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981.
Primary pores are undeveloped in the granite, but multiple types of reservoir spaces can form during the processes of weathering and tectonic movement. Taking Penglai (PL) oil field as an example, the vertical zonal characteristic of the buried granite is defined and the relationship between different zones and reservoir is discussed. The granite can be divided into weathered zone (WZ) and bedrock zone (BZ) vertically according to weathered or not, and the WZ can be divided into weathered clay zone (WCZ), weathered glutenite zone (WGZ), and weathered fracture zone (WFZ) further. The lithology, mineral composition, and weathering indices (geochemistry) can distinguish different zones. Both WZ and BZ can form good reservoirs, among them the reservoir of WGZ is dominated by pores, while that of WFZ and the BZ are mainly composed of fractures, and they constitute the high-quality reservoir together. There is an obvious positive correlation between the thickness of fracture zone in BZ and the thickness of WZ, and both WZ and BZ are influenced by tectonic movement. Moreover, WZ superimposed with meteoric water dissolution makes it the best reservoir in the granitic buried hill, and the development of fractures in BZ extends the thickness of reservoir greatly. 相似文献
982.
Huapeng Niu Xiaoqin Jiao Qingbin Xie Yongshu Zhang Xin Li Zhixiong Wu Bo Wang Xin Yang Yanan Li Zijie Gao 《Geological Journal》2020,55(12):7613-7637
The South Altyn Block (SAB), located along the southern margin of the Altyn Tagh in Qaidam Basin, has a significant relationship with the tectonics of the Qaidam Basin basement. This study presents the petrological features, geochemical compositions, and zircon U–Pb and Hf isotope data of four granitic plutons from the eastern segment of the SAB to constrain the petrogenesis and tectonic setting of this region during the Palaeozoic. Basing on previous U–Pb dating results, the zircon U–Pb analysis in this study suggests that Palaeozoic magmatic events can be subdivided into four episodes: Late Cambrian (approximately 502 Ma), Late Ordovician (approximately 444 Ma), Early Devonian, and Middle Permian (approximately 271 Ma). The Palaeozoic granitoids were derived mainly from Neoproterozoic juvenile crustal components, with minor palaeoproterozoic ancient materials. The S- and I-type granitoids in Late Cambrian indicate a compressional tectonic environment with respect to subduction, and A-type granitoids suggest post-collision regime. The Late Ordovician granodiorites of A-type imply typical magmatism within a post-collision extensional setting. Ascribing to the subduction of Palaeo-Tethys Ocean during the Devonian, S-type granites were emplaced in the Early Devonian accompanied with the crust thickening. The Middle Permian magmatic events include a series of S-type granitoids, demonstrating the setting of oceanic subduction along with the closure of the Palaeo-Tethys Ocean. 相似文献
983.
984.
Qiqi Xue Yaoling Niu Shuo Chen Pu Sun Meng Duan Yajie Gao Di Hong Yuanyuan Xiao Xiaohong Wang Pengyuan Guo 《Geological Journal》2020,55(1):173-196
We present the results of our study on 16 Cretaceous granitoid plutons along the south-east coast of continental China. The zircon U–Pb ages and the bulk-rock Rb–Sr isochron age (R2 = 0.935) indicate that the granitoids represent the last episode of magmatism (119–92 Ma) associated with the paleo-Pacific Plate subduction beneath continental China. These granitoids show large compositional variation that is to a first-order consistent with varying extents of magma evolution, which is best expressed by a large SiO2/MgO range and correlated trends of SiO2/MgO with the abundances and ratios of major and trace elements. The correlated Nd (εNd(t) = −6.1 to −1.2) and Hf (εHf(t) = −4.7 to +3.4) isotopic variation reflects parental magma compositional differences as a result of varying sources and processes. The Nd–Hf isotope data indicate that these granitoids were produced by mature continental crust melting with significant mantle input (~20–60%). Rhyolite-MELTS modelling shows that relative to the less evolved (i.e., low SiO2/MgO) granitoid plutons, the progressively more evolved (i.e., varying larger SiO2/MgO) plutons can be explained by varying extents (~24% to 67%) of fractional crystallization. The origin of the magmas parental to the granitoids is best explained by a two-stage process: (a) subducting slab dehydration-induced mantle wedge melting for basaltic magmas and (b) ascent and underplating/intrusion of the basaltic magmas caused the mature crustal melting for the granitoid magmas. The systematic northward decrease in εNd(t) and εHf(t) suggests progressively more enriched crustal material towards the north, but it may very well indicate northward crustal thickening, permitting a greater extent of crustal assimilation. 相似文献
985.
