摘要
热水岩体位于贵东岩体中部南侧,SHRIMP锆石U-Pb定年结果为162.8±5.8 Ma(MSWD=4.2),属于燕山早期岩浆活动产物。该岩体具有富硅(SiO2平均为76.32%)、富铝(A/CNK值平均为1.14)、钾大于钠(K2O/Na2O值平均为1.32)和高的P2O5含量(平均为0.41%);大离子元素富集,Ba、Sr、Ti、Nb、Ta亏损,具有高的Rb/Sr(平均为28.5)和Rb/Nb值(平均为19.8);轻、重稀土之间分馏不明显,配分模式呈水平型,Eu亏损明显(δEu值平均为0.14);εNd(t)值低(平均为-10.2),Nd模式年龄古老(平均为1777 Ma);岩浆源区物质由泥质岩组成。这些特征表明,热水岩体属于典型的S型或壳源型花岗岩。热水岩体可能是在燕山早期太平洋板块俯冲导致先存的东西向大东山-贵东断裂带重新复活的构造背景下,由古—中元古代泥质变质岩低程度部分熔融的方式形成。
The Reshui granite is located at south of the Guidong composite granite.SHRIMP zircon U-Pb dating yields an age of 162.8±5.8 Ma（MSWD=4.2）,suggesting its formation in the Early Yanshanian period.This granite is characterized by high silicon（average SiO2=76.32%）,aluminum（average A/CNK1.14） and phosphorus（average P2O5=0.41%）,and potassium higher than sodium（average K2O/Na2O=1.32）.It is also enriched in Rb,Th,Ce,Sm and Y,but depleted in Ba,Sr,Ti,Nb and Ta,with high Rb/Sr values（average of 28.5） and high Rb/Nb values（average of 19.8）.Its light and heavy rare earth elements are not well fractionated,having flat chondrite-normalized REE patterns with clear Eu depletion（average δEu=0.14）.The initial εNd（t） values of the rocks are generally low（averaging at-10.2） and the Nd isotope model ages are of Mesoproterozoic（averaging at 1777 Ma）.Source rock discriminating suggests pelite for the origin of the granite.All these above point to S-type granite affinity for the Reshui granite.Under the tectonic environment of subduction of the paleo-Pacific Plate in the Early Yanshanian period,which revivified the pre-existed Dadongshan-Guidong fault,the Reshui granite was formed from a granitic magma probably generated by low-degree partial melting of the Early Mesoproterozoic meta-pelite in the source.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2011年第8期1274-1283,共10页
Acta Geologica Sinica
