The Characteristics, Origin and Tectonic Setting of Presinian Spilite-keratophyre Series in Xichangcentral Yunnan Region
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    Abstract:

    The Presinian spilite-keratophyre series in Xichang-central Yunnan renion is confined mostly to the Dahongshan and Hekou nroups, In regional tectonics it sca- tteredly exposed on the both sides of Anninghe-Yimen deep fracture. The spilite- keratophyre series is closely associated with comcagmatic volcanics or hypabyssal intrusions including albite gabbro-diabase, albitophyre and quartz alhitophyre. The keratophyre represented by alhitc granulite from the jiangyi-Pintan for- mation of Hehou group has a zircon U一Pb age of 1.725Ga, the enigmatic gneiss in the Dibadu formatioan, which is wer-laid by Dalzongshan croup, yields a Rb-Sr age of 1.706Ga, and the remant mirimatic gneiss in Iiangding group, a crystalline ba- sement in this region, gives zirco UL-Pb ages from 2.061 to 2.951Ga Threrfore, Dahongshan and Hehou groups would have age from 1.7 to 2Ga. The spilite-kera- tophyre series is petrochemically similar to those in the other parties of the world,except for having higher Na20 (6-8wt%),Fe2O3+Fe0 and TiO2 and lower K2O, Mg0 and Ca0 contents, According to the Wrigh1 alkalinity coefficient, the spilite- keratophyre in this region should be belonged to the subalkalic rock series. The presence of remained magmatic flowage structure, felsophyric and spheru- litic textures in the rocks, absence of replacement remnant of intermediate and ba- sic plagioclase in the albite and consitence of composition of Na2O in the rocKS indicate that the spilite-keratophyre in this region is neither metasomatogenic nor metamorphogenic but rather the magmatogenic rock resulted from the crystallization of intermediate-basic magma enriched in Na and H2O, The sampler from the spilite-keratophyre are plotted to the field A in the logτ-lonσ diagram .On the basic of the rocl; associa`ion and some field critera, The spilite-keratophyre should be considered to be an eruptive-sedimentary in a bathyal environment.

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申屠保勇,1989,西昌─滇中地区前震旦纪细碧一角斑岩系特征,成因及产出环境[J].岩石矿物学杂志,8(4):321~330.,1989,The Characteristics, Origin and Tectonic Setting of Presinian Spilite-keratophyre Series in Xichangcentral Yunnan Region[J]. Acta Petrologica et Mineralogica,8(4):321~330.

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