摘要
本文报道了福建省范围内前人分析数据稀疏或空白区域内的１８个古生代－中生代花岗岩体的Ｎｄ、Ｓｒ同位素组成：εＮｄ（ｔ）＝－３．６～－１６．４，（８７Ｓｒ／８６Ｓｒ）ｉ＝０．７０５５～０．７３１８，ｔＤＭ＝１．２～２．３Ｇａ。结合前人分析数据，区分出三个地域区带：福安－南靖断裂以东的沿海带：εＮｄ（ｔ）＝－１．５～－６．８，（８７Ｓｒ／８６Ｓｒ）ｉ＝０．７０５６～０．７０９９，ｔＤＭ＝１．１～１．４５Ｇａ，弧后伸展构造背景下的幔－壳岩浆混合是该带花岗岩的主要成岩方式；福安－南靖断裂以西的内陆区域：εＮｄ（ｔ）＝－４．０～－１６．４，（８７Ｓｒ／８６Ｓｒ）ｉ＝０．７０６４～０．７４１０，ｔＤＭ＝１．３～２．３，其中加里东－印支期花岗岩主要由与麻源群相当之地壳物质部分熔融形成，而燕山期花岗岩，一部分由与麻源群相当或较年轻的地壳物质部分熔融产生，也有一部分可能由壳－幔岩浆混合形成；福建省南部的纬向带：εＮｄ（ｔ）＝－３．６～－７．５，（８７Ｓｒ／８６Ｓｒ）ｉ＝０．７０５５～０．７０９９，ｔＤＭ＝１．２～１．５５，同位素特征与沿海带相似。
Proterozoic Mesozoic granitoids in Fujian analysed here have ranges of ε Nd ( t ) value of -3 6 ￣ -16 4, initial 87 Sr/ 86 Sr ratio [( 87 Sr/ 86 Sr) i ] of 0 7055￣0 7318, and Nd model age ( t DM ) of 1 2￣1 3Ga These data, together with previously published data, enable us to distinguish three zones/areas where granitoids have different Nd and Sr isotopic compositions, ways of formation and tectonic significances In the coast zone east to the Fu'an Nanjing Fault, the granitoids have high ε Nd ( t ) value (-1 5￣-6 8), low( 87 Sr/ 86 Sr) i ratio (0 7056￣0 7099) and t DM age (1 1￣1 45Ga) Mixing of magmas derived from mantle and crust under a tectonic extension in the back arc during the Cretaceous was the main way of the granitoid formation Granitoids in the inland area west to the Fu'an Nanjing Fault have low ε Nd ( t ) value (-4 0 ￣ -16 4), high( 87 Sr/ 86 Sr) i ratio (0 7064￣0 7410) and t DM age (1 3￣2 3Ga). The Caledonian and Indosinian granotoids were mainly derived from crustal materials similar to the basement metamorphic rocks of the Mayuan Group. Part of the Yanshanian grantoids were also derived from Mayuan Group like crust, while part of them may have been formed by mixing of mantle and crust derived magmas. In the south of Fujian, there is an east west trend zone with Nd and Sr isotopic compositions of grantoids [ ε Nd ( t )=-3 6￣-7 5, ( 87 Sr/ 86 Sr)Si =0 7055￣0 7099, t DM =1 2￣1 55] similar to those of the coast zone. However, the tectonic extention may have developed earlier than that in the coast zone.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
1999年第2期255-262,共8页
Acta Petrologica Sinica
基金
国家自然科学基金
关键词
同位素组成
花岗岩
古生代
锶
钕
Nd and Sr isotopic compositions, Granitiods, Paleozoic and Mesozoic Period, Fujian Province
