Yandong porphyry Cu deposit,Xinjiang, China—Geology,geochemistry and SIMS U–Pb zircon geochronology of host porphyries and associated alteration and mineralization     

《Journal of Asian Earth Sciences》2014

The Yandong porphyry copper deposit, located in the Eastern Tianshan Mountains, Xinjiang, China, is part of the Central Asian Orogenic Belt. The Yandong deposit is hosted by a volcanic complex in the Early Carboniferous Qi’eshan Group and a felsic intrusion. The complex consists of andesite, basalt, diorite porphyry, and porphyritic quartz diorite. The felsic intrusion is a plagiogranite porphyry emplaced within the complex. The diorite porphyry and plagiogranite porphyry yield SIMS zircon U–Pb ages of 340.0 ± 3 and 332.2 ± 2.3 Ma, respectively. Element geochemistry shows that both the complex and plagiogranite porphyry formed in the Dananhu–Tousuquan island arc, a Carboniferous magmatic arc.The diorite porphyry and plagiogranite porphyry are host porphyries, but the plagiogranite porphyry is a productive porphyry. It caused the porphyry-style Cu mineralization and associated alteration. The alteration assemblages include early potassic and propylitic assemblages. These were overprinted by a chlorite–sericite assemblage, which in turn was overprinted by a late phyllic assemblage. The phyllic alteration is associated with the highest Cu grades. The mineralization is recognized to include three stages, from early to late: stage 1, a potassic alteration associated with a chalcopyrite + pyrite assemblage; stage 2, represented by chlorite–sericite alteration with a chalcopyrite + pyrite assemblage; and stage 3, the main-ore stage that is marked by phyllic alteration with chalcopyrite + pyrite ± molybdenite and producing more than 70% of the total copper production at Yandong. Yandong may represent a common scenario for Paleozoic porphyry Cu systems in the Central Asian Orogenic Belt.  相似文献   

Geochemistry and petrogenesis of late Ediacaran (605–580 Ma) post-collisional alkaline rocks from the Katherina ring complex,south Sinai,Egypt     

《Journal of Asian Earth Sciences》2014

The Katherina ring complex (KRC) in the central part of south Sinai, Egypt, is a typical ring complex of late Neoproterozoic age (605–580 Ma). It was developed during the final tectono-magmatic stage of the north Arabian–Nubian Shield (ANS) during evolution of the Pan-African crust. The KRC includes Katherina volcanics, subvolcanic bodies, ring dykes and Katherina granitic pluton. The Katherina volcanics represent the earliest stage of the KRC, which was subsequently followed by emplacement of the subvolcanic bodies and ring dykes. The Katherina granitic pluton depicts as the latest evolution stage of the KRC that intruded all the early formed rock units in the concerned area. The Katherina volcanics are essentially composed of rhyolites, ignimbrite, volcanic breccia and tuffs. Mineralogically, the peralkaline rhyolites contain sodic amphiboles and aegirine. The rhyolite whole rock chemistry has acmite-normative character. The subvolcanic bodies of the KRC are represented by peralkaline microgranite and porphyritic quartz syenite. The ring dykes are semicircular in shape and consist mainly of quartz syenite, quartz trachyte and trachybasalt rock types. The Katherina subvolcanic rocks, volcanic rocks as well as the ring dykes are alkaline or/and peralkaline in nature. The alkaline granitic pluton forms the inner core of the KRC, including the high mountainous areas of G. Abbas Pasha, G. Bab, G. Katherina and G. Musa. These mountains are made up of alkaline syenogranite and alkali feldspar granite. The mantle signature recorded in the KRC indicates a juvenile ANS crust partial melting process for the generation of this system. The evolution of the KRC rocks is mainly dominated by crystal fractionation and crustal contamination. Mineral geothermometry points to the high temperature character of the KRC, up to 700–1100 °C.  相似文献   

基于高分数据的广东省矿山复绿现状遥感调查     

王耿明  吴海陆  罗雪丰 《江苏地质》2014,38(2):289-292

提出了矿山复绿的技术方法和技术路线。通过开展广东省矿山复绿遥感调查,获取较为真实的广东省矿山复绿最新状况。指出广东省矿山复绿存在的主要问题,并提出有益的建议和对策,希望遥感能够作为技术支撑更好地为矿政管理服务。  相似文献   

