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961.
962.
上扬子地区晚震旦世灯影组及其相应地层白云岩中广泛发育一种外形奇特的具有圈层结构的肾球状体、椭球体、葡萄体及不规则状的球体(以下统称为葡萄体),宏观上呈钙华状成片产出,沿层面或裂隙分布,大量学者认为其为受大气淡水影响形成的。在详细野外观察描述的基础上,应用偏光显微镜、阴极发光和扫描电镜等分析测试手段,对四川南江杨坝地区灯影组一段白云岩中的葡萄体进行了研究,结果表明:葡萄体为具核心和明暗相间皮壳层的半球体,矿物组分以白云石为主,局部含少量自生石英,为围岩固结成岩后的产物;核心及暗色皮壳层中发育藻黏结集合体,并见大量不规则的微生物丝状体,且矿物组分中含有较高的碳元素,发较亮的红色阴极光,结合海底硬底的存在,说明其为海水环境中的生物-化学沉积物;葡萄体的外层主要为亮色皮壳层,呈等厚亮晶纤状胶结物,多发暗红色阴极光,并造成葡萄体间呈多面体交汇,说明后期葡萄体的形成以胶结作用为主,为海水潜流带的产物;葡萄体的大小和形态与基底上不规则凸起的形态及生长空间特征密切相关,固定的生长质点和规则的结构指示葡萄体形成于稳定的水体中;葡萄状白云岩的原始组构应为文石或高镁方解石,扫描电镜下呈晶粒结构,为白云石化作用的产物;葡萄集合体的组分、阴极发光性与其围岩相似,按照其产状和形态特征,把这种具有固定生长质点且具等厚皮壳层的半球体称作葡萄状构造,应为生物-化学成因的沉积-成岩构造,形成于稳定的海水中。 相似文献
963.
964.
965.
966.
东天山博格达造山带晚石炭世柳树沟组为一套由玄武岩和流纹岩组成的双峰式火山岩,形成于晚石炭世,其Si O_2含量介于46.18%~46.56%和76.06%~76.25%之间,具有明显的Daly成分间断。其中,玄武岩具富Na贫K特征,Ti O_2、Al_2O_3、Ca O和MgO含量均较高,∑REE为75.54×10~(-6)~80.22×10~(-6),LREE/HREE值为3.00~3.12,以富集Ba、Rb等大离子亲石元素(LILE)和不相容元素(P、K),相对亏损Ti、Ta、Nb等高场强元素(HFSE)和不相容元素(U、Th)为特征;流纹岩Na_2O/K_2O值为0.32~0.36,属低Ti、低Mg类流纹岩,∑REE为520.72×10~(-6)~595.26×10~(-6),LREE/HREE值为5.60~6.53,具有Rb、Th、K、La、Ce、Zr、Hf、Sm等元素的富集以及Ba、U、Ta、Nb、Sr、P和Ti元素的亏损特征。柳树沟组双峰式火山岩形成于大陆裂谷环境,具板内成因特征,玄武岩可能为亏损尖晶石相地幔橄榄岩向石榴石相地幔橄榄岩过渡相较高程度部分熔融的产物,受到地壳物质混染;流纹岩具典型的A型花岗岩的地球化学特征。 相似文献
967.
Andrew D. La Croix Jianhua He Valeria Bianchi Jiahao Wang Sebastian Gonzalez Jim R. Undershultz 《Sedimentology》2020,67(1):457-485
Interpretations of palaeodepositional environments are important for reconstructing Earth history. Only a few maps showing the Jurassic depositional environments in eastern Australia currently exist. Consequently, a detailed understanding of the setting of Australia in Gondwana is lacking. Core, wireline logs, two-dimensional and three-dimensional seismic from the Precipice Sandstone and Evergreen Formation in the Surat Basin have been used to construct maps showing the evolution of depositional environments through the Early Jurassic. The results indicate the succession consists of three third-order sequences (Sequence 1 to Sequence 3) that were controlled by eustatic sea level. The lowstand systems tract in Sequence 1 comprises braidplain deposits, confined to a fairway that parallels the basin centre. The strata were initially deposited in two sub-basins, with rivers flowing in different orientations in each sub-basin. The transgressive systems tract of Sequence 1 to lowstand systems tract of Sequence 3 is dominated by fluvio–deltaic systems infilling a single merged basin centre. Finally, the transgressive and highstand systems tracts of Sequence 3 show nearshore environments depositing sediment into a shallow marine basin. In the youngest part of this interval, ironstone shoals are the most conspicuous facies, the thickness and number of which increase towards the north and east. This study interprets a corridor to the open ocean through the Clarence–Moreton Basin, or the Carpentaria and Papuan basins, evidence of which has been eroded. These results challenge a commonly held view that eastern Australia was not influenced by eustasy, and propose a more dynamic palaeogeographic setting comprising a mixture of fluvial, deltaic and shallow marine sedimentary environments. This work can be used to unravel the stratigraphic relationships between Mesozoic eastern Australian basins, or in other basins globally as an analogue for understanding the complex interplay of paralic depositional systems in data poor areas. 相似文献
968.
