A review and appraisal on the study progress of the geological evolution of Sri Lanka: Rock associations, metamorphism and their relations with Gondwana
文献类型：期刊论文
| 作者 | Malaviarachchi, Sanjeewa Prabhath Kumara2; Dharmapriya, Prasanna Lakshitha2; Zhao Lei1; Zhang YanBin1; Zhai MingGuo1 |
| 刊名 | ACTA PETROLOGICA SINICA
 |
| 出版日期 | 2021-05-01 |
| 卷号 | 37期号:5页码:1287-1320 |
| 关键词 | Sri Lanka Granulite Ultrahigh temperature metamorphism Geochronology Gondwana |
| ISSN号 | 1000-0569 |
| DOI | 10.18654/1000-0569/2021.05.01 |
| 英文摘要 | Changes in our Earth's environment and biota are usually closely associated with tectonic processes. The assembly of the supercontinent Gondwana during Neoproterozoic-Cambrian is synchronous with some of these critical changes. The East African Orogen (ca. 650 620Ma) and the Kuunga Orogen (ca. 600 500Ma) are two major orogenic events that welded major parts of Gondwana and they cross each other in Sri Lanka. A thorough understanding of the evolutionary history of Sri Lanka is, therefore, of great importance for the reconstruction of Supercontinent Gondwana and the proper interpretation of the tectonic processes involved. The Precambrian crystalline basement of Sri Lanka has been divided into four parts according to metamorphic grade and isotopic features of constituent rock assemblages, which are the Wanni, Kadugannawa, Highland and Vijayan complexes. The Highland Complex situating in the middle part of Sri Lanka hosts the oldest rocks (ca. 2000 1800Ma) of Sri Lanka and its basement rocks often display granulite facies metamorphism. Rocks of the other three terranes in Sri Lanka are relatively younger (ca. 1100 700Ma) and their metamorphic grade is also relatively lower than that of the Highland Complex, at amphibolite-granulite facies. High-grade metamorphism of these terranes occurred during Neoproterozoic-Cambrian (ca. 610 500Ma) is a prominent feature which was accompanied by pervasive anatexis. This tectonothermal event in Sri Lanka is relatively younger than those developed in East African Orogen (ca. 650 620Ma) and largely synchronous with the Kuunga Orogen (ca. 600 500Ma), which is inconsistent with the previously proposed interpretation that the Mozambique Suture (East African Orogen) passes through Sri Lanka. Besides, it is still unclear whether the high-grade metamorphism in Sri Lanka is the result of one orogenic event or that of multiple orogenic events. High- to ultrahigh-temperature metamorphism is a typical feature of basement rocks in the Highland Complex of Sri Lanka. Ultrahigh temperature (UHT) granulites contain diagnostic mineral assemblages of sapphirine + quartz and/or high-Al orthopyroxene + sillimanite, and A1203 contents of orthopyroxene grains reach up to 13%. Peak metamorphic temperature conditions of these UHT granulites have been suggested to range from 950 C to 1150 C, and peak pressure conditions range from 10kbar to 16kbar, with most of them exhibiting clockwise P-T paths. White-eye socket around garnet grains and consisting of Opx + PI and/or Amp + PI and/or Cpx + PI can be usually seen in mafic granulites which occur only in the middle and eastern parts of the Highland Complex. These reaction textures indicate isothermal decompression P-T evolution patterns and relatively fast uplifting rates of granulites after peak metamorphism from lower crustal levels. Charnockite is a major rock type across Sri Lanka and it could be seen accompanying almost all other high-grade rocks, like pelitic granulites, mafic granulites, and so on. The charnockites in Sri Lanka are quite complex and the oldest part of them have protolith ages of Paleoproterozoic (1850Ma) or even Archean, although age constraints of them are poor. Some charnockites have protolith ages of ca. 1100 750Ma, geochemical compositions of which resemble those of calc-alkaline arc magmatic rocks, and they also exhibit high-grade metamorphism during ca. 580-500Ma. Besides, some charnockites are synchronous with regional granulite facies metamorphism during ca. 580-550Ma. Incipient charnockites can also be observed to occur as dark patches within gneissic rocks whose consisting minerals indicate amphibolite facies metamorphism. Most researchers believe that these incipient charnockites post-date regional granulite facies metamorphism. The differences in rock assemblage, metamorphic grade, and geochronological framework between the four terranes of Sri Lanka have been widely accepted, which imply that they have distinct evolutionary histories. However, whether the assembly of Sri Lanka is related with the closure of Mozambique Ocean, and exactly how Kuunga Orogen influenced basement rocks of Sri Lanka, are still issues of debate? This paper reviews study progresses on major lithologies of different terranes, high to ultrahigh temperature metamorphism, metamorphic geochronology of Sri Lanka, and the role Sri Lanka played in Gondwana. Based on these reviews, we propose that issues like the tectonic framework of basement rocks in Sri Lanka, Neoproterozoic-Cambrian high- to ultrahigh temperature metamorphism, petrogenesis of charnockites, geochronological framework, the geological significance of Sri Lanka in the reconstruction of Gondwana, are all under debate and worthy of further studies. |
| WOS关键词 | ULTRAHIGH-TEMPERATURE METAMORPHISM ; HIGHLAND COMPLEX ; GRANULITES ; AGES |
| WOS研究方向 | Geology |
| 语种 | 英语 |
| WOS记录号 | WOS:000664449300001 |
| 出版者 | SCIENCE PRESS |
| 源URL | [http://ir.iggcas.ac.cn/handle/132A11/101967]  |
| 专题 | 地质与地球物理研究所_岩石圈演化国家重点实验室 |
| 通讯作者 | Zhao Lei |
| 作者单位 | 1.Chinese Acad Sci, Inst Geol & Geophys, State Key Lab Lithospher Evolut, Beijing 100029, Peoples R China 2.Univ Peradeniya, Fac Sci, Dept Geol, Kandy 20400, Sri Lanka |
| 推荐引用方式 GB/T 7714 | Malaviarachchi, Sanjeewa Prabhath Kumara,Dharmapriya, Prasanna Lakshitha,Zhao Lei,et al. A review and appraisal on the study progress of the geological evolution of Sri Lanka: Rock associations, metamorphism and their relations with Gondwana[J]. ACTA PETROLOGICA SINICA,2021,37(5):1287-1320. |
| APA | Malaviarachchi, Sanjeewa Prabhath Kumara,Dharmapriya, Prasanna Lakshitha,Zhao Lei,Zhang YanBin,&Zhai MingGuo.(2021).A review and appraisal on the study progress of the geological evolution of Sri Lanka: Rock associations, metamorphism and their relations with Gondwana.ACTA PETROLOGICA SINICA,37(5),1287-1320. |
| MLA | Malaviarachchi, Sanjeewa Prabhath Kumara,et al."A review and appraisal on the study progress of the geological evolution of Sri Lanka: Rock associations, metamorphism and their relations with Gondwana".ACTA PETROLOGICA SINICA 37.5(2021):1287-1320. |
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来源：地质与地球物理研究所
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