Pan-Pan Niu Shao-Yong Jiang Qi-Sheng Hu Tian-liang Xu Suo-Fei Xiong 《Geological Journal》2020,55(2):1563-1586
The Wangjiadashan Cu–Au deposit is a vein-type deposit controlled by the secondary faults of the Wushan Fault zone in the Suizao area of Hubei Province. Three hydrothermal stages are identified, namely, (I) barren quartz stage, (II) the quartz-sulphide stage, and (III) quartz-carbonate stage. Six types of fluid inclusions occur in quartz: (a) liquid-rich aqueous fluid inclusions (L + V), (b) vapour-rich aqueous-carbonic fluid inclusions (V + L), (c) water-rich aqueous-carbonic fluid inclusions (L + V + CO2), (d) CO2-rich aqueous-carbonic fluid inclusions (V + L + CO2), (e) pure carbonic fluid inclusions (pure CO2), and (f) daughter mineral-bearing multiphase inclusions (S-type) with three subclasses (S1, S2, and S3 subtype). Two types of fluid inclusions occur in calcite: (a) liquid-rich aqueous fluid inclusions (L + V) and (b) pure carbonic fluid inclusions (pure CO2). The S-type fluid inclusions include halite (NaCl), calcite (CaCO3), and chalcopyrite (CuFeS2). The fluid system is composed of CO2–NaCl–H2O. The homogenization temperatures of the three stages are 295°C to 390°C, 245°C to 280°C, and 200°C to 241°C, with salinities of 7.3–19.8 wt% NaCl equiv. (except for several high values of 33.8 to 44.3 wt% NaCl equiv.), 7.7–13.7 wt% NaCl equiv., and 5.6–10.1 wt% NaCl equiv., respectively. Fluid immiscibility occurred in stage I that accounts for the high-salinity fluids, but the dominant ore precipitation occurred afterward during temperature drop. In situ sulphur isotope analysis indicates a δ34S value around 0 (+1.1% to +2.2%) for the chalcopyrite, suggesting that the sulphur likely derived from the deep-seated magma. Pyrites show δ34S values from −0.5‰ to +6.5‰ in stage II, from +0.7‰ to +6.6‰ in country rock of marble, but significantly higher from +12.8‰ to +21.7‰ in country rock of greenschist. These results indicate the sulphur for pyrite in stage II likely derived from the mixing of deep-seated magma and country rocks. From stages I to II, a slightly increase of δD (from −86‰ and −73‰ to −59‰ and −56‰) and a decrease of δ18O (from 8.9‰ and 7.1‰ to 1.3‰ and 3.4‰) indicate that an increasing involvement of meteoric water. The carbon isotopes of fluid inclusions CO2 in quartz of stage I (−11.0‰ to −13.0‰) indicate a major magmatic or metamorphic carbon source mixed with minor sedimentary sourced carbon, but a major organic carbon source (−32.0‰ to −35.0‰) for stage II fluids. In conclusion, the Wangjiadashan Cu–Au deposit belongs to the orogenic type. 相似文献
986.
针对致密砂岩气储层复杂的微观孔隙结构进行岩石物理建模,在模型中比较了单一孔隙纵横比、双孔隙模型两种表征孔隙结构的表征方式。岩石物理正演分析表明,两种孔隙结构模型均可解释致密砂岩复杂的速度-孔隙度关系。岩石物理反演结果表明,双孔隙模型对测井横波速度的预测精度更高,说明该模型更适用于表征研究区致密砂岩的孔隙结构,反演的软孔比例参数能够反映地层中孔隙结构的非均匀分布。应用双孔隙模型计算致密砂岩地层岩石骨架的弹性模量,与Krief及Pride等传统经验公式相比,该方法考虑了岩石骨架模量与矿物基质、孔隙度和孔隙结构等微观物性因素的关系,理论上更具有严谨性。对致密砂岩骨架模量计算结果的分析表明,少量微裂隙的存在即能够显著影响致密砂岩骨架的弹性性质,同时孔隙空间中的球形孔隙是致密气的主要赋存空间。并且,通过致密砂岩骨架弹性模量,进一步计算了可用于地层评价的Biot系数等岩石物理参数。致密砂岩骨架模量的预测结果可为Gassmann流体替换理论、BISQ孔隙弹性介质理论等岩石物理方法提供关键参数。 相似文献
987.
