Lithospheric modification by carbonatitic to alkaline melts and deep carbon cycle: Insights from peridotite xenoliths of eastern China
Lithospheric modification by carbonatitic to alkaline melts and deep carbon cycle: Insights from peridotite xenoliths of eastern China
复制标题
碳酸盐岩向碱性熔体的岩石圈改造和深层碳循环：来自中国东部橄榄岩捕虏体的见解
DOI：
10.1016/j.lithos.2020.105789
复制
发表时间：
2020-12
期刊：
影响因子：
3.5
通讯作者：
Guangfu Chen
中科院分区：
文献类型：
--
作者：
Lixu Deng;Xianlei Geng;Yongsheng Liu;Keqing Zong;Lüyun Zhu;Zhengwei Liang;Zhaochu Hu;Guodong Zhang;Guangfu Chen
俯冲洋壳板片中的碳酸盐岩可以在板片脱水后继续存在并转移到深部地幔中。这种深碳循环在生成碳酸盐质至碱性熔体中起着关键作用。然而，这一过程是否以及如何影响岩石圈地幔仍然是个谜。针对这些问题，本文对中国东部长乐中新世玄武岩中的两种地幔捕虏体（一种为韦尔岩，一种为含熔穴橄榄岩）进行了详细的岩相学、原位化学和Sr同位素研究。昌乐二辉橄榄岩中含有碳酸盐熔融包裹体和磷灰石，仅相对于昌乐二辉橄榄岩富集单斜辉石。单斜辉石的特征在于高的（La/Yb）N（4.7-41）和低的Ti/Eu（873-2292）比率，并且与碳酸盐硅酸盐熔融状组合物平衡。这些岩石学和化学特征表明，韦尔岩是由橄榄岩和碳酸盐硅酸盐熔体反应形成的。另一方面，昌乐含熔体袋橄榄岩被认为是由富含角闪石纯橄榄岩的角闪石就地熔融/破裂产生的。低橄榄石Fo（~89）、高（La/Yb）N（~50）和低Ti/Eu（~1070）的角闪石的存在表明，这种富角闪石纯橄榄岩可能是由橄榄岩与碳酸盐地幔中的含水碱性玄武岩熔体反应形成的。结合前人对长乐二辉橄榄岩捕虏体的研究结果，揭示了碳酸盐岩-碱性熔体对碳酸盐地幔源区的一系列地幔交代作用。伟尔岩和二辉橄榄岩中单斜辉石的~（87）Sr/~（86）Sr比值一直很高（高达0.7036），表明地幔源区的碳酸盐组分来自地幔过渡带内停滞的太平洋板块。这一研究为探讨俯冲洋板深部碳循环在陆内岩石圈地幔化学改性中的作用提供了新的视角。
Carbonates in subducting oceanic slabs can survive beyond slab dehydration and be transferred into the deep mantle. Such deep carbon cycling plays a critical role in generating carbonatitic to alkaline melts. However, whether and how this process has influenced the lithospheric mantle still remains enigmatic. To address these issues, here we provide a detailed petrographic, in-situ chemical and Sr isotopic study on two mantle xenoliths (a wehrlite and a melt pocket-bearing peridotite) entrained by the Changle Miocene basalts from the eastern China. The Changle wehrlite contains carbonate melt inclusions and apatites and is merely enriched in clinopyroxene relative to the Changle lherzolites. The clinopyroxenes are characterized by high (La/Yb)N(4.7–41) and low Ti/Eu (873–2292) ratios and equilibrated with carbonated silicate melt-like compositions. These petrographic and chemical features indicate that the wehrlite was formed by reaction between peridotite and carbonated silicate melts. On the other hand, the Changle melt pocket-bearing peridotite is suggested to have been produced by in-situ melting/breakdown of amphiboles of an amphibole-rich dunite. Low olivine Fo (~89), presence of amphiboles with high (La/Yb)N(~50) and low Ti/Eu (~1070) ratios suggest that such amphibole-rich dunite would have been formed by reaction of peridotite with hydrous alkaline basaltic melts from a carbonated mantle. Our data, combined with previously reported data of the Changle lherzolite xenoliths, unravel a series of mantle metasomatisms by carbonatitic to alkaline melts from carbonated mantle sources. The consistently high87Sr/86Sr ratios (up to 0.7036) of the clinopyroxenes in both the wehrlites and lherzolites indicate the carbonate components in the mantle sources were derived from the stagnant Pacific slab within the Mantle Transition Zone. This study provides a fresh perspective on the role of deep carbon cycling from subducted oceanic slabs in chemical modification of intracontinental lithospheric mantle through reaction with different types of melts.
登录
查看更多内容
影响因子：
3.5
作者：
E. Bali;A. Zanetti;C. Szabó;D. Peate;T. Waight
通讯作者：
E. Bali;A. Zanetti;C. Szabó;D. Peate;T. Waight
影响因子：
3.9
作者：
D. Draper;T. Green
通讯作者：
D. Draper;T. Green
影响因子：
5.3
作者：
Liu, Xin;Zhao, Dapeng;Wei, Wei
通讯作者：
Wei, Wei
影响因子：
--
作者：
F. Su;Yan Xiao;Huaiyu He;B. Su;Ying Wang;R. Zhu
通讯作者：
F. Su;Yan Xiao;Huaiyu He;B. Su;Ying Wang;R. Zhu
影响因子：
3.9
作者：
Gerbode, Christine;Dasgupta, Rajdeep
通讯作者：
Dasgupta, Rajdeep