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Symplectite growth in the presence of alkaline fluids: evidence from high-aluminous metasediments of the Highland Complex, Sri Lanka

文献类型：期刊论文

作者Dharmapriya, P. L.6,7,8; Malaviarachchi, Sanjeewa P. K.7,8; Kriegsman, Leo M.5,6; Galli, Andrea4; Dyck, Brendan3; Sajeev, K.1; Su, Ben-Xun2; Pitawala, Amarasooriya7,8
刊名MINERALOGY AND PETROLOGY
出版日期2020-08-08
页码24
关键词Khondalite Symplectite Alkaline fluids Highland Complex Sri Lanka
ISSN号0930-0708
DOI10.1007/s00710-020-00710-2
英文摘要High-Al garnet-sillimanite-graphite gneisses (khondalites) from the Matale area in central Sri Lanka show evidence for open system formation of symplectites. Three types of khondalite (type A, B, and C) were collected from two localities (Lo(1)and Lo(2)) in this area. In Lo(1), khondalite type A shows a stable mineral assemblage with garnet (Grt), ribbon quartz (Qtz), prismatic sillimanite (Sil), alkali feldspar (Akfs) and minor graphite. The abundant leucosome is interpreted as (modified) crystallised melt (Liq). Qtz is invariably rimmed by Akfs double corona. In type B, Grt and Sil are partially rimmed by spinel (Spl)-Akfs symplectites. Type C samples show the extensive development of Spl-Akfs symplectites, locally with Bt, as well as corundum (Crn)-Akfs symplectites after Sil in domains relatively remote from Grt. Mineral inclusions in Grt suggest advanced biotite dehydration melting producing Grt +/- Spl + Liq, similar to other Sri Lankan metapelitic granulites. PeakP-Tconditions are similar to 8-9 kbar and similar to 850 degrees C. The symplectites developed on the retrograde path, with Ti in Bt thermometry indicating 700-720 degrees C. The chemical potential calculations indicated that the chemical potential gradient from garnet to sillimanite could well have produced the AKfs+Spl symplectite. Hence the most critical point is the initiation of Grt breakdown reactions which can facilitate the formation of Spl + Akfs and Crn + Akfs symplectites after sillimanite via the chemical potential gradient. Textural observations coupled with mass balance of symplectitic reaction textures indicate that addition of external Na and K to reaction sites is needed to trigger the symplectite formation. Excess Fe and Mg from Grt breakdown probably diffused away from garnet along a chemical potential gradient. As a result, Sil in the vicinity of Grt has broken down to Spl-Akfs symplectites, whereas Sil further away from Grt produced Crn-Akfs symplectites. Spl-Akfs and Crn-Akfs symplectites after Grt and Sil in khondalites are restricted to the boundary zone between the Wanni and Highland Complexes. The formation of symplectites is inferred to have taken place during or just after a decompression stage with minor cooling, under the influence of an alkaline fluid derived from nearby pegmatites, when the assemblage Grt + Sil was already metastable. The combination of fluids and symplectites indicates a very fast process rate.
WOS关键词ULTRAHIGH-TEMPERATURE METAMORPHISM ; SPINEL PLUS QUARTZ ; MINERAL EQUILIBRIA CALCULATIONS ; HIGH-GRADE ORTHOGNEISSES ; U-PB GEOCHRONOLOGY ; IVREA-VERBANO ZONE ; STRONA-DI-OMEGNA ; REACTION TEXTURES ; MIXING PROPERTIES ; BUSHVELD COMPLEX
