滇西地区壳幔解耦与腾冲火山区岩浆活动的深部构造研究   总被引：4，自引：0，他引：4  

胥颐  钟大赉  刘建华 《地球物理学进展》2012,27(3):846-855

根据青藏东部边缘的深部地球物理资料,分析了滇西地区壳幔耦合和腾冲火山区岩浆活动的深部构造特征,确认了地幔各向异性与上地幔速度结构(包括P波速度和S波速度)的内在联系,指出产生这一结果的原因与以腾冲火山区为中心的地幔热物质上涌有关:上地幔顶部平均温度升高导致介质强度降低,在印支块体的侧向挤压或印缅块体的向东俯冲作用下发生韧性变形,造成滇西地区地幔各向异性的快波方向与青藏东部地壳块体的旋转方向不一致.此外,鉴于中下地壳低速层的横向非均匀性,估计韧性流动并非贯通青藏高原的东部边缘,而是被不同的构造块体和边界断裂限定在局部地区.总体而言,滇西地区下地壳的地震波速度和电阻率偏低,具备发生韧性变形的构造条件.作为地壳和上地幔之间的解耦层,它使得青藏东部地壳块体旋转产生的构造应力未能传输至上地幔.腾冲火山区的地壳结构与不同时期的岩浆活动有关,火山区东侧的高速结构代表了上新世时期火山通道内冷凝固结的岩浆侵入体或难以挥发的高密度残留物质,火山区西侧的低速结构反映了更新世以来持续至今的岩浆活动,壳内岩浆源主要分布在10～20km的深度范围内,横向尺度约为15～20km,有可能通过地壳深部的断裂与上地幔岩浆源区相连,估计腾冲火山区下方的岩浆活动将持续进行.  相似文献   

Tectonics,magmatism, and mineralization of Circum–Balkash–Junggar area in the Central Asian Orogenic Belt     

Wenjiao Xiao  Ping Shen  Xuanhua Chen 《International Geology Review》2017,59(9):1047-1052

ABSTRACT

The Circum–Balkhash–Junggar area, including mostly Kazakhstan, NW China, Russia, Kyrgyzstan, Tajikistan, Uzbekistan, and Mongolia, occupies an important tectonic position of the Central Asian Orogenic Belt (CAOB) (Figure 1). Tectonically, this vast area records the complicated geodynamic processes, among which the most prominent stages are the formation of the U-shaped Kazakhstan Orocline and its interactions with adjacent Altai (Altay), Junggar (West Junggar, Junggar Basin, and East Junggar), and Tianshan orogenic collages in the Palaeozoic, bearing large-scale mineral deposits. The formation of the Late Palaeozoic mineral deposits is related to the tectonic evolution of the Devonian and Carboniferous–Permian volcano-magmatic arcs in the region. However, the link between the metallogeny and the evolution of the volcano-magmatic arcs is not well understood and existing geodynamic models have not explained satisfactorily the mechanism of the huge metallogenic belt. Therefore, this special issue focuses on the formation of the Late Palaeozoic porphyry Cu deposits and their link to the tectonic evolution of the Devonian and Carboniferous–Permian volcano-magmatic arcs with emphasis on comparative studies across the international borders.  相似文献   

