| 苏鲁构造杂岩带乳山地区（石榴）斜长角闪岩P-T演化轨迹及其地质意义——来自岩石学、矿物化学及相平衡模拟的约束 |
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| 引用本文： | 朱浩忠,田忠华,王泽利,向华,张书凯.苏鲁构造杂岩带乳山地区（石榴）斜长角闪岩P-T演化轨迹及其地质意义——来自岩石学、矿物化学及相平衡模拟的约束[J].地球科学,2020,45(9):3420-3435. |
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| 作者姓名： | 朱浩忠 田忠华 王泽利 向华 张书凯 |
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| 作者单位： | 1.山东科技大学地球科学与工程学院, 山东青岛 266000 |
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| 基金项目： | 中国地质调查局地调项目DD20190003国家自然科学基金项目41672191国家自然科学基金项目41972205江西省教育厅科学技术研究重点项目GJJ190586 |
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| 摘 要： | 大量来自于华北陆块的高压变质岩被发现发育于苏鲁构造杂岩带中，给俯冲带上盘物质如何卷入陆-陆俯冲碰撞作用的研究带来新的契机.通过对乳山地区（含榴）斜长角闪岩进行岩石学、矿物化学及相平衡模拟的研究，发现其保留有3个不同变质演化阶段的矿物组合，峰前矿物组合为粗粒石榴子石+斜长石+角闪石+石英+钛铁矿；峰期矿物组合由石榴子石+单斜辉石+斜长石+角闪石+石英+钛铁矿组成，为典型高角闪岩相矿物组合；峰后退变质阶段矿物组合为角闪石+斜长石+石英+石榴子石+钛铁矿，发育有典型的“白眼圈”结构.相平衡模拟与温压计算表明，乳山午极石榴斜长角闪岩峰前变质阶段的P-T条件分别为P=6.4~7.0 kbar、T=610~640℃，表明其俯冲至30 km左右的地壳深度；峰期变质阶段P-T条件分别为P=9.3~10.0 kbar、T=700~730℃，表明其已俯冲至36~40 km的地壳深度，峰后退变质阶段P-T条件分别为P=5.2~5.8 kbar、T=680~710℃.锆石U-Pb定年结果表明乳山午极石榴斜长角闪岩原岩时代为1 734±24 Ma，龙角山水库斜长角闪岩变质时代为1 849±28 Ma，研究表明二者均来源于华北构造岩片.结合前人研究资料，推测乳山地区石榴斜长角闪岩原岩可能经历三叠纪俯冲作用并发生变质；其与杂岩带中来自华南的构造岩片发生混杂，共同构成华北-华南板块间宽约80~100 km的构造杂岩带.
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| 关 键 词： | 苏鲁构造杂岩带 石榴斜长角闪岩 P-T轨迹 锆石U-Pb定年 相平衡模拟 岩石学 |
| 收稿时间： | 2020-04-06 |
(Garnet Bearing) Plagioclase Amphibolite P-T Evolution Path and Its Geological Implications in Rushan Region,Sulu Tectonic Complex: Constraints by Petrology,Mineral Chemistry and Phase Equilibria Modeling |
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| Abstract: | Many high-pressure metamorphic rocks or blocks from the North China Craton were recognized in the Sulu tectonic complex belt, providing many opportunities to investigate the mechanism of the involvement and exhumation of the materials from the upper subduction zone. In this paper, we present a study of petrology, mineral chemistry and phase equilibria modeling on the (garnet) plagioclase amphibolites in the Rushan area, and three metamorphic stages have been found in the rock: (1) The pre-peak stage with the mineral assemblage of garnet+quartz+plagioclase+amphibole+ilmenite; (2) the peak high-pressure stage with the diagnostic amphibolite-facies assemblage of garnet+clinopyroxene+plagioclase+amphibole+quartz+ilmenite; (3) the post-peak decompression stage represented by amphibole+plagioclase+garnet+ilmenite, and typical "white eye" textures can be observed. Phase equilibria modeling constrained the P-T conditions of the pre-peak, peak, and post-peak of 6.4－7.0 kbar/610－640 ℃, 9.3－10.0 kbar/700－730 ℃, 5.2－5.8 kbar/680－710 ℃, respectively. These P-T conditions indicate that the materials from the upper subduction zone have already subducted to ~30 km and 36－40 km, respectively. U-Pb dating of zircons show that the protolith age of the garnet plagioclase amphibolite is 1 734±24 Ma, and the metamorphic age of plagioclase amphibolite is 1 849±28 Ma (from Longjiaoshan reservoir), which all indicates a North China Plate origin. Our data, combined with those of previous studies, indicate that the Wuji garnet plagioclase amphibolites might have been involved in the subduction in Triassic and experienced metamorphism. Together with the "tectonic rock slices" from South China Block, a 80－100 km wide tectonic mélange zone is suggested between the North China Plate and the South China Block. |
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