青藏东缘六合—香多镁铁质深源包体的平衡P-T条件及其指示意义  

EQUILIBRIUM P-T CONDITIONS OF MAFIC DEEP-DERIVED ENCLAVES AND ITS SIGNIFICANCE IN LIUHE-XIANGDUO AREA OF EASTERN TIBET

作　　者：魏启荣[1] 王江海[2] 

机构地区：[1]中国地质大学材料科学与化学工程学院,湖北武汉430074 [2]中国科学院广州地球化学研究所,广东广州510640

出　　处：《地球科学进展》2004年第5期722-731,共10页Advances in Earth Science

基　　金：国家重点基础研究发展规划项目"大陆碰撞过程中壳幔物质能量交换及冈底斯带成矿背景评估"(编号:G1998040807);中国博士后科学基金项目"三江中段扬子与冈瓦纳陆块间地球化学边界的研究"资助

摘　　要：依据青藏东缘六合—香多镁铁质深源包体中石榴石、辉石、角闪石和斜长石的矿物电子探针成分,采用Grt Cpx温度计(TEG79、TP85、TK88、和TR2000)、Grt Hbl温度计(TGP84和TRV2000)和Hbl Pl温度计(TBH90)以及角闪石Al压力计(PAl in Hbl)估算了包体的平衡温压条件。结果表明,石榴透辉岩、石榴斜长角闪岩、石榴角闪岩、斜长角闪岩和角闪石岩包体的平衡温压分别是770～920℃和0.83～1.50GPa(相当于27～50km深)、730～950℃和0.85～1.04GPa(相当于28～34km深)、720～900℃和0.74～1.32GPa(相当于24～44km深)、512～753℃和0.71～0.98GPa(相当于23～32km深)以及0.60～0.84GPa(相当于20～28km深)。前3类包体主要来自下地壳,平衡温压较高(720～950℃、0.74～1.50GPa);后2类包体主要来自中地壳,平衡温压较低(510～735℃、0.60～0.98GPa)。包体的平衡温压条件还暗示了高钾岩浆起源的最小深度在50km以上。Based on electron microprobe analyses of garnets, pyroxenes, amphiboles and plagioclases from mafic deep-derived enclaves in Liuhe-Xiangduo area, eastern Tibet, calculated equilibrium temperatures of the enclaves by Grt-Cpx geothermometers (T(EG79), T(P85),T(K88), and T(R2000)), Grt-Hblgeothermometers (T(GP84)and T(RV2000)), and Hbl-Plgeothermometers (T(BH90)), and equilibrium pressures by aluminum-in-amphibole geobarometrys (P(Al-in-Hbl)). The results showed that equilibrium temperatureand pressureconditions of garnet diopsidite, garnet amphibolite, garnet hornblendite, amphiboliteand hornblenditewere 770～920 ℃ and 0.83～1.50 GPa (equivalent to27～50 km depth), 730～950 ℃ and 0.85～1.04 GPa (28～34 km), 720～900 ℃ and 0.74～1.32 GPa (24～44 km), 512～753 ℃ and 0.71～0.98 GPa (23～32 km), and 0.60～0.84 GPa (20～28 km). The P-T conditions in the enclaves revealed the former three types of enclaves came from low-crust with higher P-T (720～950 ℃ and 0.74～1.50 GPa), and the latter two derived from middle-crust with lower P-T ( 510～735 ℃ and 0.60～0.98 GPa). The P-Tconditionof enclaves still indicated the source depth of the high-K magma is 50km at least.

关 键 词：青藏东缘 六合-香多 镁铁质深源包体 平衡温压 

分 类 号：P58[天文地球—岩石学] P59[天文地球—地质学]