Petrogenesis of Garnet in the Darongshan-Shiwandashan Granitic Suite of the South China Block and the Metamorphism of the Granulite Enclave
详细信息
- 责任者：Jiao Shujuan (State Key Laboratory of Lithospheric Evolution ; Institute of Geology and Geophysics ; Chinese Academy of Sciences ; Beijing 100029 ; China) ; Guo Jinghui
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(5)
- 关键词：石榴子石岩 ; garnetite ; 麻粒岩 ; granulite ; 华南地区 ; South China
- 页码：p.1740-1758
- 图表：illus., 7 tables, 57 refs.
- 分类号：0802
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
Garnets from the Jiuzhou granitic pluton of the Darongshan-Shiwandashan suite have been distinguished into four types based on their different textural and chemical characteristics: magmatic,peritectic,residual / metamorphic grains,and the transform from peritectic to magmatic that confirms the dissolution-precipitation process. Two types of granulite enclaves are divided based on their different microdomainal mineral assemblages. Recognition of microdomainal mineral assemblages,determination of metamorphic stages,and reaction analyses,combined mineral chemistry with phase equilibria modeling are performed to constrain thermal evolution of the two types of granulite enclave in granite. The original conditions of the granulite enclaves are 800 ～ 830℃ and 7. 2 ～ 8. 0kbar, which is representative of the garnet-bearing assemblage,reflecting the late stage of the partial melting in the source. Opx + Crd reaction rim around garnet or biotite might be coeval with crystallization of cordierite,and formed at conditions of 810 ～ 860℃ and 4. 6 ～ 5. 2kbar. Further decompression results in the formation of Spl + Crd association at 850℃ and 3. 1 ～ 3. 8kbar. In combination of the obtained data,a clockwise P-T path is retrieved and characteristic of decompression associated with slightly heating and succedent isobaric cooling in response to ascent and emplacement of the host granitic magma. This study coupled with the available geochronological data from previous researches suggests that the petrogenesis of both granite and its granulite enclave is related to the anatexis of the crust during 250 ～ 260Ma,and might have been provided with heat source by the coeval Emeishan mantle plume.
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