Na2O=1.37-1.82,属于过铝质-强过铝质、高钾钙碱性-钾玄岩系列,为I型花岗岩。稀土元素配分曲线为右倾型,轻、重稀土元素分馏明显,具有显著的负Eu异常。地球化学上总体富集Rb、Th、K元素,不同程度亏损Sr、Nb、P、Ti元素。锆石饱和温度计算显示,闾井岩体成岩温度为736-818℃。该岩体与＂五朵金花＂岩体群中的中川岩体具有相似的形成时代及地球化学特征,表明闾井岩体与中川岩体可能具有相似的成岩机制,其外围可能也具有和中川岩体一样的成矿潜力。
The Lujing pluton is one of the ＂Five Golden Flower＂ granite plutons in the Western Qinling. Its main lithologies includes porphyroid biotite admellite, phenocryst-bearing biotite adamellite, medium-fine- grained biotite monzonitie granite and coarse-grained biotite monzonitic granite. The zircon LA-ICP-MS dating for the porphyroid biotite admellite, coarse-grained biotite monzonitic granite and medium-fine-grained biotite monzonitic granite from this pluton yielded ages of 221 _＋ 1 Ma （N = 20, MSWD = 0.11 ）, 221 ± 1 Ma （N = 24, MSWD = 0.04） and 218 ± 1 Ma （ N = 15, MSWD = 0.13）, respectively. These ages suggest that they were formed during Late Triassic and the porphyroid biotite admellite was monzonitic granite. The rocks are of high-K calc-alkaline to formed earlier than the medium-fine-grained biotite shoshonite series and belong to peraluminous to strong peraluminous I-type granites with A/CNK varying trom 1 .02 to 1.16, Na2O＋ K2O from 7.65% to 8.84% and K2O/Na2O from 1.37 to 1.82. Their REE and trace elements are enriched in LREE, Rb, Th and K and differently depleted in Sr, Nb, P and Ti, with strong negative anomalies of Eu （δEu = 0.30-0.70）. Crystallization temperature of the Lujing granites is from 736℃ to 818℃ by zircon thermometer. The geochemical features and formation ages of the Liijing pluton are similar to those of the Zhongchuan pluton, which is also one of the ＂Five Golden Flower＂ granites, suggesting that the Lujing pluton genic potential to the Zhongchuan pluton. may have similar petrogenic mechanism and metallogenie potential to the Zhongchuan pluton.
出处
《岩石矿物学杂志》
CAS
CSCD
北大核心
2016年第1期33-51,共19页
Acta Petrologica et Mineralogica
基金
地质调查项目(12120113090200,1212010611817)
中央级公益性科研院所基本科研业务费专项资金(K1406)
公益性行业专项课题(200911007-09)~~
