Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

Zhen-Sheng Li ¹, De-Liang Liu ², Xiao-Yong yang ³, Xiao-Qi Wu ², Ying Tan ⁴, Bai-Chang Wang ⁵

Affiliations
1 School of Resources and Environmental Engineering, Hefei University of Technology, Hefei 230009, CN
2 School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, CN
3 School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, IN
4 Institute of Geologic Survey of Jiangsu Province, Nanjing 210018, CN
5 Exploration Department, Daqing Oilfield Company Ltd, PetroChina, Daqing 163453, CN

Abstract

Based on studies of major element, rare earth element, fluid inclusion and absorbed gas, the possible source matters of carbon dioxide (CO₂) and their potentialities to form gas accumulations in deep northern Songliao basin, NE China were addressed in this paper. Mantle-Derived magma, volcanic rocks, carbonate rocks and organlc matters are four kinds of potentia1 source matters, whose significances are degressive in turn and vertical distributions could be divlded into shallow, middle, deep and deeper levels. In shallow level, the source matters of CO₂ are volcanic rocks and carbonation rocks with higher total carbon contents and absorbed CO₂ contents, 0 24%-7 76% and 0 213%-1 387% respectively. The absorbed CO₂ contents of volcanic rocks are negatively correlated wlth the S₁O₂ contents, and positively with the Na₂O+K₂O contents. The principal source matters are metamorphic carbonate rocks in middle level and mantle-Derived magma in deep and deeper levels. Higher CO₂ abundance in magmatic systems correspondng to deep volcanic rocks could be suggested by characteristics of lithogeochemistry and fluid inclusion as well as tectonic setting. The volcanic rocks of Yingcheng Formation and corresponding magmatic activities are the most favorable CO₂ source matters in northern Songliao Basin.

Keywords

Carbon Dioxide, Source Matters, Volcanic Rock, Northern Songliao Basin.

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Xiao-Yong Yang ¹, Jing Huang ¹, Kui-Ren Wang ¹

Affiliations
1 CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University Science and Technology of China, Hefer 230026, CN

Abstract

Yangtze valley is one of the most important metallogenic regions in the Jurassic-Cretaceous penod in East Asian continent, where more than 200 polymetallic Cu-Fe-Au and Mo, Zn, Pb, Ag deposits are documented Cu-Au deposits in Anhui Province (Lower part of Yangtze) are the most important among these deposits. Data of chemical compositions of trace elements were collected from literature for Yanshanian (Mesozoic) igneous rocks which have close relationship with the Cu-Au mineralization. The Cu -Au mineralization in middle to lower Yangtze valley can be divided into three types mainly skarn type, porphyry type and volcanic type. In this paper, the details of trace and rare earth elements from Shaxi, Anqing, Chuxian, Tongling and Luzong Cu-Au bearing deposits are dealt with in detail Rocks in the localities of Shaxi, Chuxian and Anqing intrusives have almost similar REE distribution patterns which show little assimilation with the wall rocks during the formation of Cu-Au deposits. However, the REE distribution patterns in Tongling skarn deposit are different altogether when compared to the other Cu-Au related rocks adjacent to areas of Mesozoic intrusives. This might have resulted due mainly to the volatile transport or assimilation of some elements producing complex patterns of trace element distributions superimposed on effects caused by crystal/melt equilibra. The trace element distribution shows that the mantle compatible elements such as Sc, Cr, Co and Ni and some transitional compatible elements such as Ti, V, Mn, Fe and Cu have strongly fractionated compared to the average contents of trace elements of crustal rocks, especially those of Cu, with very largely positive anomaly. This could be interpreted as an important crustal-mantle interaction during the Yanshania (Mesozoic) period when the multiple Cu-Au mineralization formed in the Yangtze metallogenic belt in China. The lithophile elements such as K,Rb, Th, Sr, Ba, Li and La are also enriched compared to the average contents of the crustal rocks, reflecting the regional geochemical anomalies of these elements and may be interpreted as an important reason of Cu-Au mineralization in this region.

Keywords

Cu-Au Deposits, Trace and REE Elements, Jurassic-Cretaceous, Yangtze metallogenic, Province, Anhui, Eastern China.

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Xiao-Yong Yang ¹, Xue-Ming Yang ², Lai-Li Jiang ³, Kuiren Wang ¹, Li-Guang Sun ¹

Affiliations
1 school of Earth and Space Sciences, Advanced Center for Earth Sciences and Astronomy of the Third World Academy of Sciences, University Science and Technology of China, Hefei 230026, CN
2 Department of Geology, University of New Brunswick, Fredericton, NB, E3B 5A3, CA
3 Anhui Academy of Geology and Survey, Hefei 230001, CN

Abstract

Shaxi porphyry Cu-Au deposit in central Anhui Province is located in the Middle-Lower reaches of Yangtze metallogenic valley in east China. Red sandstone and conglomerate of Cretaceous age, clastic rocks of Middle and Lower Jurassic, clastic rocks of continental sea facies of Upper Devonian-Middle Silurian age, various continental volcanic rocks of Jurassic age form the rock types of the Shaxi porphyry copper-Gold metallogenic belt. The ore district is cut by multiple faults, of which the most important are Tanlu fault and Fanshan-Tongling faults, the former being the largest fault system in East Astan continent and the later being the regional deep fault. The geological, geochemical and mineralogical methods used to investigate the porphyry copper-Gold deposit associated with large scale sulphide mineralizatlon forms the theme of this paper. Through field geological surveys, mineralogical observation, compositional analyses on minerals using EPMA, geochemical analyses on Cu-Au-Bearing intrusive rocks, fluid inclusion and oxygen, hydrogen, sulphur isotopic studies, and element distributions detected by PIXE system, the characteristics of mineralization and gold occurrence in the Shaxi porphyry copper-Gold deposit have been fully investigated. The results of the study form the basis for further research and exploration on the porphyry copper-Gold deposit of the Middle-Lower Yangtze region.

Keywords

Porphyry Gold Deposit, Geochemistry, Fluid Inclusion, Stable Isotope Studies, Tan-Lu Fault, Shaxi Cu-Au Deposit, Anhui Province, East China.

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