大别山燕山期中酸性小岩体钼成矿模型     

唐中刚 《四川地质学报》2012,32(3):299-303

大别山北麓钼(钨)矿带上的钼矿化,成因多与集中分布的中生代中酸性小岩体(花岗质斑岩)有关.信阳～汤家坪一带已知燕山期中酸性小花岗(斑)岩体40余处,且多具钼矿化,历经数年地质工作,已探明中型以上的钼矿床7处.该区内斑岩型钼矿床地质特征不尽相同,但成矿时代、围岩蚀变、岩体与矿化空间上的联系,都有一般斑岩钼矿床的共同特点.总结该区成矿酸性小岩体地质特征,成矿作用、成因、地球化学特征及成矿规律的研究成果,可为该区找矿提供借鉴作用.  相似文献   

青海南部曲麻莱县达考岩体地球化学特征及其构造环境     

白云山  段其发  牛志军  涂兵  李莉 《华南地质与矿产》2012,28(1):12-19

达考序列岩体由查肖叉得英云闪长岩、杂乃玛下黑云母二长花岗岩、抗涌正长花岗岩组成。单颗粒锆石U-Pb同位素年龄值为169±4 Ma,形成于中侏罗世,岩石化学成分表现为岩浆向富硅、富碱、富铝方向演化。稀土元素特征表现为轻稀土元素富集,重稀土元素平坦型。微量元素特征表现为富集大离子亲石元素Rb、K、Ba、Th,而Sr、Nb、Ta略显亏损,εNd（t）变化在-7.6~-8.1之间,（87Sr/86Sr）i值较高,变化于0.70969~0.71104之间。地球化学特征表明达考序列岩体形成构造背景为火山弧花岗岩,为壳幔混合产物。  相似文献   

西秦岭造山带礼县地区中川岩体LA-ICP-MS锆石U-Pb定年及其构造环境   总被引：3，自引：0，他引：3  

李婷  徐学义  陈隽璐  王洪亮  李智佩  张欣 《地质通报》2012,31(6):875-883

中川复式岩体位于西秦岭中带,与成矿关系密切,主体岩性为黑云母二长花岗岩,一般认为其形成于印支期。对中川岩体采集样品并进行了LA-ICP-MS锆石U-Pb定年和岩石化学分析。结果表明,岩体钾钠含量较高,Na2O/K2O<1;里特曼指数δ值为1.70～2.17,主体属高钾钙碱性系列;轻稀土元素富集,具中等程度的负Eu异常;K、Th、Rb等大离子亲石元素富集,同时显示出低Sr、低Yb的地球化学特征,形成于地壳加厚的构造环境。锆石U-Pb定年指示了08-49号样品黑云母二长花岗岩的形成时代最早为264.4Ma±1.3Ma,即二叠纪末期,略早于前人研究的结果。结合其构造环境,认为西秦岭从二叠纪末就开始了陆陆俯冲和地壳加厚的造山活动,并一直持续到三叠纪。  相似文献   

http://www.sciencedirect.com/science/article/pii/S1674987112000096     

Dedong Li  Yuwang Wang  Jingbin Wang  Zhaohua Luo  Jiulong Zhou  Zongfeng Yang  Cui Liu 《地学前缘(英文版)》2012,3(5):717-728

According to the metallogenic theory by transmagmatic fluid(TMF).one magmalic intrusion is a channel of ore-bearing fluids,but not their source.Therefore,it is possible to use TMF’s ability for injection into and for escaping from the magmatic intrusion to evaluate its ore-forming potential.As the ore-bearing fluids cannot effectively inject into the magmatic intrusion when the magma fully crystallized, the cooling time and rates viscosity varied can be used to estimate the minimum critical thickness of the intrusion.One dimensional heat transfer model is used to determine the cooling time for three representative dikes of different composition(granite porphyry,quartz diorite and diabase) in the Shihu gold deposit.It also estimated the rates viscosity varied in these lime interval.We took the thickness of dike at the intersection of the cooling time—thickness curve and the rates viscosity varied versus thickness curve as the minimum critical thickness.For the ore-bearing fluids effectively injecting into the magma,the minimum critical thicknesses for the three representative dikes are 33.45 m for granite porphyry,8.22 m for quartz diorite and 1.02 m for diabase,indicating that ore-bearing dikes must be thicker than each value.These results are consistent with the occurrence of ore bodies,and thus they could be applied in practice.Based on the statistical relationship between the length and the width of dikes.these critical thicknesses are used to compute critical areas:0.0003—0.0016 km~2 for diabase. 0.014—0.068 km~2 for quartz diorite and 0.011—0.034 km~2 for granite porphyry.This implies that orebearing minor intrusions have varied areas corresponding to their composition.The numerical simulation has provided the theoretical threshold of exposed thickness and area of the ore-bearing intrusion.These values can be used to determine the ore-forming potentials of dikes.  相似文献   

