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Last Paleozoic Subduction in Eastern Junggar: Evidence from Geochemistry, Geochronology and Petrogenesis of Carboniferous Volcanic Rocks
Feng Zhang,
Tao Xu,
Yingchuan Lu
Issue:
Volume 11, Issue 6, December 2022
Pages:
338-354
Received:
13 May 2022
Accepted:
30 May 2022
Published:
4 November 2022
DOI:
10.11648/j.earth.20221106.11
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Abstract: The Carboniferous Batamayineishan volcanic rocks in Eastern Junggar are widely distributed on a huge scale. Studies on geochemistry, geochronology and petrogenesis of these volcanic rocks show that: (1) they have complex volcanic rock types with basalt - andesite - dacite - rhyolite assemblages and are of high-K calc-alkaline series, with enrichment of large ion lithophile elements (LILE) (Sr, K, Rb, Ba, Th) and light rare earth elements (LREE) and depletion of high field strength elements (HFSE) (Nb, Ta, Ti) and heavy rare earth elements (HREE). Besides, the initial 87Sr/86Sr and 143Nd/144Nd ratios are low and the εNd (t) values mostly vary from 3.0 to 6.2. All these features suggest that the volcanic rocks were formed in the immature back-arc basin related to subduction; (2) The Batamayineishan volcanic rocks may be produced by the multi-source materials interaction of young lower crust and deep mantle materials which are mainly composed of the Paleozoic residual oceanic crust and island arc system. The basalts were dominantly derived from the depleted mantle, and the crust-mantle magmatism and the homogenization of the Sm-Nd isotope system have occurred with a small amount of young crustal materials in the magma source. Their formation is likely related to the partial melting of the overlying mantle wedges caused by the fluids generated by the metamorphism and dehydration of subducted sediments and/or subducted oceanic crust. However, the acidic volcanic rocks are the result of the mixing of a small amount of mantle-derived magma undergoing strong crystallization differentiation and a mass of crust-derived materials; (3) The Sm-Nd isochron age of the basalts is (319.7±5.9) Ma, which is consistent with the regional tectonic setting and the evidence from fossils in Batamayineishan Formation, and represents the eruption age of the Batamayineishan volcanic rocks. In summary, we consider that the subduction of the Paleo-Asian Ocean continued in Eastern Junggar around 320Ma, and its final closure time should be between 320 Ma and 310 Ma. During this process, the volcanic magmatisms in Eastern Junggar were very intense and involved abundant mantle-derived materials, implying that Eastern Junggar has a superior prospecting potential.
Abstract: The Carboniferous Batamayineishan volcanic rocks in Eastern Junggar are widely distributed on a huge scale. Studies on geochemistry, geochronology and petrogenesis of these volcanic rocks show that: (1) they have complex volcanic rock types with basalt - andesite - dacite - rhyolite assemblages and are of high-K calc-alkaline series, with enrichmen...
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The Hydrothermal Alteration Activity Related to the Orogenic Lode-Gold at Kplessou, Toumodi, Cote d’Ivoire
Zie Ouattara,
Gnamba Franck Emmanuel Gouedji,
Aristide Ghislain Beugre Dago,
Aya Anne Flora Koffi,
Allialy Marc Ephrem,
Yacouba Coulibaly
Issue:
Volume 11, Issue 6, December 2022
Pages:
355-363
Received:
7 October 2022
Accepted:
25 October 2022
Published:
4 November 2022
DOI:
10.11648/j.earth.20221106.12
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Abstract: The southern part of the Fettèkro greenstone is known to host orogenic gold deposits. It is the case of Kpléssou in the region of Toumodi where gold has been mined since colonial times, in the 1900s, from its auriferous quartz plus calcite veins. Therefore, this gold potential has attracted the artisanal and small gold miners. The objective of this study is to highlight the characteristics of the geological formations and their mineralization from the distal to the proximal zone in order to deeply undertand the associated hydrothermal alteration footprints. In the fulfillment of this objective, field work has been undertaken at Kpléssou then followed by discussion with artisanal miners to elucidate the gold hosts and favorable structures. This step has been used to sample three mineralization zones: distal, intermediate and proximal. These samples served as the basis for the laboratory work realized at the University of Man. Petrographically, we notice the basalts, sericitoschist and various shales impregnated by the aurifeous veins of quartz and carbonates. The basalt and sericitoschist have undergone a ductile deformation resulting to their folding and schistosity and a brittle deformation which forms the veins. A strong hydrothermal alteration has affected the lithologies: sericitisation, chloritisation, carbonatation and sulphidation. Gold mineralization is epigenetic in the basalt, post-magmatic and is associated with sulphides lining the quartz + ankerite veins. However in the sericitochist where sulphides are disseminated, the mineralization is admitted as syngenetic, synmetamorphic and prekinematic. This mineralization in Kpléssou shows that it is an orogenic lode-gold type.
Abstract: The southern part of the Fettèkro greenstone is known to host orogenic gold deposits. It is the case of Kpléssou in the region of Toumodi where gold has been mined since colonial times, in the 1900s, from its auriferous quartz plus calcite veins. Therefore, this gold potential has attracted the artisanal and small gold miners. The objective of this...
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Integrated Geophysical Investigation to Delineate Deep Structural Features - A Case Study from the Eastern Part of Junggar Basin, NW China
Issue:
Volume 11, Issue 6, December 2022
Pages:
364-373
Received:
17 October 2022
Accepted:
2 November 2022
Published:
11 November 2022
DOI:
10.11648/j.earth.20221106.13
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Abstract: In order to study the features of geophysical field and deep structure of the eastern part of Junggar basin, we collected gravity and magnetic data with a scale of 1:1,000,000. Then, we calculated the isostatic gravity anomaly based on the Bouguer gravity anomaly data and the aeromagnetic anomaly by reduction to the pole (RTP) based on the aeromagnetic anomaly data, separated the gravity anomalies and the magnetic anomalies using the filtering method and the wavelet transform method, and obtained the regional gravity and magnetic anomalies and the multi-order wavelet transform approximation of gravity and magnetic anomalies. Combined with existing geological and geophysical research, we analyzed the features of the gravity anomalies and the magnetic anomalies, and discussed the deep structure of the eastern part of Junggar basin. The results showed that the upper mantle uplift in the eastern part of Junggar basin. The Junggar basin turned down under the northern Tianshan orogenic belt and the eastern Junggar orogenic belt. The regional high gravity anomaly, high magnetic anomaly and high resistivity anomaly in the northern part of the eastern part of Junggar basin may be mainly caused by the influx of larger density, stronger magnetic property and larger resistivity mantle substances into the middle crust along the fault in the northern margin of the Junggar basin.
Abstract: In order to study the features of geophysical field and deep structure of the eastern part of Junggar basin, we collected gravity and magnetic data with a scale of 1:1,000,000. Then, we calculated the isostatic gravity anomaly based on the Bouguer gravity anomaly data and the aeromagnetic anomaly by reduction to the pole (RTP) based on the aeromagn...
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