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| 1 | 古亚洲洋碳酸盐俯冲再循环及其对华北克拉通岩石圈组成的影响显示文摘在洋盆闭合的长期演化历史中,沉积碳酸盐在板块俯冲作用中会被不同程度地带入地球内部,从而显著影响岩石圈地幔性质和大尺度气候变化.那些经历了俯冲带深部循环作用的碳酸盐(岩)是记录已消失洋盆的重要载体.华北克拉通北缘汉诺坝玄武岩中的碳酸岩侵入体记录了灰岩再循环进入地幔后熔融形成碳酸岩过程的岩石学和地球化学特征,并且携带了大量碎屑锆石.这些碎屑锆石具有从前寒武纪到显生宙的年龄谱,但前寒武纪年龄峰(包括~2.5Ga、2.1~2.3Ga、1.8~2.0Ga、~1.65Ga、1.3~1.4Ga、~1.1Ga、0.91~0.94Ga、0.74~0.81Ga和0.62~0.63Ga)完全不同于华北克拉通北缘地质体中的锆石年龄谱,而与兴蒙造山带沉积物中碎屑锆石的年龄谱相似.尤其是300~373Ma锆石显著偏正的ε_(Hf(t))值(7.7~13.5)明显区别于同时期华北克拉通北部的锆石,而与兴蒙造山带中锆石的正ε_(Hf(t))值一致.上述特征表明,汉诺坝碳酸岩侵入体的灰岩源岩来自古亚洲洋,而且灰岩沉积时间不早于300Ma,也就是说古亚洲洋在晚石炭世-早二叠世还未完全闭合.中亚造山带中广泛分布的变质碳酸盐和华北克拉通北缘普遍出现的岩石圈地幔碳酸盐交代作用表明古亚洲洋曾发育了广泛的沉积碳酸盐岩,而且很大一部分可能在俯冲过程中返回了地球内部,并显著影响了华北克拉通北缘岩石圈的组成和物理化学性质(如氧逸度). | 刘勇胜 陈春飞 何德涛 张拉 虞凯章 | 2021 | 中国科学:地球科学2021，51，10： | 1 |
| 2 | Recycling of Paleo-Asian Ocean carbonates and its influence on the lithospheric composition of the North China Craton显示文摘The deep carbon cycle,which plays a critical role in mantle evolution and Earth habitability,is closely linked to the recycling of carbonate-bearing rocks through subduction.Marine carbonates are subducted to different depths during the closure of oceanic basins,thus carry important signatures of the disappeared oceanic basins.Petrological and geochemical features of the Hannuoba carbonatites in the northern North China Craton indicate that they were formed by melting of limestone subducted to mantle depths.Here,we show that detrital zircons carried by these carbonatites have a broad spectrum of U-Pb ages from Precambrian to Phanerozoic.Precambrian age peaks are at~2.5 Ga,2.1–2.3 Ga,1.8–2.0 Ga,~1.65 Ga,1.3–1.4 Ga,~1.1 Ga,0.91–0.94 Ga,0.74–0.81 Ga,and 0.62–0.63 Ga,respectively.The recorded age peaks are different from those in the northern North China Craton and thus preclude an origin of crustal contamination.Nevertheless,the Precambrian age spectra are compatible with those of the Xingmeng Orogen in the southeastern Central Asian Orogenic Belt.Furthermore,the significantly positiveεHf(t)values of 7.7–13.5 for the 300–373 Ma zircons are similar to those in the Xingmeng Orogen but different from those in the northern North China Craton.All these features suggest that the limestone precursor for the Hannuoba carbonatites was originated from the Paleo-Asian Ocean,and its deposition time was not earlier than 300 Ma.This indicates that the PaleoAsian Ocean still existed in the late Carboniferous to early Permian.The widespread distribution of metamorphic carbonates in the Central Asian Orogenic Belt indicates that there may have been widespread sedimentary carbonates in the Paleo-Asian Ocean.A large amount of sedimentary carbonates was probably carried into mantle during subduction of the Paleo-Asian oceanic slab,which significantly modified the chemical and physical properties of the lithospheric mantle. | Yongsheng LIU Chunfei CHEN Detao HE La ZHANG Kaizhang YU | 2021 | Science China Earth Sciences2021，64，8： | 0 |
| 3 | 南秦岭地块紫阳地区早古生代岩石圈伸展规律、动力学机制及基性岩墙成因显示文摘南秦岭地块紫阳地区广泛出露早古生代基性岩墙群,其研究具有重要的地球动力学意义。虽然如此,已有相关研究目前主要集中于志留纪基性岩墙群方面,而对早古生代(如,寒武纪、奥陶纪)基性岩墙群的研究仍相对薄弱。从而制约了对南秦岭早古生代岩石圈伸展过程相关问题(如,时空分布规律、地幔性质、动力学机制和相关成矿作用)的总体把握。鉴于尚存的科学问题,本研究选取康家坪、梨树梁、大竹坪、清明寨、苟家山、庙梁上、曾家山和毛坝村的基性岩墙群为研究对象,开展了矿物学、岩石学、锆石U-Pb年代学、地球化学和Sr-Nd-Hf同位素方面的研究,对其精细时代格局、成因及成岩动力学背景进行了系统探讨。研究结果显示,紫阳早古生代基性岩墙以辉绿岩和辉绿玢岩为主,形成时代为奥陶纪(478.8-486Ma),属碱性系列岩石(K_(2)O+Na_(2)O变化范围为4.10%-5.14%)。另外,基性岩墙群具有富集LREE、Rb、Ba、Sr、Nb、Ta、Zr、Hf和Eu(Eu/Eu*=1.13-1.35),亏损HREE、U、Pb和Ti的典型地球化学特征。(87Sr/86Sr)i=0.7044-0.7050、εNd(t)=3.1-3.6、εHf(t)=4.4-12.1,176Hf/177Hf=0.282634-0.282846,暗示基性岩墙为地幔柱作用过程亏损岩石圈或软流圈地幔部分熔融作用的产物。另外,在辉绿岩成岩过程经历了橄榄石和单斜辉石的分离结晶,但地壳混染的影响不明显。 | 刘燊 冯彩霞 陈晓青 赵慧博 徐静妍 范焱 | 2023 | 岩石学报2023，39，3： | 0 |
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