Petrology and Geochemistry of the lawsonite (pseudomorph)-bearing eclogite in Yuka terrane, North Qaidam UHPM belt: An eclogite facies metamorphosed oceanic slice
Petrology and Geochemistry of the lawsonite (pseudomorph)-bearing eclogite in Yuka terrane, North Qaidam UHPM belt: An eclogite facies metamorphosed oceanic slice
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柴北缘尤卡地体超高压变质带含锂柱石（假象）榴辉岩的岩石学和地球化学：榴辉岩相变质洋片
DOI：
10.1016/j.gr.2016.10.011
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发表时间：
2017-02
影响因子：
6.1
通讯作者：
Liu Liang
中科院分区：
文献类型：
--
作者：
Ren Yunfei;Chen Danling;Kelsey D. E.;Gong Xiangkuan;Liu Liang
虽然硬毛钠榴辉岩被预测在俯冲带中的~ 45-300 km深度处是常见的，但它很少暴露在地球表面。在柴北缘超高压变质带的玉卡岩中发现了一种含硬铝石（假像）的榴辉岩。主要由石榴子石、角闪石、斜长石、石英、金红石等矿物组成，少量绿辉石残体和滑石。岩相学研究表明，石榴子石变斑晶中含有大量的长方形或菱形矿物集合体，由多晶单斜辉石或多相单斜辉石+钠云母±多硅白云母±石英和单斜辉石+角闪石±石英±富钠斜长石组成。这些集合体的特殊形态、矿物组合和重构成分表明它们是硬毛钠石之后的假像。相平衡模型预测，含硬铝石（赝象）榴辉岩经历了顺时针的P-T演化，峰值温度为570 °C，27 kbar，靠近石英-柯石英过渡边界。地球化学数据表明，硬铝石（假像）的榴辉岩具有类似MORB的亲和力与平坦的球粒陨石标准化稀土元素（REE）分布模式。锆石δ 18 O值（5.38 ± 0.10‰）与正常地幔（5.3 ± 0.3‰）相近，表明含硬毛石（假像）榴辉岩的原岩直接来自地幔岩，不受陆壳混染。含硬铝石榴辉岩的类MORB特征和锆石O同位素组成表明其原岩可能为洋壳片。西姆斯和LA-ICP-MS锆石U-Pb定年结果表明，该榴辉岩为436-438 Ma榴辉岩相变质年龄，与柴北缘超高压变质带的大陆俯冲年龄相似，但未获得其原岩年龄。这些数据表明，含硬铝石（假像）榴辉岩的原岩可能是Rodinia超大陆拼合过程中侵位于柴达木地块活动大陆边缘的一片元古宙洋壳，也可能是祁连洋与柴达木地块过渡带的早古生代洋壳。
Although lawsonite eclogite is predicted to be common at depth of ~ 45–300 km in subduction zones, it is rarely exposed at Earth's surface. In this study, we identified a lawsonite (pseudomorph)-bearing eclogite in Yuka terrane, North Qaidam UHPM belt. It is mainly composed of garnet, amphibole, clinozoisite, quartz and rutile with minor omphacite relics and talc. Petrographic investigation identified abundant rectangular- or rhombic- shaped mineral aggregates composed of polycrystalline clinozoisite or polyphase clinozoisite + paragonite ± phengite ± quartz and clinozoisite + amphibole ± quartz ± Na-rich plagioclase occurring in garnet porphyroblasts. The peculiar shape, mineral assemblages and reconstructed compositions of these aggregates show that they are pseudomorphs after lawsonite. Phase equilibrium modeling predicts that the lawsonite (pseudomorph)-bearing eclogite experienced a clockwise P–T evolution with a peak stage at 570 °C, 27 kbar, near the quartz–coesite transition boundary. Geochemical data show that the lawsonite (pseudomorph)-bearing eclogite has a MORB-like affinity with flat Chondrite–normalized rare earth element (REE) distribution patterns. Zircons from this sample have similar δ18O values (5.38 ± 0.10‰) with the normal mantle (5.3 ± 0.3‰), indicating that the protolith of the lawsonite (pseudomorph)-bearing eclogite is derived directly from mantle rock without continental crust contamination. The MORB-like character and zircon O isotopic composition of the lawsonite (pseudomorph)-bearing eclogite indicate that its protolith is likely to be an oceanic crustal slice. SIMS and LA–ICP–MS zircon U–Pb dating yielded a 436–438 Ma eclogite-facies metamorphic age for the lawsonite (pseudomorph)-bearing eclogite, similar to the continental subduction age of the North Qaidam UHPM belt, but did not obtain its protolith age. These data indicate that the protolith of the lawsonite (pseudomorph)-bearing eclogite may be either a piece of Proterozoic ocean that was emplaced in the active continental margin of the Qaidam block during the amalgamation of the Rodinia supercontinent, or the early Paleozoic oceanic crust in the transition zone between the Qilian Ocean and the Qaidam block.
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DOI：
--
发表时间：
2006
期刊：
--
影响因子：
--
作者：
Cheng Dan-ling
通讯作者：
Cheng Dan-ling
影响因子：
3.9
作者：
Shuguang Song;Lifei Zhang;Y. Niu;L. Su;B. Song;Dunyi Liu
通讯作者：
Shuguang Song;Lifei Zhang;Y. Niu;L. Su;B. Song;Dunyi Liu
影响因子：
5.3
作者：
Juliette F. Forneris;J. Holloway
通讯作者：
Juliette F. Forneris;J. Holloway
影响因子：
3.5
作者：
R. Orozbaev;T. Hirajima;A. Bakirov;A. Takasu;K. Maki;Kenta Yoshida;K. Sakiev;A. Bakirov;T. Hirata;M. Tagiri;A. Togonbaeva
通讯作者：
R. Orozbaev;T. Hirajima;A. Bakirov;A. Takasu;K. Maki;Kenta Yoshida;K. Sakiev;A. Bakirov;T. Hirata;M. Tagiri;A. Togonbaeva
影响因子：
3.4
作者：
C. Wei;Y. Li;Y. Yu;J. S. Zhang
通讯作者：
C. Wei;Y. Li;Y. Yu;J. S. Zhang