| 世界上最古老的沉积海泡石矿床——华北中元古代沉积海泡石矿 |
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| 关键词:Middle Proterozoic sedimentary sepiolite deposit the Northern China |
| 基金项目:本项目同时还得到国家自然科学基金资助 |
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| The Location and Genesis of the Northern China Middle Proterozoic Sepiolite Deposit——the World Oldest Sedimentary Sepiloite Deposit |
| The Northern China Middle Proterozoic sedimentary sepiolite is distributed 60-180 km to the east of Beijing. The ore-bearing Wumaishan Formation of Jixian System (1310-1207 Ma by Ar-Ar method) has thickness from 2000m to more than 3000 m with well developed sedimentary rhythm, consisting mainly of dolostone and delostone with sil-ica band. At the base of rhythm is the sandy clayish dolostone, sedimentary characteristics of which represent a still water low energy environment. The texture of platty pebble of chrysanthemum type, widely developed in rhythm, is a quasi-synchronous texture by syn-chronous fracture. The development to a large extent of this and other sliding textures in-dicates the frequent activity of synchronous fracture, resulting in alteration of depth of sea water in basin and syclic introduction of landsource sand and clay, finally the extremely thick rhythmic sedimentation of Wumishan Formation. According to our study sepiloite was formed at the late stage of transition period from Yanliao rift to platform. The miner-alization area is located in lagune near the Shanhaiguan paleocontinent side.
The basal layer of rhythm in Wumaishan Formation is clay-bearing layer, in which se-piolite montmorillonite and illite are the main clay mineral. The thickness of ore body, the content of sepiolite and landsource(silty)sand are decreasing as the distance from paleo-continent is increasing.
Although after sedimentation the sepiolite has evolved a long 1200 Ma year geological history, the ore body is preserved perfectly, not changed into talc in great amount. Com-pared with other deposits and home and abroad Northern China Middle Proteozoic sepiolite deposit is distinguished by its ancient age of ore-forming process, speciality of mineraliza-tion and perfect preservation and is the world oldest particular sedimentary sepiolite de-posit. |
| Huang Xueguang,He Yuzhen,Wang Yalie,Zang Guangcai,Jiang Wentian.1996.The Location and Genesis of the Northern China Middle Proterozoic Sepiolite Deposit——the World Oldest Sedimentary Sepiloite Deposit[J].Acta Geoscientica Sinica,17(z1):36-42. |
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