西秦岭岗岔—克莫金矿区石英闪长玢岩多金属“珠滴构造”及其找矿意义     

申俊峰  王书豪  徐立为  罗照华  李金春  刘海明  聂潇  秦玉良  彭自栋  牛刚  杜佰松  刘家军 《地学前缘》2019,26(5):222-242

西秦岭造山带北缘之金属成矿带是我国重要的斑岩型Cu-Au远景区,该带的德乌鲁岩体及其接触带是重要找矿潜力区。最新的野外调查发现,德乌鲁岩体东南缘接触带的石英闪长玢岩中发育大量含有多种金属矿物的椭圆形或近球形“珠滴构造”,且其矿物组合非常类似于临近的岗岔—克莫金矿床矿石矿物组合,即“珠滴”内含有大量金属矿物黄铁矿、毒砂、黄铜矿、方铅矿、闪锌矿、磁黄铁矿、钛铁矿和辉砷钴矿等,此外还发育有绿泥石、绿帘石、方解石、钾长石、钠长石、石英、绢云母、电气石、葡萄石、磷灰石、榍石和金红石等复杂的非金属矿物组合。详细的矿物学和地球化学研究结果表明,“珠滴”与寄主岩石属同源产物。绿泥石温度计和二长石温度计显示“珠滴”形成温度范围在297～435 ℃,角闪石全铝压力计显示寄主岩石形成压力为1.02～2.28 kbar。因此推断,“珠滴”形成于深部富含金属的流体,金属物质依附气泡按照“浮选”机制随岩浆侵位上升。当载有金属物质的气泡随着岩浆侵位到浅部时便快速解耦,其流体相逃逸,“珠滴”则被冷凝固结在岩浆圈闭之中。依据上述分析结果,认为携带金属物质的气泡把成矿元素运移至石英闪长玢岩体内,其中一些气泡把金属物质卸载到浅部,而大量的金属物质可能仍然留在深部石英闪长玢岩内。“珠滴构造”可能是深部成矿的重要指示标志。  相似文献   

Pore Structure Heterogeneity of the Xiamaling Formation Shale Gas Reservoir in the Yanshan Area of China: Evaluation of Geological Controlling Factors     

LI Xueyuan  CHEN Shangbin  WANG Xiaoqi  ZHU Yanming  CHANG Minghu  Clementine UWAMAHORO 《《地质学报》英文版》2019,93(3):588-603

Micro-heterogeneity is an integral parameter of the pore structure of shale gas reservoir and it forms an essential basis for setting and adjusting development parameters. In this study, scanning electron microscopy, high-pressure mercury intrusion and low-temperature nitrogen adsorption experiments were used to qualitatively and quantitatively characterize the pore structure of black shale from the third member of the Xiamaling Formation in the Yanshan area. The pore heterogeneity was studied using fractal theory, and the controlling factors of pore development and heterogeneity were evaluated in combination with geochemical parameters, mineral composition, and geological evolution history. The results show that the pore structure of the reservoir was intricate and complicated. Moreover, various types of micro-nano scale pores such as dissolution pores, intergranular pores, interlayer pores, and micro-cracks are well developed in member 3 of the Xiamaling Formation. The average porosity was found to be 6.30%, and the mean value of the average pore size was 4.78 nm. Micropores and transition pores provided most of the storage space. Pore development was significantly affected by the region and was mainly related to the total organic carbon content, vitrinite reflectance and mineral composition. The fractal dimension, which characterizes the heterogeneity, is 2.66 on average, indicating that the pore structure is highly heterogeneous. Fractal dimension is positively correlated with maturity and clay mineral content, while it is negatively correlated with brittle mineral content and average pore size. These results indicate that pore heterogeneity is closely related to thermal history and material composition. Combined with the geological background of this area, it was found that the pore heterogeneity was mainly controlled by the Jurassic magmatism. The more intense the magma intrusion, the stronger the pore heterogeneity. The pore structure and its heterogeneity characteristics present today are a general reflection of the superimposed geological processes of sedimentary-diagenetic-late transformation. The influence of magmatic intrusion on the reservoir is the main geological factor that should be considered for detailed evaluation of the Xiamaling Formation shale gas reservoir in the Yanshan area.  相似文献   

Shale-gas accumulation and pore structure characteristics in the lower Cambrian Niutitang shales,Cen-gong Block,South China     

