Font Size: a A A

Geological-geochemical Characteristics And Genesis Of Magmatic Rocks In Zhaojikou, Dongzhi, Anhui Province

Posted on:2014-03-08Degree:MasterType:Thesis
Country:ChinaCandidate:M HeFull Text:PDF
GTID:2250330401989165Subject:Mineralogy Petrology Gitology
Abstract/Summary:PDF Full Text Request
Zhaojikou Area is located in the southeast part of transitional areas of Yangtzesyneclise and Jiangnan landmass of Yangtze para-platform. Magmatism in this areais relatively weak, Daicun porphyry pluton is the only outcropped intrusive rocks,and acid dykes are well-developed. Based on the land and resources technologyproject “The Research of Metallization and Metallogenic Regularity of Pb-Zn-AuPolymetallic Ore in Zhaojikou Area of Dongzhi County, Anhui Province”, thispaper has made research into the Daicun porphyry pluton and acid dikes in therelated areas from the aspects of petrology, petrochemistry and petrologicalgeochemistry. It has also made comparison with the magmatic rocks in TongLingand Wannan areas to explore the features、metallogenic chronology and magmagenesis. Some Preliminary results have been made in this paper which are listed asfollowing:The researched region distributes granodiorite, granite-porphyry and diorite.The granite-porphyry outputs as a stock in Daicun, called as Daicun Rock Mass, theother two are dikes, distributing to NNE, NNW.Detailed zircon U-Pb dating of granodiorite and granite-porphyry samples givean age of146.4±0.92Ma and129.0±1.6Ma respectively. The granite-porphyrysamples in this research yields two intrusive time:140~150Ma and780~840Ma.The former is the formation age of the rocks, and the latter represents the formationage of source-rock which shows a large amount crust rocks had been melt in theformation process of magmatic rocks.The three types of rocks are calc-alkaline series chemically. The content ofSiO2in Daicun granodiorite, granite-porphyry and diorite was69.29%~70.13%,73.35%~79.97%and52.76%~56.46%respectively. They are peraluminousaccording to ACNK-ANK relation diagram. In SiO2-K2O relation diagram, most ofthe samples are calc-alkaline series rocks.The three types of rocks have similar characteristics of rare earth and traceelements, showing right-leaning curve of REE distribution patterns with slightlynegative Eu. The different is Σ REE is increased from granite-porphyry togranodiorite and then diorite. The trace element geochemical characteristics showlithophile elements(LILE)such as Ba, Rb and K, La, Ce are enriched in granodioriteand granite-porphyry, but compared with R, Th; Ba is depleted; and also have the geochemical features of negative anomaly in Nb, Ta, P and positive anomaly in Th,Zr, Hf, showing a similar characteristic with the granitic rocks in Tongling areagenerally.Sr-Nd-Pb isotope geochemistry characteristics show that the source materialsoriginated from the enriched lithosperic mantle, then generated from the mixingprocess of partial melting of crustal meterials.The magmatism of the plutons in research area may occurred under thegeodynamic setting of extrusion-extension translation stage, which is basically inaccordance with the geodynamic setting of adjacent area.
Keywords/Search Tags:magmatic rocks, geological and geochemical characteristics, petrogenic age, magma genesis, Zhaojikou, Dongzhi
PDF Full Text Request
Related items