胶东海阳所堆积辉长岩的变质反应结构、石榴石形成及P-T演化  

Corona Texture, Garnet Formation and P-T Evolution of Gabbroic Cumulate from Haiyangsuo Area Eastern Shandong Province, China

作　　者：倪志耀[1] 王仁民[2] 袁建平[2] 

机构地区：[1]中国科学院地质与地球物理研究所,北京100029 [2]北京大学地质学系,北京100871

出　　处：《高校地质学报》2001年第3期316-328,共13页Geological Journal of China Universities

基　　金：国家自然科学基金项目 (4 9872 0 6 5 );高等学校博士学科点专项科研基金项目 (96 0 0 0 12 1);北京大学分析测试基金项目资助

摘　　要：海阳所堆积辉长岩由橄长岩、橄榄辉长岩和辉长岩组成。在橄长岩和橄榄辉长岩中发育有典型的变质反应结构 :主要为橄榄石与斜长石之间形成由斜方辉石、尖晶石、角闪石和石榴石等矿物组成的多期次次变边 ,并有三个不同世代变质矿物 ,早期Cpx +Opx +Spl,中期Amp ,晚期Grt ;其次是钛铁矿与斜长石之间形成石榴石次变边 ,相对比较简单 ,只有一个世代变质矿物 ,为Grt+Amp +Rut或Grt+Rut。岩石中石榴石是通过斜长石与角闪石或斜长石与钛铁矿之间的变质反应形成的 ,虽为峰值变质作用的产物 ,但变质反应的期次及类型不同导致了所形成石榴石的温度和压力有所不同。堆积辉长岩形成演化的温压计算表明 ,堆积辉长岩在经过近等压降温的岩浆作用之后的变质作用早期 ,仍为近等压降温 ,而晚期则表现为近等温升压。这一特殊的PThe granite gneiss of the Late Proterozoic Jinning stage is the main exposed rock in Haiyangsuo area, eastern Shandong Province, China. There are some lenses and structural blocks of ultramafic rocks (serpentinite), metamorphic gabbro, plagioclase amphibolite and metamorphic silicalite with varying dimensions and proportions in the granite gneiss. The strong deformation and metamorphism took place in these structural blocks, but the Yaodao accumulative gabbros, that formed through the mineral accumulation under the low pressure and isobaric cooling condition, have the distinct gabbro texture and rhythmic structure, and consist of troctolite, olivine gabbro and amphibole gabbro. Multistage metamorphic reaction textures were preserved in the troctolite and olivine gabbro. There are two different mineral assemblages for the corona texture in the accumulative gabbros. The one is between plagioclase and olivine. It contains the mineral assemblage of orthopyroxene, spinel, amphibole and garnet; The another is between plagioclase and ilmenite. It is only in the olivine gabbro. The mineral asemblage is more simple and contains garnet, amphibole and rutile or garnet and rutile. The former may be divided into three generations on the basis of petrographic evidence. The early mineral assemblage is characterized by orthopyroxene, clinopyroxene and spinel that formed through a reaction between olivine and plagioclase at temperature of about 760℃-876℃ and pressure of 0.44-0.60GPa; the intermediate mineral assemblage is marked by appearance of tschermakite and disappearance of clinopyroxene via the reaction between plagioclase and clinopyroxene subsequently at temperature of about 660℃-700℃ and pressure of 0.40- 0.50 GPa; the late mineral assemblage is characterized by formation of garnet and pargasite or pargasitic hornblende resulted from the reaction between tschermakite and plagioclase at temperature of 650℃-660℃ and pressure of 0.83-0.92 GPa. The latter is only one generation and marked by the fo

关 键 词：堆积辉长岩 变质反应结构 石榴石 P-T演化 矿物组合 橄长岩 辉长岩 

分 类 号：P588.3[天文地球—岩石学]