W. Yang  G. Zhai  T. Dong  D. Gong  X. Yuan 《Australian Journal of Earth Sciences》2019,66(2):289-303

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内蒙古中部地区镁铁质-超镁铁质岩形成时代及地质意义     

党智财  李俊建  付超  唐文龙  刘跃  张鹏鹏  田杰鹏 《大地构造与成矿学》2019,(2):303-321

为探讨内蒙古中部地区镁铁质-超镁铁质岩形成时代及地球化学特征,完善区域成岩成矿年代学格架,本文对克布、黄花滩和小南山岩体进行了锆石U-Pb年代学及全岩地球化学分析。LA-ICP-MS锆石U-Pb测年获得克布和黄花滩镁铁质-超镁铁质岩结晶年龄分别为258±2 Ma(MSWD=2.3)和262±1 Ma(MSWD=0.51),属于中-晚二叠世,小南山辉长岩应形成于中-晚二叠世(～273 Ma)。全岩地球化学分析表明,三个岩体样品m/f值介于0.96～3.54之间,主要为镁铁质-超镁铁质岩,其稀土和微量元素曲线基本表现为轻稀土元素(LREE)和大离子亲石元素(LILE)相对富集,高场强元素(HFSE)相对亏损的相似性特征,但也有明显的区别,显示各岩体岩浆演化或分异程度可能不尽相同。综合区域研究资料表明,内蒙古中部地区晚古生代镁铁质-超镁铁质岩浆活动可能至少始于早二叠世(294Ma),持续至中-晚二叠世(273～258Ma),且二叠纪时期中亚造山带南缘较大范围内均发育较为活跃的幔源岩浆活动。克布、黄花滩和小南山岩体应形成于后碰撞伸展环境,其岩浆源区可能混染了俯冲流体交代改造的地幔楔物质,使3个岩体的岩石样品均显示具有富含大离子亲石元素和轻稀土元素,贫高场强元素等部分岛弧岩浆特征的信号。  相似文献   

Experimental soft‐sediment deformation caused by fluidization and intrusive ice melt in sand     

Pascal Bertran  Marianne Font  Arnaud Giret  Kevin Manchuel  Deborah Sicilia 《Sedimentology》2019,66(3):1102-1117

Identifying the driving mechanisms of soft‐sediment deformation in the geological record is the subject of debate. Thawing of ice‐rich clayey silt above permafrost was proved experimentally to be among the processes capable of triggering deformation. However, previous work has failed so far to reproduce similar structures in sand. This study investigates fluidization and intrusive ice formation from soil models in the laboratory. Experimental conditions reproduce the growth of ice‐cored mounds caused by pore water pressure increase during freeze‐back of sand in a permafrost context. Excess pore water pressure causes hydraulic fracturing and the development of water lenses beneath the freezing front. Later freezing of the water lenses generates intrusive ice. The main structures consist of sand dykes and sills formed when the increase in pore water pressure exceeds a critical threshold, and soft‐sediment deformations induced by subsidence during ice melt. The combination of processes has resulted in diapir‐like structures. The experimental structures are similar to those described in Pleistocene sites from France. These processes constitute a credible alternative to the seismic hypothesis evoked to explain soft‐sediment deformation structures in other European regions subjected to Pleistocene cold climates.  相似文献   

A self-consistent top–down model for differentiation in bimodal suites: application to the Sonju Lake Intrusion–Finland granite system (MN)     

C. C. Lundstrom 《International Geology Review》2017,59(11):1451-1470

The Sonju Lake Intrusion (SLI) is a 1200-meter thick layered mafic intrusion that directly underlies an equally large silicic pluton, the Finland granophyre (FG) within the Beaver Bay Complex of the Mid-Continent Rift (MN, USA). The SLI, with a simple mineralogical and compositional stratigraphy, provides an excellent case study for examining the changes in iron isotope ratios (δ⁵⁶Fe). Here new Fe isotope data along with ⁸⁷Sr/⁸⁶Sr for a set of stratigraphically controlled samples from the SLI and FG are presented. The Fe isotope data show systematic changes within two differentiation sequences found in the lowermost FG as well as the upper portion of the SLI. Specifically, δ⁵⁶Fe is observed to start at low values and increase to heavy values going stratigraphically up through each differentiation sequence. Within the middle portion of the SLI, δ⁵⁶Fe varies between 0 and 0.1. Two samples from the SLI bottom are isotopically lighter than the middle SLI. The origin of the Fe isotope variations is discussed in terms of recently proposed explanations. A quantitative model shows that the observed spatial variation is consistent with the prediction of a temperature gradient model. Using present constraints on equilibrium phase partitioning, the iron isotope variations do not appear consistent with production by fractional crystallization. Based on these observations, a top–down sill emplacement process coupled with in situ differentiation remains a viable alternative model for forming this layered intrusion.  相似文献