华南加里东期花岗岩地球化学特征及其地质意义

Geological and Geochemical Characteristics of Caledonian Granite Plutons in the Area of Huanan,Jiangxi Province and its Geological Significance

乐安、陡水、宁冈岩体是赣中南加里东期花岗岩的重要组成部分。主量元素显示具有较高的SiO_2含量、K_2O/Na_2O比值和A/CNK比值,属弱过铝质-强过铝质。岩体均富集大离子亲石元素Rb、Th,相对亏损Ba、Sr、P、Ti,Eu亏损相对明显。同时具有稍高的_(εNd)(t)值和相对年轻的Nd模式年龄。ACF、(La/Yb)_N-δEu、_(εNd)(t)-t图解表明属于S型或壳源型花岗岩。在Rb-(Y+Nb)图解中落入后碰撞花岗岩区,表明赣中南加里东期花岗岩形成于后碰撞的伸展构造环境,认为由于当时华南板块加厚地壳的山根垮塌,引起地壳部分熔融作用造成。

Le＇an, Doushui, ninggang as important members of granites formed Caledonian granite in the south of Jiangxi Province, are characterized by higher SiO2 content （an average of 71.58%）, K2O/Na2O ratio （an average of 1.62） ; A/CNK ratio （an average of 1.11） . Is too weak a aluminum strongly peraluminous; rocks are enriched in large ion Pro stone ele- ments Rb, Th, and relatively depleted in Ba, Sr, P, Ti, Eu losses were relatively obvious （an average εEu of 0.31） . Isotopically they have relatively high end （t） value （an average of --6.02） and young Nd model age （an average of 1417Ma） . In the ACF , [w （La） /w （Yb）]N-δEu and εnd （t） -t diagrams they are plotted in the field of S-type or crustal de- rived type granite. In the Rb- （Y＋Nb） diagrams fall into the post collision granite area, show that Caledonian granites were formed in a post collisional extensional tectonic environ- ment, due to crustal thickening of Yamane collapse, causing partial melting of the crust.