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笔者等对周潭群沉积变质岩及其中脉体的微量元素、氧同位素地球化学进行了研究,结果表明,变质石英脉继承了其围岩的稀土元素及氧同位素地球化学特征,表明形成石英脉的流体来源于围岩;脉体的微量元素对Zr-Hf、U-Th、Nb-Ta和Y-Ho与变质岩有一定的差异,且有一定的分异,指示脉体是流体作用的产物。变质流体通过侧向扩散作用形成了周潭群变沉积岩中的变质脉体。 相似文献
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Ruarri J. Day-Stirrat Kitty L. Milliken Shirley P. Dutton Robert G. Loucks Stephen Hillier Andrew C. Aplin Anja M. Schleicher 《Marine and Petroleum Geology》2010
Wilcox Group mudstones have been mechanically and geochemically transformed over a temperature range of 20–200 °C. Our research controlled for provenance and age by sampling from five wells, parallel to the paleodepositional axis, all within the Houston delta system. Across the sampled depths, mudstone porosity has been reduced from ∼25 to <10% and bulk mineralogical change as documented by quantitative X-ray diffraction includes decreases in quartz, K-feldspar and kaolinite content whereas illite + illite − smectite, chlorite, and plagioclase increase. These mineral transformations transfer elements at a scale of less than 1 mm from one mineralogical form to another, however, X-ray fluorescence data suggest that among major elements only Al2O3 and TiO2 are fully conserved within the system (trace-element ZrO2 is also conserved). K2O has been added to and SiO2 released from the Wilcox Group mudstones. Cathodoluminescence and secondary electron imaging did not find this SiO2 locally precipitated. We, therefore, document an open-system geochemical behavior. 相似文献
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地理信息公共服务平台的用户分类及服务分类 总被引:2,自引:1,他引:1
地理信息技术的发展经历了集中式、模块化、组件化的过程,目前正向地理信息的Web服务方向发展。传统的集中式地理信息系统中,功能的分类决定了用户的分类;而在地理信息服务的架构中,用户的分类导致服务的分类及其与用户分类的映射。本文从地理信息服务的架构出发,分析并提出了面向服务的地理信息公共服务的用户群分类与对应的服务分类,为地理信息公共服务平台的构建和地理信息服务资源的有效组织和整合提供理论依据。 相似文献
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辽宁省是我国重要的金矿产地之一。省内金矿可划分为岩浆热液型、陆相火山岩型、同韧性剪切变质热液型、变质—岩浆热液叠生型、砂砾岩型及河相冲积型(砂金矿)六种类型。金矿的形成与特定的地层、构造、岩浆岩密切相关。稳定同位素资料表明,金矿的成矿物质主要来源于古老的结晶基底——太古宙变质杂岩(第一矿源层)及早元古宙中浅变质岩(衍生矿源层);含矿热液主要为岩浆水,变质水和大气水,且多为两种水的混合物;大气水在成矿作用中占有重要地位。金矿的成矿演化经历了太古代-早元古代矿源层及同韧性剪切变质热液金矿床、晚三叠纪-燕山早期岩浆热液及叠生型矿床及燕山晚期陆相火山岩型矿床三个形成阶段。 相似文献
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The lower part of the Old Red Sandstone in the Dingle Penisula has been previously assigned to one lithostratigraphic group (Dingle Group) despite marked variations in sedimentary facies. However the apparently oldest non-marine sequence in the northwest of the peninsula has sedimentary and lithological attributes that contrast strongly with those of the late Silurian-early Devonian Dingle Group to the south. This northern sequence, here renamed the Smerwick Group, evolved independently of the Dingle Group in a separate basin of deposition. Field relationships between the two groups in the north of the peninsula are interpreted as indicating that the Smerwick Group overlies, with angular unconformity, a normal Dingle Group succession. Similarly, it is argued that the Smerwick Group overlies, with angular unconformity, the Dingle Group in the northwest of the peninsula, but there the Dingle Group is attenuated, represented only by a conglomerate unit some 10 m thick. In the absence of biostratigraphic evidence the age of the Smerwick Group is poorly constrained. Nevertheless, we propose a tectonic model that suggests that the Smerwick Group evolved within a small extensional half-graben on the northern margin of the Munster Basin. This model accounts for the stratigraphic and structural relationships observed, and implies that the Smerwick Group is of Late Devonian age. 相似文献
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The Matt Wilson structure is a circular 5.5 km-diameter structure in Early Mesoproterozoic or Neoproterozoic rocks of the Victoria Basin, Northern Territory. It lies in regionally horizontal to gently dipping Wondoan Hill and Stubb Formations (Tijunna Group) and Jasper Gorge Sandstone (Auvergne Group). An outer circumferential syncline with dips of 5?–?40° in the limbs surrounds an intermediate zone with faulted sandstone displaying horizontal to low dips, and a central steeply dipping zone about 1.5 km across. Several thrust faults in the outer syncline appear to indicate outward-directed forces. The central zone, marked by steeply dipping to overturned Tijunna Group and possibly Bullita Group sandstone and mudstone, indicates uplift of at least 300 m. The rocks are intensely fractured with some brecciation, and contain numerous planar to subtly undulating surfaces displaying striae which resemble shatter cleavage. Thin-sections of sandstone from the central area show zones of intense microbrecciation and irregular and planar fractures in quartz, but no melt-rocks have been identified. The planar fractures occur in multiple intersecting parallel sets typical of relatively low-level (5?–?10 GPa) shock-pressure effects. Alternative mechanisms, i.e. igneous intrusion, carbonate collapse, diapirism and regional deformation processes, have been discounted. The circular nature, central uplift, faulting, shatter features and planar fractures are all consistent with an impact origin. The Matt Wilson structure is most likely a deeply eroded impact structure in which the more highly shocked rocks of the original crater floor have been removed by erosion. Estimates of the age of the Auvergne and Tijunna Groups range from Early Mesoproterozoic (which we favour) to Late Neoproterozoic. Early Cambrian Antrim Plateau Volcanics near the impact structure show no signs of impact effects, allowing the age of impact to be constrained between Early Mesoproterozoic and Early Cambrian. The presence of widespread soft-sediment deformation features, apparently confined to a single horizon in the Saddle Creek Formation some 700?–?1000 m stratigraphically higher in the Auvergne Group than the rocks at the impact site, and apparently increasing in thickness towards the Matt Wilson structure, lead us to speculate that this probable event horizon is related to the impact event: if correct the impact occurred during deposition of the Saddle Creek Formation. 相似文献
70.
不纯碳酸盐岩的变质作用 总被引:1,自引:0,他引:1
不纯碳酸盐岩中的矿物共生组合与变质时的总压和二氧化碳分压密切相关。总压增高促使透闪石、透辉石和橄榄石等矿物生成温度增高。变质过程中岩石中流体成分的变化有两种极端情况,即渗滤作用和缓冲作用。渗滤作用下变质反应,变质矿物界线和变质矿物特征等均与缓冲作用下有所差异,以此可以区别它们。湖北宿松群和河北红旗营子群不纯大理岩是在渗滤作用下变质的。山西五台群板峪口组不纯大理岩是在缓冲加渗滤作用下变质的。 相似文献