内蒙古阿木伊勒特铅锌矿床物化探异常特征及其地质意义     

魏小刚  徐德伟  刘振国 《华南地质与矿产》2014,(4):368-374

内蒙古阿木伊勒特铅锌矿床是2005年内蒙古自治区地质调查院承担的1︰50 000矿产地质调查时发现的,属于朝不楞—梨子沟多金属成矿带的西延部分。该区化探异常元素组合主要为Ag、Cu、Cd、Mo、Zn、Pb、As、Sd及铁族元素,经1︰5万与1︰1万土壤测量成果对比,异常重现性好、强度增高,浓集中心明显,与地表矿化蚀变带吻合较好。但常规物探激电面积测量未发现极化体的存在,为探测深部隐伏矿体,结合地质特征,布置CR法剖面,取得了较好的效果。总结该矿床的地质特征、物化探特征,提出其成矿规律,为本地区下一步找矿工作的开展提供借鉴。  相似文献   

Petrology and geochemistry of the ultramafic–mafic Mawpyut complex,Meghalaya: a Sylhet trap differentiation centre in northeastern India     

Srinanda Chaudhuri  Jyotisankar Ray  Christian Koeberl  Martin Thni  Riya Dutta  Abhishek Saha  Mousumi Banerjee 《Geological Journal》2014,49(2):111-128

The present article describes, for the first time, petrological and geochemical details of the Mawpyut differentiated complex which is related to the Sylhet trap located at Jaintia Hills district, Meghalaya, northeastern India. The Mawpyut complex occurs as an arcuate body that intrudes into the surrounding Shillong Group rocks. The complex in general contains ‘ultramafic’ and ‘mafic’ rocks, as well as minor syenitic veins that postdate the main units. The lithotypes correspond to cumulate and noncumulate units. The cumulate unit is represented by olivine clinopyroxenite, clinopyroxenite, plagioclase‐bearing ultramafic, olivine gabbronorite, mela‐gabbronorite, melagabbro, orthopyroxene gabbro, and gabbro, all with a pronounced cumulus texture. The noncumulate unit is marked by gabbro, monzonite, monzodiorite, and quartzsyenite. The use of several major and trace element variation diagrams suggests that magmatic differentiation led to the formation of cumulate and noncumulate units. In chondrite‐normalized REE diagrams the cumulate rocks show flat LREE and MREE patterns and a moderate positive Eu anomaly (in plagioclase‐bearing ultramafics) due to plagioclase cumulation. The rocks of the noncumulate unit show a strongly fractionated REE pattern and no Eu anomaly. The noncumulate mafic rocks are geochemically comparable to high‐phosphorous/high‐titanium basalts (HPT) indicative of low pressure fractional crystallization. In a primitive mantle‐normalized multielement diagram some of the cumulate rocks show pronounced negative anomalies for K and P, indicating anorogenic mafic magmatism in a within‐plate setting. The rocks of the noncumulate unit show a slight negative anomaly for Yb and a Nb–Ta trough, indicating a subduction‐related signature that perhaps is inherited from subducted sedimentary rocks incorporated during crustal contamination of the derived magma (left after crystal cumulation) with country rocks. Various trace element ratios for the cumulate mafic rocks indicate parent EMI/EMII/HIMU sources with a very limited crustal signature. The noncumulate mafic rocks (corresponding to the derived evolved magma) indicate EMI/EMII/HIMU sources with a pronounced crustal contamination. The Sr–Nd isotopic compositions of the Mawpyut samples typically plot in the continental flood basalt field, with an affinity to the EMII source. The isotopic compositions of the noncumulate rocks also clearly indicate crustal contamination. We suggest that partial melting (involving garnet in the residue) of the enriched mantle source EMI/EMII/HIMU could have derived the parental melt; this melt, in turn, underwent assimilation and fractional crystallization to produce the variety of cumulate‐noncumulate lithologies of the Mawpyut complex. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献