Metamorphic PT path, U-Pb zircon dating and tectonic implications of High-pressure Pelitic Granulites from the Kharta region, Southern Tibet, China
Metamorphic PT path, U-Pb zircon dating and tectonic implications of High-pressure Pelitic Granulites from the Kharta region, Southern Tibet, China
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藏南喀尔塔地区高压泥质麻粒岩变质PT路径、U-Pb锆石定年及其构造意义
DOI：
10.1016/j.gr.2021.07.006
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发表时间：
2021-07
影响因子：
6.1
通讯作者：
Zhang Lifei
中科院分区：
文献类型：
--
作者：
Li Qing-Yun;Zhang Lifei
在喜马拉雅山中部的Thongmön地区发现了与Kharta片麻岩中榴辉岩共生的HP泥质麻粒岩，它对喜马拉雅造山带的构造演化提供了重要的制约。在泥质麻粒岩（DR 15 P15）中鉴定出三代石榴石。第一代石榴石是自形到半形变斑晶的核心部分（Grt-I核心），随后是加热阶段Grt-I地幔的生长。第三代石榴石的代表是薄边的Grt-I和小颗粒（Grt-II）的矩阵，这可能是成核和生长的反应，在折返过程中的围生反应。岩石学证据和P-T假剖面计算揭示了四期变质演化：1）以Grt-I核及其矿物包裹体金红石、钛铁矿和石英为代表的俯冲变质阶段（M1），变质条件为740-760 °C和13-16 kbar; 2）近等压加热阶段，稍减压至高压麻粒岩相（M2，820-840 °C，13-14 kbar），反映在Grt-I地幔成分和金红石Zr含量的增加; 3）加热减压阶段（M3），由Grt-I边缘钙铝榴石含量的减少和较高的XAnin斜长石支持，在硅线石稳定场中产生T > 860 °C和P = 10-11 kbar; 4）最终减压阶段，随后冷却（M4，T ~ 800 °C和P = 6-8 kbar），这由黑云母取代硅线石和基质中黑云母中较低的Ti含量指示。根据锆石微量元素地球化学、锆石包裹体和石榴石与锆石的稀土配分特征，变质锆石边可能生长于中中新世（16-13 Ma）的麻粒岩相阶段（M3）的Grt-I边/Grt-II形成期。Kharta片麻岩中泥质麻粒岩的P-T史表明，在14-13 Ma之前，由于STDS的活动，它们被俯冲到亚洲板块之下，并被折返到中下地壳深度。
HP pelitic granulites associated with eclogites from the Kharta Gneiss are found in the Thongmön area, central Himalaya, which provides significant constraints for the tectonic evolution of the Himalayan orogeny. Three generations of garnets are identified in pelitic granulites (DR15P15). The first generation of garnet is core sections of euhedral to subhedral porphyroblasts (Grt-I core) followed by growth of Grt-I mantle during the heating stage. The third generation of garnet is represented by thin rims of Grt-I and small grains (Grt-II) in the matrix, which likely nucleated and grew in response to peritectic reaction during exhumation. Petrographic evidence andP–Tpseudosection calculation reveal a four-stages metamorphic evolution: 1) a prograde metamorphic stage (M1) represented by Grt-I core and its mineral inclusions rutile, ilmenite and quartz with metamorphic conditions of 740–760 °C and 13–16 kbar; 2) a near isobaric heating stage with slightly decompression to HP granulite-facies (M2, 820–840 °C, 13–14 kbar) indicated by the composition of Grt-I mantle and the increase of Zr concentrations of rutile in it; 3) a heating decompression stage (M3) supported by a decrease in grossular content in the Grt-I rim and higher XAnin plagioclase, yielding T > 860 °C and P = 10–11 kbar in the sillimanite stability field; 4) a final decompression stage followed by cooling (M4, T ~ 800 °C and P = 6–8 kbar) indicated by biotite replacing sillimanite and lower Ti content in biotite in the matrix. Based on the zircon trace element geochemistry, zircon inclusions, and the REE partitioning between garnet and zircon, the metamorphic zircon rims with middle Miocene age (16–13 Ma) probably grew during Grt-I rim/Grt-II formation at granulite facies stage (M3). TheP–Thistory of the pelitic granulites of the Kharta Gneiss indicates that they were subducted beneath the Asian plate and exhumed to middle-lower crustal depths prior to 14–13 Ma due to the activity of STDS.
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影响因子：
5.3
作者：
M. Konrad‐Schmolke;T. Zack;P. O'Brien;Dorrit E. Jacob-
通讯作者：
M. Konrad‐Schmolke;T. Zack;P. O'Brien;Dorrit E. Jacob-
影响因子：
2.9
作者：
J. Chakungal;J. Dostal;D. Grujic;S. Duchêne;K. S. Ghalley
通讯作者：
J. Chakungal;J. Dostal;D. Grujic;S. Duchêne;K. S. Ghalley
影响因子：
5.3
作者：
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通讯作者：
P. Leloup;G. Mahéo;N. Arnaud;E. Kali;E. Boutonnet;Dunyi Liu;Xiaohan Liu;Haibing Li
影响因子：
3.9
作者：
Groppo, Chiara;Rolfo, Franco;Indares, Aphrodite
通讯作者：
Indares, Aphrodite
影响因子：
5
作者：
D. Rubatto;J. Hermann
通讯作者：
D. Rubatto;J. Hermann