| 广西大厂锡多金属矿床硅质岩和层状矿体氧硅同位素研究 |
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| 关键词:silicon isotope oxygen isotope Dachang |
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| SILICON AND OXYGEN STABLE ISOTOPE STUDIES ON THE SILICEOUS ROCKS AND STRATIFORM ORE BODIES OF THE DACHANG TIN POLYMETALLIC DEPOSIT,GUANGXI |
| The Dachang tin polymetallic deposit in the middle sector of the Danchi polymetallic mineral zoneis located in the southwest margin of the Jiangnan ax is,It occures in a flyschoid sedimentary strtawhich consists of carbonate rock,siliceous rock and fine clastic rock of the Middie-Uppor Devoninian. Asone of the largest tin ore deposits in China, it has been the subject of intensive researches over the pastyears,However several questions on the origin of the Dachang deposit remain to be selved,In particu-lar,little is known about the siliceous rock、the host rock of the ore.and the silicon seurce in the ore.A study on silicon and oxygen isotopes for siliceous rocks and ore from the Dachang deposit wasconducted to provide information on the source of silicon,An additional object of this paper was to e-valuate potentional applications of silicon isotopic analyses,in study of ore genesis;The siliceous rock is an important pert of sedimentary facies of the Late Devonian sedimentarystrata in Guangxi Province,It is about 60-70 m thick in the mine area and composed mainly ofquartzs,There are two kinds of structure for siliceous reeks,the massive structure and the laminatedstructure,The quartz samples from the mine are area show a δ￣(30)Si range of 0.2‰ to 0.8‰,and aδ￣(18)O range of 12.0‰to 21.3‰.Theirδ￣(30)Si valuee seem different to the general exhalative reeks(-3.1‰)to 0‰),the biotite granite in Longxianggai((-0.3‰to-0.2‰)and diorite porphyTitein Dachang(-0.1‰).In fact,the range of silicon isotopes is very similar to that of the shallow ma-rine radiolarite, Theee hish δ￣(30)Si values of the siliceous reek combining to the dlscovery of the radiolar-ia trace in this area show that the siliceous rock in mine area forms by biogenic activity and their sili-con may come from the reeks of continental crust and scawater and may have experiened a long termevolution and fractionation before precipitation. The stratiform orebodies consist of interbeded sulphides and siliceous bands, The siliceous bands have δ￣(30)Si valuee of一0.6‰ to 0.6‰ and δ￣(18)O values of 13.2‰ to 15.9‰;the sulphides bands have δ￣(30)Si values of-0.4‰to 0.3‰and δ￣(18)O values of 14.6‰to l6.0‰.These results show that their Si may come from more than one source. Beside of biogenic Si sediments some Si may come fromclastic sediment of exhalative fluids.The δ￣(18)O valueal of the siliceous rock and ore bodies are relatively lower than those of normal cor-respondent rocks,It reflects the influence of oxygen isotope exchang with Iater hydrothermal fluids. |
| YAO Xiao-mei,DING Ti-ping.1994.SILICON AND OXYGEN STABLE ISOTOPE STUDIES ON THE SILICEOUS ROCKS AND STRATIFORM ORE BODIES OF THE DACHANG TIN POLYMETALLIC DEPOSIT,GUANGXI[J].Acta Geoscientica Sinica,15(1,2):124-130. |
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