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Characteristics And Petrogenesis Of The Mesozoic Intrusive Rocks In Fanchang, Anhui Province

Posted on:2006-05-14Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y E LouFull Text:PDF
GTID:1100360155951289Subject:Mineralogy, petrology, ore deposits
Abstract/Summary:PDF Full Text Request
The Fanchang area, located in northeastern Tongling City of Anhui Province, is a segment of the iron, copper, molybdenum and gold metallogenic belt in Middle and Lower Reaches of the Yangtse River. There occurs many Mesozoic magmatic intrusions. A petrographic, mineralogical, petrochemical and geochemical study combined with a field geological investigation has been conducted on these intrusions. Some important conclutions have been drawn based on the study and investigation.1. The lithologies of the intrusions in Fanchang area include biotite quartz monzonite,quartz diorite and granite, and the contents of SiO2 and K2O in these rocks are higher than those in intrusive rocks in the Tongling area. The rocks are K-rich alkaline granitoid.2. Some of the zircon grains from Binjiang granite and Banshiling biotite quartz monzonite intrusions yield 207Pb/206Pb ages of 124.3-125.3 Ma, while those from the intrusions in Tongling yield the ages of 135.5—139.5Ma. Evidently, the instrusions in Fanchang were formed over 10 Ma later than those in Tongling . Moreover, an inherited zircon sorted from granite in the Binjiang intrusion yields the age of 1049+ 29 Ma, indicating that it might be taken by an evolved magma from the oldest metamorphic basement to upper crust.3. The initial 87Sr/86Sr ratios of the samples from the Fanchang instrusions range from 0.707161 to 0.708312, and samples of K-feldspar from the Binjiang granite and Fenghuangshan granodiorite intrusions and ones of plagioclase from Shatanjiao granodiorite intrusion have a similar composition of Pb isotope. This supports derivation of these instrusions in the two areas from a mixing source of mantle and crust.4. The magmatic rocks from the intrusions in Fanchang and Tongling have similar REE distribution patterns with high value of Σ REE, enrichment of LREE and weak...
Keywords/Search Tags:intrusive rock, characteristics, petrogenesis, zircon SHRIMP dating, Mesozoic, Fanchang in Anhui
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