摘要
岚山头含柯石英榴辉岩呈透镜状构造块体产于晚元古代含霓石碱长花岗质片麻岩中，其原岩为玄武岩浆分离结晶晚期堆积的辉长岩。该榴辉岩典型的共生矿物组合可划分为4个世代：①Cpx1＋Mu1（OrPhen1）＋Qz＋Pl1；②Cpx2（Om1）＋Gr1＋Ky＋Cs；③Cpx3（Om2）＋Gr2＋Phen2＋Ky＋Zo＋Qz；④Pl2＋Tl＋Mrg＋Phen3＋Czo＋Qz。它们分别反映4个变质演化阶段：前榴辉岩相阶段（M1）、柯石英榴辉岩相阶段（M2）、后榴辉岩相第一退变质阶段（M3）及后榴辉岩相第二退变质阶段（M4）。各阶段的变质条件；M1为P≤1．56Gpa，T＝700℃；M2为P＝2．74～2．95GPa，T＝722℃～981℃；M3为P＝1．34～1．54GPa，T＝568℃～589℃；M4为P＝0.61～1．04GPa，T469℃。柯石英榴辉岩相阶段（M2）末期的年龄为613．3±30．4Ma，榴辉岩相第二退变质阶段（M4）的多硅白云母40Ar－39Ar坪年龄为313．49Ma。据上述资料再塑了一个较完整的顺时针PTt轨迹。
Coesite-bearing eclogites which occur as lens were formed in the Neoproterozoic aegirine-bearing alkaline feldspar gneiss,Its protolith is gabbro formed in the late stage of basalt lavas fractional crystallization. The typical paragenetic mineral assemblages can be divided into four generations: ①Cpx1+Mu1 (Orphen1 ); ②CPx2 (Om1 ) + Gr1 + Ky + Cs; ③ CPx3 (Om2 ) + Gr2 + Phen2 + Ky + Zo + Qz; ① Pl2 + T1 + Mrg + Phen3 + Cz0 + Qz. They reflect four metamorphic evolution stages, respectively; prc-eclogite-facies stage (M1); coesite-eclogite-factes stage (M2); the first retrogressive metamorphic stage of post eclogite-factes(M3); the second retrogressive metamorphic stage of post-eclogite-facies (M4). The metamorphic conditions of these stages are: P≤1. 56Gpa and T700℃ for M1; P ＞2. 74- 2. 95GPa and T 722-981℃ for M2; P 1.34-1. 54GPa and T568-598℃for M3; and P 0. 61-1. 04GPa and T469℃ for M4 The age of late stage coesite-eclogite factes (M2)is 613. 3±30. 4Ma, and the 40Ar/39Ar age of phengite for the second stage of eclogite-factes(Mr) is 313. 49Ma. According to the above information,a nearly complete clockwise PTt path has been set up.
出处
《山东地质》
1997年第1期23-39,共17页
Geology of Shandong