江西金鸡窝铜矿床花岗闪长斑岩黑云母矿物学特征及其对岩石成因与成矿的指示     

杜后发  赖天功  江媛媛  范鹏飞  龚维强 《岩石矿物学杂志》2017,36(3):329-342

通过对金鸡窝铜矿区花岗闪长斑岩进行详细的岩相学研究和黑云母成分的电子探针原位分析,厘定了黑云母形成的物理化学条件,并探讨了其成岩成矿意义。电子探针研究显示:花岗闪长斑岩中黑云母的Ti为0.44~0.47apfu,Mg/(Mg+Fe)比值范围为0.58~0.62,结合其化学成分在10 TiO_2-Fe O*-Mg O图解和Mg-(Fe2++Mn)-(AlⅥ+Fe3++Ti)图解中的投影,认为该岩体中黑云母具有富镁贫铁特征,属于原生黑云母。黑云母氧化系数(fO)范围为0.31~0.67,MF值范围为0.38~0.41,Mg O含量为13.27%~14.28%,K2O为3.59%~8.93%,Na2O为0.26%~3.28%,Fe O为15.74%~17.30%,TiO_2为3.93%~4.19%,Al2O3为13.52%~14.19%,单位分子中阳离子数AlⅣ为2.00~2.24 apfu,AlⅥ为0.15~0.41 apfu,指示其岩体属于高钾质钙碱性系列的同熔型(或I型)花岗岩,具有壳幔混源成因的特征。黑云母结晶温度为734~748℃,结晶压力为71~89 MPa,相当于深度2.7~3.3 km,平均深度为3.0 km。黑云母化学成分投点主要落在Fe2O3-Fe3O4缓冲线之上,表明其形成于高氧逸度环境,且有利于铜矿的形成。  相似文献   

山东乳山英格庄金矿床地质特征及成因浅析     

邱介玲  ;王厚琴  ;丁正江  ;周会青  ;姜瑞源  ;耿仙湖 《山东地质》2009,(12):26-30

英格庄金矿为胶东牟平-乳山成矿带上的一个中型金矿床。该矿床矿体严格受金牛山断裂带控制,呈脉状、透镜状和囊状平行斜列式产出;矿体平均厚1．58～1．98m,平均品位3．96×10^-6～4．77×10^-6。矿石类型主要为黄铁矿石英脉型;矿石中金属矿物主要为银金矿、自然金、黄铁矿等。围岩蚀变包括绢云母化、硅化、绿泥石化、黄铁矿化等。研究表明,英格庄金矿床为一中低温热液脉型金矿,属Groves等提出的造山型金矿范畴。  相似文献   

利用海底电缆探测太平洋地区地幔结构的研究进展     

梁朋飞  师学明 《地球物理学进展》2013,28(3)

介绍了地幔电性结构、地幔温度、地幔含水量等参数对地球动力学和地幔动力学过程的重要科学意义,综述了近年来利用海底电缆在该领域的主要研究进展.本文首先介绍了日本利用海底电缆探测地幔深部结构的方法原理与发展历程,然后阐述了该方法的观测方式、观测系统与仪器,综述了国际上近年来利用海底电缆在环太平洋地区海底的观测资料进行地幔一维电导率结构、三维电导率分布的研究进展.基于海底电缆的观测数据进行反演的结果表明,太平洋海域地区地球深部存在410 km,660 km的电导率不连续面,此不连续面与地震资料的波速不连续面基本一致,为地幔不连续面提供了新的地球物理证据.在根据由海底电缆观测数据反演得到的太平洋地区地球内部电导率分布基础上,综述了综合深部地震波速、岩石高温高压实验等,将电导率的分布转换为地球内部的温度场分布、推导地幔过渡带水的浓度进而转换为地幔过渡带的含水百分比(含水量)的方法技术与研究进展.研究结果表明,夏威夷和北日本海地幔过渡带电导率异常主要受温度控制,菲律宾海域地幔过渡带的电导率异常除了和温度有关外,还受含水量影响,该处地幔过渡带的含水量大约在1％左右.这些研究表明,海底电缆探测方法,在地球深部探测尤其是地幔不连续面的探测、地幔温度场分布与特征、地幔含水量等方面有重要的作用.最后,展望了海底电缆探测方法的研究与发展,这些研究方法及成果对认识中国海域地球内部机构提供一定的参考.  相似文献   

川滇黔相邻区铅锌矿床分布特征及成矿规律   总被引：1，自引：0，他引：1  

陈大  吴林峰 《四川地质学报》2012,32(3):304-308

从分析川滇黔相邻区铅锌矿床分布特征着手,以成矿元素继承演化为主线,阐述了该区从最初铅锌地球化学块体形成,到古生代受岩相古地理控制的元素演化、成矿期元素活化、流体成矿,最后造山期叠加改造成矿的规律.  相似文献   

