江苏东海榴辉岩相变质脉体的流体包裹体研究  

A study of fluid inclusions in the eclogite-facies metamorphic veins in Donghai,Jiangsu Province,eastern China.

作　　者：沈昆 张泽明[2] 石超[2] 王金丽[2] 

机构地区：[1]山东省地质科学实验研究院,济南250013 [2]中国地质科学院地质研究所,北京100037

出　　处：《岩石学报》2008年第9期1987-2002,共16页Acta Petrologica Sinica

基　　金：国家重点基础研究发展项日(973计划)(2003CB716501);国家自然科学基金重大项目(40399142和40472036)资助

摘　　要：苏鲁超高压变质带南部的东海地区产出大量榴辉岩体,其中存在含蓝晶石—黝帘石/褐帘石—绿辉石—金红石(+磷灰石+锆石)石英脉,它们含有与榴辉岩主岩相近似的矿物组合,故应该是在与榴辉岩相近的超高压 P-T 条件下形成的。这些脉体的褐帘石/黝帘石和金红石具有很高的稀土元素(REE)和高场强元素(HFSE)含量及变化的 Sr、Ba、V 和 Cr 含量。脉体的蓝晶石,特别是褐帘石和黝帘石含有丰富的固体与流体包裹体,包括:(1)多相固体包裹体(multiphase solidinclusions,Ⅰ型);(2)多子晶流体包裹体(multidaughter mineral-bearing fluid inclusions,Ⅱ型);(3)H_2O-CO_2包裹体(Ⅲ型);(4)高盐度盐水包裹体(Ⅳ型);和(5)中-低盐度 H_2O 包裹体(Ⅴ型)。Ⅰ型和Ⅲ型包裹体主要存在于蓝晶石中,偶尔见于黝帘石中,呈孤立分布或沿晶内裂隙分布;Ⅱ型包裹体多沿褐帘石和黝帘石晶核密集或随机分布,或沿晶内裂隙分布;Ⅳ型和Ⅴ型包裹体多见于石英中,也见于褐帘石和黝帘石中,一般沿裂隙分布。能谱和激光拉曼探针分析表明Ⅰ型包裹体中的固相有钠云母、刚玉、方解石、菱铁矿、硬石膏、重晶石、磁铁矿和黄铁矿,以及未知相;Ⅱ型包裹体中的固相有白(钠)云母、硬石膏、方解石、磷灰石、天青石、磁铁矿和黄铁矿,以及未知含水硅酸盐等;Ⅲ型包裹体主要含 H_2O 和 CO_2;Ⅳ型包裹体除含 H_2O 液相外,常见固相有石盐、方解石和不透明矿物,而气相有时可含明显数量的 CO_2和 N_2。显微测温显示,多数Ⅱ型包裹体的冰点(T_(mi))在-5℃～0℃,相应的盐度为0～7.86%NaCl equiv.。鉴于Ⅱ型包裹体含有多种子矿物,根据包裹体中固体总合量并结合溶解度资料估计,Ⅱa和Ⅱb型包裹体中溶质浓度可分别达到40%～70%和25%～40%,原始流体可能属于 Na^+-Ca^(2+)(Sr^(2+))-Mg^(2+)-Fe^(2+)-CO_3^(2-)-SO_4~2-SiO_3^(2-)±PO_4^(3-)-Cl^--H_2O 体系。Ⅳ型包裹体中 COKyanite-zoisite/allanite-omphacite-rutile （ ± apatite ± zircon） quartz veins occur in the Chizhuang eclogite in the Donghai area, in the southern part of the Sulu ultrahigh-pressure （UHP） metamorphic belt. These veins consist of mineral assemblages similar to their host eclogite and thus are considered be formed under P-T conditions similar to their host. Abundant solid/fluid inclusions are found in kyanite （Ky） and allanite/zoisite （Aln/Zo） ; they include： （ 1 ） multiphase solid inclusions （ type Ⅰ ） ; （2） muhidanghter mineral-bearing fluid inclusions （ type Ⅱ ） ; （3） H2O-CO2 inclusions （ type Ⅲ ） ; （4） high-salinity brine inclusions （ type Ⅳ ） and （5） medium-low salinity aqueous inclusions （ type Ⅴ ）. Types Ⅰ and Ⅲ inclusions are found mainly in Ky and rarely in Zo, occurring as isolated ones or along intragranular fractures whereas type Ⅱ inclusions occur densely/randomly in the cores of Aln/Zo or along intragranular fractures; types Ⅳ and Ⅴ inclusions occur commonly along fractures in quartz and also in Aln/Zo. EDS and Raman analyses indicate that the type Ⅰ inclusions have a daughter mineral association of paragonite ± corundum ± magnetite ± anhydrite ± barite ± calcite/siderite ± pyrite, plus unknown phase （ s ）, whereas type Ⅱ inclusions contain paragonite （ muscovite ）, anhydrite, calcite, apatite, celestite, magnetite, marcasite and unknown hydrosilicate （s）. Type m inclusions contain mainly H2O and CO2 without other volatile components in the CO2 phase while type Ⅳ inclusions contain halite ± calcite ± opaque in addition to a liquid （ H2 O） and a vapor phase which sometimes contains significant amount of CO2 and N2. Microthermometric measurements show that the final melting temperature of ice in most type Ⅱ inclusions ranges from - 5 to 0℃ which correspond to salinity values of 0 - 7.86% NaCL equivalent. Since type Ⅱ inclusions contain solid phases the concentrations of total solutes in ty

关 键 词：江苏 东海县 榴辉岩 高压脉体 流体包裹体 UHP 

分 类 号：P588.348[天文地球—岩石学]