Tectonic Controls on the Formation of the Liwu Cu-rich Sulfide Deposit in the Jianglang Dome, S W China   总被引：2，自引：0，他引：2  

Dan-Ping Yan    Mei-Fu Zhou  Hong-Lin Song    Zhao-Ren Fu  Min Sun 《Resource Geology》2003,53(2):89-100

Abstract. The Liwu Cu‐rich sulfide deposit occurs within the Jianglang dome in the eastern margin of the Tibetan plateau. The dome consists of a core, a middle slab and a cover sequence. The main deposit is hosted in the core with minor ore bodies in the middle slab. The protolith of the core consists of clastic sedimentary rocks with inter‐layered volcanic rocks. All of the ore bodies are substantially controlled by an extensional detachment fault system. The ore bodies within the core are distributed along the S₂ foliation in the hinge of recumbent fold (D₂), whereas ore bodies with en echelon arrangement are controlled by the mylonitic foliation of the lower detachment fault. Ore bodies within the middle slab are oriented with their axes parallel to the mylonitic foliation. Pyrite and pyrrhotite from the ores contain Co ranging from 37 to 1985 ppm, Ni from 2.5 to 28.1 ppm, and Co/Ni ratios from 5 to 71. These sulfides have δ³⁴S values ranging from 1.5 to 7.5 % whereas quartz separates have δ¹⁸O values of 11.9 and 14.3 % and inclusion fluid in quartz has δD value of‐88.1 %. These features suggest that the deposit was of hydrothermal origin. Two ore‐forming stages are recognized in the evolution of the Jianglang dome. (1) A low‐temperature ore‐forming process, during the tectonic transport of the upper plate above the lower detachment, and the initial phase of the footwall updom‐ing at 192–177 Ma. (2) A medium‐temperature ore‐forming stage, related to the final structural development of the initial detachment at 131–81Ma. Within the core, the ore bodies of the first stage were uplifted to, or near, the brittle/ductile horizon where the ore‐forming metals were re‐concentrated and enriched. A denudation stage in which a compressional tectonic event produced eastward thrusting overprinted the previous structures, and finally denuded the deposit. The Liwu Cu‐rich sulfide deposit was formed during a regional extensional tectonic event and is defined as a tectono‐strata‐bound hydrothermal ore deposit.  相似文献   

赞皇变质窍隆黑云母^40Ar／^39Ar年代学研究及其对构造热事件的约束   总被引：6，自引：1，他引：6  

王岳军  范蔚茗  郭锋  彭头平  李超文 《岩石学报》2003,19(1):131-140

太行山南段赞皇变质杂岩中黑云母给出了1827～1793Ma的~(40)Ar/~(39)Ar坪年龄,代表了变质基底在经历高温热扰动后冷却到300℃时的热事件年龄。结合华北克拉通变质岩的其他年代学资料,认为1800Ma士华北克拉通内经历了一次广泛而强烈的构造热伸展事件,致使克拉通基底岩石快速抬升到中上地壳,其冷却速率>6℃/Ma,隆升速率>200m/Ma。赞皇变质杂岩内苍岩寺、岗西-榆底-黑水河东和坡底-郝庄韧性剪切带内糜棱岩中黑云母分别给出了1689Ma、1633Ma和1645Ma的~(40)Ar/~(39)Ar坪年龄,代表了剪切带变形的主变形时代,这一年龄也为约束长城系的底界年龄提供了新的信息。结合已有的热年代学资料,推断华北克拉通内部赞皇变质地区中元古代的冷却速率约0.4℃/Ma,隆升速率为15m/Ma。由此也表明,自中元古代以来华北克拉通内部未受到后期构造热事件的强烈扰动,赞皇变质杂岩并非中生代变质核杂岩,而是早元古代变质穹隆。  相似文献   

Cikidang Hydrothermal Gold Deposit in Western Java, Indonesia     

Mega F. Rosana  Hiroharu Matsueda 《Resource Geology》2002,52(4):341-352

Abstract. The Cikidang gold deposit, discovered in 1991, is located within the Bayah dome, a Tertiary-Quaternary volcanic zone at west end of Java, which is well known as a gold district (e.g., Pongkor and Cikotok mines). Typical low-sulfidation quartz-adularia-sericite(-calcite) vein deposits represent the gold deposit in the district.
The Cikidang vein system comprises four sub-parallel quartz-adularia-sericite(-calcite) veins that are rich in manganese oxide and limonite with very poor amount of sulfides. These vary from 0.5 to 2.7 m thick and extend for up to 1,000 m long. The vein trends roughly N-S and dip 60 to 86° toward west. The ore grades vary from trace to 74.9 g/t Au and 1.2 to 225.0 g/t Ag. A K/Ar age determination on adularia yielded 2.4 Ma for the Cikidang vein.
The ore minerals are represented by electrum, argentite, aguilarite and pyrite. Electrum shows the compositional ranges of Ag (50–65 atom %). The gangue minerals are dominated by quartz with variable amounts of calcite, sericite, adularia, clay minerals, manganese oxide and limonite. The vein textures are so variable as banded, colloform, comb, brecciated and massive. Host rocks, composed of Miocene lapilli tuff and breccia, suffered from pervasive hydrothermal alterations. Wall rocks adjacent to the vein are characterized by argillic and propylitic alteration.
The fluid inclusion study of the Cikidang vein shows homogenization temperatures ranging from 170 to 260°C. Salinities are low, generally below 3 wt% NaCl equivalent. Oxygen isotope results suggest meteoric water in origin for ore fluids responsible for the Cikidang deposit.  相似文献   