湘黔汞矿带旋扭构造动力作用与成矿规律   总被引：1，自引：0，他引：1  

雷义均  戴平云  段其发  王国强  赵武强 《大地构造与成矿学》2012,36(4)

湘西黔东地区,在古生代沉积盖层中,北北东向保靖-铜仁断裂带的东侧,发育一系列北东向平移逆冲压扭性断裂构造带,它们均具有相似的变形特征和动力学机制,构成一个大型压扭性旋扭构造系统。旋扭构造控制了湘黔汞矿带的分布,其中北东向断裂带控制了汞矿带内各矿田的展布,而由北东向断裂带所派生的次级张扭性断裂裂隙带,则控制了单个矿体或矿床的产出和定位,特大型和大型汞矿床均产于旋扭构造的应力强区内。  相似文献   

Petrogenesis and geodynamic significance of the late Palaeozoic Dongwanzi Complex,North China Craton: constraints from petrological,geochemical, and Os-Nd-Sr isotopic data     

《International Geology Review》2012,54(12):1521-1540

The late Carboniferous Dongwanzi Complex in the northern North China Craton is composed of intrusive pyroxenite, hornblendite, gabbro, and syenite. The mafic-ultramafic rocks of the complex exhibit typical cumulate textures, curved-upward REE patterns, and variable contents of compatible elements, suggesting a cumulate origin. The syenite shows Sr-Nd isotopic ratios similar to the mafic-ultramafic complex and positive Eu anomalies in the chondrite-normalized REE patterns, suggesting that the syenite may represent residual melt after significant fractional crystallization of mafic melt. The mafic-ultramafic cumulates have low HREE abundance and high (Tb/Yb)_N (2.5–4.2) and Dy/Yb ratios (>2), indicating that they may have originated from melting of garnet peridotite in the mantle. The Dongwanzi Complex is characterized by a large variation in Sr-Nd isotopic composition, with I_Sr = 0.7035 to 0.7052 and ε_Nd(t) = ?4.0 to +5.2, which may be accounted for by mixing melts of depleted asthenospheric and enriched lithospheric sources. The radiogenic Os isotopic compositions of the complex ((¹⁸⁷Os/¹⁸⁸Os)_i = 0.1344 to 0.3090) suggest slight contamination by mafic lower crust (≤2.5% based on Os isotopic modelling). The Dongwanzi Complex exhibits arc-related whole-rock and mineral geochemical affinities, such as enrichment in LILE (e.g. Sr, Ba, K) and depletion in HFSE (e.g. Nb, Ta, Ti). The abundance of hornblende and high CaO contents (22–24 wt.%) of clinopyroxene suggest that the source was rich in H₂O, probably due to the formation above a subduction zone. We conclude that the Dongwanzi Complex and the related crust–mantle interactions probably reflect formation in a back-arc extensional environment related to the subduction of the Palaeo-Asian Ocean beneath the northern margin of the North China Craton in late Palaeozoic time.  相似文献   

Sedimentary Crust and Metallogeny of Granitoid Affinity: Implications from the Geotectonic Histories of the Circum‐Japan Sea Region,Central Andes and Southeastern Australia     

Kohei Sato 《Resource Geology》2012,62(4):329-351

Metallogeny of granitoid affinity was reviewed from the aspect of geotectonic history of the continental crust, particularly of the genesis of sedimentary crust involved in magmatism. The redox state of granitoids and related mineralization shows a remarkable contrast between the east and west sides of the Pacific Rim, but if examined closely, the reduced‐type and oxidized‐type granitoid provinces are juxtaposed in three regions: the circum‐Japan Sea region, the central Andes, and the Lachlan Fold Belt in southeastern Australia. Comparative study of these regions revealed that the reduced‐type magmatism associated with Sn mineralization generated in thick sedimentary crust which formed in three geotectonic environments: (i) accretionary terrane along a subduction zone (e.g. Jurassic East Asia), (ii) continental rift (e.g. Early Paleozoic Andes), and (iii) mega‐fan (e.g. Early Paleozoic southeastern Australia). A collisional orogen can provide large amounts of clastic sediment to these environments. The age gap between the magmatism and sedimentation varies depending on the tectonic evolution of individual regions. Thin sedimentary crust may not play an essential role for the reduced‐type magmatism. The oxidized‐type magmatism associated with porphyry Cu and other mineralization generated in the crust which was initially carbon‐free igneous crust or modified from sedimentary crust by magmatism. Subduction‐related basaltic magmas are relatively oxidized, and may enhance fO₂ conditions of granitoid activity. Repeated magmatism in a monotonous convergent margin may be favorable for porphyry Cu mineralization as exemplified in the eastern Pacific Rim.  相似文献   