资助项目National Research Council (NRC) of Sri Lanka[11-180] ; Ministry of Technology and Research[MTR/TRD/AGR/3/1/04] ; Naturalis Biodiversity Center, Leiden, Netherlands ; Stichting Dr. Schurmannfonds[88/2012] ; Stichting Dr. Schurmannfonds[94/2013] ; Stichting Dr. Schurmannfonds[101/2014]
WOS研究方向Geochemistry & Geophysics ; Mineralogy
语种英语
WOS记录号WOS:000557331300001
出版者SPRINGER WIEN
资助机构National Research Council (NRC) of Sri Lanka ; National Research Council (NRC) of Sri Lanka ; Ministry of Technology and Research ; Ministry of Technology and Research ; Naturalis Biodiversity Center, Leiden, Netherlands ; Naturalis Biodiversity Center, Leiden, Netherlands ; Stichting Dr. Schurmannfonds ; Stichting Dr. Schurmannfonds ; National Research Council (NRC) of Sri Lanka ; National Research Council (NRC) of Sri Lanka ; Ministry of Technology and Research ; Ministry of Technology and Research ; Naturalis Biodiversity Center, Leiden, Netherlands ; Naturalis Biodiversity Center, Leiden, Netherlands ; Stichting Dr. Schurmannfonds ; Stichting Dr. Schurmannfonds ; National Research Council (NRC) of Sri Lanka ; National Research Council (NRC) of Sri Lanka ; Ministry of Technology and Research ; Ministry of Technology and Research ; Naturalis Biodiversity Center, Leiden, Netherlands ; Naturalis Biodiversity Center, Leiden, Netherlands ; Stichting Dr. Schurmannfonds ; Stichting Dr. Schurmannfonds ; National Research Council (NRC) of Sri Lanka ; National Research Council (NRC) of Sri Lanka ; Ministry of Technology and Research ; Ministry of Technology and Research ; Naturalis Biodiversity Center, Leiden, Netherlands ; Naturalis Biodiversity Center, Leiden, Netherlands ; Stichting Dr. Schurmannfonds ; Stichting Dr. Schurmannfonds
源URL[http://ir.iggcas.ac.cn/handle/132A11/97610]  
专题地质与地球物理研究所_中国科学院矿产资源研究重点实验室
通讯作者Dharmapriya, P. L.
作者单位1.Indian Inst Sci, Ctr Earth Sci, Bangalore 560012, Karnataka, India
2.Chinese Acad Sci, Key Lab Mineral Resources, Inst Geol & Geophys, Beijing 100029, Peoples R China
3.Simon Fraser Univ, Dept Earth Sci, Burnaby, BC V5A 1S6, Canada
4.Swiss Fed Inst Technol, Dept Earth Sci, Sonnegstr 5, CH-8092 Zurich, Switzerland
5.Univ Utrecht, Dept Earth Sci, NL-3584 CB Utrecht, Netherlands
6.Nat Biodivers Ctr, Dept Res & Educ, Darwinweg 2, NL-2333 CR Leiden, Netherlands
7.Univ Peradeniya, Fac Sci, Dept Geol, Peradeniya 20400, Sri Lanka
8.Univ Peradeniya, Postgrad Inst Sci, Peradeniya 20400, Sri Lanka
推荐引用方式
GB/T 7714		 Dharmapriya, P. L.,Malaviarachchi, Sanjeewa P. K.,Kriegsman, Leo M.,et al. Symplectite growth in the presence of alkaline fluids: evidence from high-aluminous metasediments of the Highland Complex, Sri Lanka[J]. MINERALOGY AND PETROLOGY,2020:24.
APA Dharmapriya, P. L..,Malaviarachchi, Sanjeewa P. K..,Kriegsman, Leo M..,Galli, Andrea.,Dyck, Brendan.,...&Pitawala, Amarasooriya.(2020).Symplectite growth in the presence of alkaline fluids: evidence from high-aluminous metasediments of the Highland Complex, Sri Lanka.MINERALOGY AND PETROLOGY,24.
MLA Dharmapriya, P. L.,et al."Symplectite growth in the presence of alkaline fluids: evidence from high-aluminous metasediments of the Highland Complex, Sri Lanka".MINERALOGY AND PETROLOGY (2020):24.

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