Origine des variations latérales des dépôts yprésiens dans la zone des dômes en Tunisie septentrionaleOrigin of lateral variations of the Ypresian deposits in the dome zone in northern Tunisia     

Hmidou El Ouardi 《Comptes Rendus Geoscience》2002,334(2):141-146

In the Mejez El Bab–Testour area (northern Tunisia), the Early Eocene extension induced block tilting and salt tectonics of the Triassic evaporites. Tectonic events and halokinesis have determined the organization of Ypresian sediments. Diapiric structures have been generated during Cretaceous along the east–west, north–south and NE–SW major faults and emphasised during Lower Eocene. In this region, the Ypresian deposits constitute a filling sequence and show several thickness and facies variations. They correspond to a Nummulitic and Globigerina mixed facies characterizing a platform-basin transition zone. To cite this article: H. El Ouardi, C. R. Geoscience 334 (2002) 141–146.  相似文献   

羌塘盆地中部隆起的演化及其在油气勘探中的意义   总被引：9，自引：0，他引：9  

方立敏  鲁兵等 《地质论评》2002,48(3):279-283

本文从沉积演化的角度分析了羌塘盆地中西部“冈玛错－西雅尔岗”隆起的演化过程，隆起在晚二叠世处于雏型发育阶段，晚三叠世肖茶卡－中株罗世雀昏时期为定型阶段，白垩纪－新生代为变形改造阶段。每一阶段隆起都控制着不同形式的生储盖组合的发育。隆起周缘具半地堑结构的凹陷是良好的油气聚集带之一。近隆起带北侧的构造层变形强度不大，对油气的后期保存比较有利。  相似文献   

Potential field constraints on the deep structure of the Lugo gneiss dome (NW Spain)     

Puy Ayarza  Jos R. Martínez Cataln 《Tectonophysics》2007,439(1-4):67-87

The Lugo gneiss dome, in the NW Iberian Massif (Spain) is a Variscan structure developed during late stages of orogenic collapse. Crustal extension was mainly accomplished by two kilometre-scale conjugate extensional shear zones and by the late development of the dome and a huge normal fault. These structures overprint previous contractional recumbent folds and a thrust fault. The Lugo dome and its southward continuation, the Sanabria dome, are the site of the conspicuous Eastern Galicia Magnetic Anomaly (EGMA), a N–S band, 50 km wide and 190 km long, with a maximum amplitude of 190 nT. Integrated potential field modelling of the EGMA and its corresponding gravity signature have been carried out aided by constraints provided by the measurement of c. 900 magnetic susceptibilities and by previous geophysical data, mainly seismic refraction and reflection profiles. Results suggest that a large volume of low-density migmatites and associated inhomogeneous granites are the main source of the magnetic anomaly. Small massifs of basic and ultrabasic rocks inside the migmatites and high-susceptibility iron ore bodies sparsely distributed in low-grade Middle Ordovician slates are also thought to contribute to the anomaly but to a minor extent. Although otherwise similar to other gneiss domes, the Lugo dome is accompanied by a striking magnetic anomaly whose origin is discussed in terms of the tectonic evolution of this structure and the provenance of the magnetite-bearing migmatites and inhomogeneous granites that core it.  相似文献   

冀北双井子穹状火山与银铅(锌)矿化的关系     

夏国礼  潘洪儒  胡醒民 《华北地质》2005,28(2):94-99

通过区域地质调查，认为丰宁满族自治县双井子南西一带的晚侏罗世张家口期火山-侵入活动、同熔型岩浆作用、火山通道及火山断裂与银、铅(锌)矿化关系密切。在整体的火山-侵入活动过程中，先期的火山活动可使成矿物质初步富集，后期的岩浆侵入作用封闭性好，热量充足，可使成矿物质进一步叠加富集成矿。同熔型岩浆作用形成的石英正长斑岩是成矿物质的主要提供者，岩石中Ag、Pb、Zn等成矿元素的丰度值普遍较高，约为世界同类岩石平均值的4～10倍，呈强富集状态。火山通道深达上地幔，有利于岩浆向上运移及深部含矿热液的上升环流，是良好的导岩导矿构造。火山周边断裂规模相对较大，其内多形成构造角砾岩带，是成矿物质沉淀、富集的理想场所和最有利的容矿构造。放射状断裂是沟通火山通道和火山周边断裂并使含矿热液从火山通道向火山周边断裂运移的重要渠道，起到配矿构造的作用。  相似文献   