Geological, geochemical characteristics and isotope systematics of the Longqiao iron deposit in the Lu-Zong volcano-sedimentary basin, Middle-Lower Yangtze (Changjiang) River Valley, Eastern China   总被引：8，自引：0，他引：8  

Zhou Taofa  Wu Mingan  Fan Yu  Duan Chao  Yuan Feng  Zhang Lejun  Liu Jun  Qian Bing  Franco Pirajno  David R. Cooke 《Ore Geology Reviews》2011,43(1):154-169

The Middle-Lower Yangtze (Changjiang) River Valley metallogenic belt is located on the northern margin of the Yangtze Craton of eastern China. Most polymetallic deposits in the Changjiang metallogenic belt are clustered in seven districts where magmatism of Mesozoic age (Yanshanian tectono-thermal event) is particularly extensive. From west to east these districts are: E-dong, Jiu-Rui, Anqing-Guichi, Lu-Zong, Tong-Ling, Ning-Wu and Ning-Zhen. World-class iron ore deposits occur in the Lu-Zong and Ning-Wu ore clusters, which are mainly located in continental fault-bound volcanic-sedimentary basins. One of these deposits is the Longqiao iron deposit, discovered in the northern part of the Lu-Zong Basin in 1985. This deposit consists of a single stratabound and stratiform orebody, hosted in sedimentary carbonate rocks of the Triassic Dongma'anshan Formation. A syenite pluton (Longqiao intrusion) is situated below the deposit. The iron ore is massive and disseminated and the ore minerals are mainly magnetite and minor pyrite. Wall rock alteration mostly consists of skarn minerals, such as diopside, garnet, potassic feldspar, quartz, chlorite, phlogopite and anhydrite. Thin sedimentary siderite beds of Triassic age occur as relict laminated ore at the top and the margin of the magnetite orebody. These sideritic laminae are part of Triassic evaporite-bearing carbonate deposits (Dongma'anshan Formation).Sulfur isotopic compositions show that the sulfur in the deposit was derived from a mixture of magmatic hydrothermal fluids and carbonate–evaporite host rocks. Similarly, the C and O isotopic compositions of limestones from the Dongma'anshan Formation indicate that these rocks interacted with magmatic hydrothermal fluids. The O isotopic compositions of the syenitic rocks and minerals from the deposit show that the hydrothermal magnetite and skarn minerals were formed from magmatic fluids. The Pb isotopic compositions of sulfides are similar to those of the Longqiao syenite. Phlogopite coexisting with magnetite in the magnetite ores yielded a plateau age of 130.5 ± 1.1 Ma (2σ), whereas the LA-ICP MS age of the syenite intrusion is 131.1 ± 1.5 Ma, which is slightly older than the age of phlogopite.The Longqiao syenite intrusion may have crystallized from a parental alkaline magma, generated by partial melting of lithospheric mantle, during extensional tectonics. The ore fluids were probably first derived from magma at depth, later emplaced in the sedimentary rocks of the Dongma'anshan Formation, where it interacted with siderite and evaporite-bearing carbonate strata, resulting in the formation of magnetite and skarn minerals. The Longqiao iron deposit is a skarn-type stratabound and stratiform mineral system, genetically and temporally related to the Longqiao syenite intrusion. The Longqiao syenite is part of the widespread Mesozoic intracontinental magmatism (Yanshanian event) in eastern China, which has been linked to lithospheric delamination and asthenospheric upwelling.  相似文献