NING Chuanxiang MA Zhongliang JIANG Zhenxue SU Siyuan LI Tingwei ZHENG Lunju WANG Guozhen LI Fengxun 《《地质学报》英文版》2020,94(2):352-363
To reveal the effect of shale reservoir characteristics on the movability of shale oil and its action mechanism in the lower third member of the Shahejie Formation(Es3l), samples with different features were selected and analyzed using N2 adsorption, high-pressure mercury injection capillary pressure(MICP), nuclear magnetic resonance(NMR), high-speed centrifugation, and displacement image techniques. The results show that shale pore structure characteristics control shale oil movability directly. Movable oil saturation has a positive relationship with pore volume for radius > 2 μm, as larger pores often have higher movable oil saturation, indicating that movable oil is present in relatively larger pores. The main reasons for this are as follows. The relatively smaller pores often have oil-wetting properties because of organic matter, which has an unfavorable effect on the flow of oil, while the relatively larger pores are often wetted by water, which is helpful to shale oil movability. The rich surface provided by the relatively smaller pores is beneficial to the adsorption of immovable oil. Meanwhile, the relatively larger pores create significant pore volume for movable oil. Moreover, the larger pores often have good pore connectivity. Pores and fractures are interconnected to form a complex fracture network, which provides a good permeability channel for shale oil flow. The smaller pores are mostly distributed separately;thus, they are not conducive to the flow of shale oil. The mineral composition and fabric macroscopically affect the movability of shale oil. Calcite plays an active role in shale oil movability by increasing the brittleness of shale and is more likely to form micro-cracks under the same stress background. Clay does not utilize shale oil flow because of its large specific surface area and its block effect. The bedding structure increases the large-scale storage space and improves the connectivity of pores at different scales, which is conducive to the movability of shale oil. 相似文献
969.
There are abundant coal and coalbed methane(CBM)resources in the Xishanyao Formation in the western region of the southern Junggar Basin,and the prospects for CBM exploration and development are promising.To promote the exploration and development of the CBM resources of the Xishanyao Formation in this area,we studied previous coalfield survey data and CBM geological exploration data.Then,we analyzed the relationships between the gas content and methane concentration vs.coal seam thickness,burial depth,coal reservoir physical characteristics,hydrogeological conditions,and roof and floor lithology.In addition,we briefly discuss the main factors influencing CBM accumulation.First,we found that the coal strata of the Xishanyao Formation in the study area are relatively simple in structure,and the coal seam has a large thickness and burial depth,as well as moderately good roof and floor conditions.The hydrogeological conditions and coal reservoir physical characteristics are also conducive to the enrichment and a high yield of CBM.We believe that the preservation of CBM resources in the study area is mainly controlled by the structure,burial depth,and hydrogeological conditions.Furthermore,on the basis of the above results,the coal seam of the Xishanyao Formation in the synclinal shaft and buried at depths of 700-1000 m should be the first considered for development. 相似文献
970.
本文对吉林省中部大口钦地区营城组流纹岩进行了岩石学和地球化学研究,结果表明:流纹岩以富硅、贫钙、贫镁、贫铁为特征,在地球化学上具有典型A型流纹岩特征。在痕量元素组成上,富集LREE和LILE元素(如K、Rb、Th、U),亏损HREE和HFSE元素(如P、Ti),具强烈的负Eu异常。其原始岩浆来源于下地壳的部分熔融,形成于滨太平洋板块俯冲引起的加厚岩石圈拆沉后的伸展环境。 相似文献