摘要
对苏州Ａ型花岗岩氢氧同位素组成进行了系统深入的研究，其全岩δ１８Ｏ值为＋３．５‰～＋９．２‰，全岩δＤ值在－８１‰～－５９‰之间变化。主要造岩矿物对保持氧同位素平衡分馏的样品，其Ｄ亏损主要受单阶段岩浆去气机理的制约。部分全岩样品表现出不同程度Ｄ－１８Ｏ同步亏损，这种亏损要受岩浆期后固相线下与外来渗透大气降水之间进行同位素交换机理的制约。石英δ１８Ｏ值基本正常，石英与碱性长石之间氧同位素不平衡分馏特征表明，苏州Ａ型花岗岩整体上起源于亏损１８Ｏ源区物质通过地球动力学再循环产生低δ１８Ｏ岩浆的可能性不大。根据氢氧同位素实测值和理论模型计算结果，推测苏州Ａ型花岗岩浆δＤ和δ１８Ｏ初始值分别为－５０±５‰和７．５±１．０‰，这排除了岩浆起源于曾经历过化学风化循环的地壳上部岩石的可能性。
Hydrogen and oxygen isotope studies are systematically carried out for the Suzhou A type granites The results show that the whole rock δ 18 O values are between +3 5‰ and +9 2‰, and their δ D range from -81‰ to -59‰ The D depleted samples with equilibrium oxygen isotope fractionations among rock forming mineral pairs are related to batch magmatic degassing process Some coupled D 18 O depleted whole rock samples impliy that the post magmatic subsolidus exchange with the external infiltrating meteoric water existed Quartz δ 18 O data show a normal distribution pattern, and there exists disequilibrium fractionation between quartz and feldspar Therefore, it is not possible that Suzhou A type granite is bulkly derived from low degree partial melting of the recycled 18 O depleted material According to theoretical modelling on the measured hydrogen and oxygen data, it is estimated that the Suzhou A type granitic magma initially has δD and δ 18 O of -50±5‰ and 7 5±1 0‰, respectively Thus,it is impossible to originate from chemically weathered rocks in the upper crust
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
1999年第2期224-236,共13页
Acta Petrologica Sinica