国产地球辐射表长波滤光罩性能的测试研究   总被引：1，自引：0，他引：1       下载免费PDF全文

王炳忠 《应用气象学报》2000,11(3):371-376

滤光罩是地球辐射表的关键部件, 其性能直接影响着该仪器的性能与质量.利用LOWTRAN 7和国产各种滤光罩实测的光谱透射比数据, 对不同的模式大气下各滤光罩有效透射比等性能指标进行计算, 并与Eppley罩的研究情况作了对比.结果表明, 国产罩的各项性能指标并不次于Eppley罩.  相似文献   

Broadband seismic experiment at Merapi Volcano, Java, Indonesia: very-long-period pulses embedded in multiphase earthquakes     

D. Hidayat  B. Voight  C. Langston  A. Ratdomopurbo  C. Ebeling 《Journal of Volcanology and Geothermal Research》2000,100(1-4)

Multiphase (MP) and low frequency (LF) earthquakes with spectral peak amplitudes at 3–4 and 1 Hz, respectively, are two common types of shallow volcanic earthquakes previously recognized at Merapi Volcano. Their mechanisms are poorly understood but MPs have been temporally associated with lava dome growth. We conducted a seismic experiment in January–February 1998, using four broadband seismographs to investigate the nature of seismic activity associated with dome growth. During our experiment, Merapi experienced mild dome growth with low-level seismic activity. We compare our data to that recorded on a local short-period (SP) network, with the following preliminary results.MP and LF events as recorded and classified on the short-period network instruments were recognized on the broadband network. Frequency spectrograms revealed similar patterns in the near summit region at widely separated broadband stations. Higher frequency spectra than previously recognized were identified for both MP and LF events, and were strongly attenuated as a function of radial distance from the source. Thus the spectral characteristics of these events as recorded on far-field stations are not fully indicative of the source processes. In particular, many events classified as LF-type appear to have much high frequency energy near the source. This aspect of these so-called LF earthquakes, and their association with very-long-period (VLP) pulses, suggests that many events identified in the far-field as LF events are in actuality a variety of the MP event and involve similar source processes. Broadband records indicated that simple large-amplitude VLP pulses were embedded in MP and LF wavetrains. From event to event these pulses were similar in their waveforms and had periods of 4 s. VLP events embedded in LF and MP earthquakes were located using particle motions. The epicenters were clustered in a central region of the dome complex, and preliminary source depths were within about 100 m of the dome surface, suggesting a source region deep within the dome or the uppermost conduit. A similar source location was established by study of MP high-frequency onsets. Our broadband data suggests that we have recorded both elastic seismic waves and a simple embedded pulse that is interpreted to represent a surface tilt at the seismometer site. The inferred tilt indicates an inflation and subsequent deflation, possibly caused by a gas pressure pulse or episodic shallow magma transport with stick-slip movement of the conduit wall.  相似文献   

中国大陆显生宙俯冲型、碰撞型和复合型片麻岩穹窿(群)   总被引：8，自引：2，他引：6  

许志琴  马绪宣 《岩石学报》2015,31(12):3509-3523

片麻岩穹窿(gneiss dome)是中下地壳热动力学过程产生的、与岩浆作用(或混合岩化作用)密切相关的穹窿状构造。片麻岩穹窿大部分是地壳深层次变动的产物,在世界范围内几乎出露在所有的折返造山带中,反映了所在地区地壳的大幅度抬升。片麻岩穹窿核部主要是无或弱岩浆组构的花岗岩体和高级变质岩(例如混合岩),边部是具有岩浆组构的花岗片麻岩,幔部由来自地壳深部的高级片岩和片麻岩组成。片麻岩穹窿的形成经历从垂直上升的地壳流导致的岩浆上涌的挤压收缩机制到岩浆体侵位的顶部伸展机制的转化过程。根据片麻岩穹窿的岩石组合、组构特征、成因机制和大地构造背景以及片麻岩穹窿与地壳流关系的分析,结合中国大陆典型片麻岩穹窿的研究,提出中国大陆显生宙的片麻岩穹窿和片麻岩穹窿群可以划分为与大洋岩石圈板片俯冲增生与随后的折返造山相关的"俯冲型"片麻岩穹窿(群),如秦岭片麻岩穹窿;与陆陆碰撞折返造山有关的"碰撞型"片麻岩穹窿(群),如北喜马拉雅拉轨岗日片麻岩穹窿(群)和松潘甘孜雅江片麻岩穹窿(群);与俯冲和碰撞的叠合作用有关的"复合式"片麻岩穹窿(群),如帕米尔空喀山片麻岩穹窿和东冈底斯林芝片麻岩穹窿(群)。  相似文献