当前洪水风险分析按照典型设计标准洪水进行计算的模式难以满足实际防洪管理需要,为了提高洪水风险分析的实时性以及适应洪水演进的动态性,设计了动态实时洪水风险分析框架。在本框架中,先采用一维和二维动态耦合水动力学数值方法耦合溃堤模型,然后在樵桑联围防洪保护区建立洪水演进模拟模型,通过灵活处理模型计算边界条件以及动态设置溃堤功能,计算不同设计标准洪水发生时,堤防出现单一溃口或者组合溃口后保护区内洪水演进过程。按照上述框架开发了樵桑联围动态实时洪水风险图编制与管理应用系统,并利用历史洪水资料开展模型验证,验证结果表明,2008-06洪水马口站、三水站、大熬站、甘竹（一）站的实测最高水位和模型计算最高水位的绝对误差分别为-0.10、0.10、0.09、0.04 m,均满足洪水模拟精度要求。利用模型计算了西江发生200年一遇的洪水情况下,江根堤防出现溃口后的洪水流量及溃口内外洪水水位变化过程,模拟溃口宽度168 m,最大溃口洪水流量达到5 190 m3,分析了堤防溃决后3、6和24 h洪水漫延导致村落淹没情况,结果表明其满足合理性分析。 相似文献
988.
Wen-hui Jie Chun-lei Xiao Ce Zhang En Zhang Jing-yue Li Bing Wang Hai-wei Niu Shuang-fa Dong 《China Geology》2021,4(2):353-363
The environmental change in the wetlands in the southern Mongolian Plateau has important impacts on the environment of North China and even the entire Northeast Asia, from which the global climate change can be understood on a large scale, especially the climate change in the Mongolian Plateau. This study extracted the information on the wetlands from three stages of remote sensing images (also referred to as RS images) of the study area, including Enhanced Thematic Mapper Plus (ETM+) images of 2000, TM images of 2010, and Landsat 8 Operational Land Imager (OLI) images of 2018. As indicated by the extraction results, the area of wetlands decreased from 796.90 km2 of 2000 to 666.24 km2 of 2018 at a rate of 7.26 km2/a. The reduced area is 130.66 km2, which is about 16.4% reduction. And the patch number of wetlands decreased from 731 of 2000 to 316 of 2018 in the study area, approximately 56.8% reduction (415 patches), and the decrease in the area of the wetlands mainly occurred in the northwest endorheic region. In terms of wetland types, the change of the wetlands was dominated by the decrease of lacustrine wetlands, of which the area and patch number decreased by 106.2 km2 and 242, respectively. Furthermore, the area of the lacustrine wetlands decreased at the highest rate of 8.70 km2/a in 2010–2018. From the perspective of spatial distribution, the wetlands in the western part shrunk more notably than those in the eastern part as a whole in the study area. According to local meteorological data, the precipitation gently decreased and the temperature increased (about 1.7°C) from 1975–2018. Overall, the decrease in the area of the wetlands and the temperature rises in the study area were mainly driven by the Mongolian monsoon climate, reduction in precipitation, and human activities. 相似文献
989.
J. W. Ge X. T. Zhang B. G. Jones F. S. Yu Z. C. Niu 《Australian Journal of Earth Sciences》2017,64(7):931-956
The structural evolution and stratigraphic architecture of the Southern Lufeng Depression in the Pearl River Mouth Basin, South China Sea show two second-order sequences (SSQ1 and SSQ2) and nine third-order sequences (WSQ1-5 and ESQ1-4) within the Eocene rift-related successions. Based on integrated interpretations of seismic reflections, well logs and core data, five distinct tectono-stratigraphic patterns are identified: (1) the initial synrift-I sequence (WSQ1) of low tectonic subsidence, overfilled by alluvial fan or fan-delta deposits and volcanic deposits, with no clear systems tracts; (2) the climax synrift-I sequences (WSQ2–4) developed in response to rapid tectonic subsidence, generally consisting of a low-stand systems tract (LST), transgressive systems tract (TST) and high-stand systems tract (HST); (3) the late synrift-I sequence (WSQ5) characterised by a decreased tectonic subsidence rate, dominated by braided delta, deep and shallow lacustrine sediments, mainly constructed by TST and HST; (4) the early synrift-II sequences (ESQ1–2) rapidly filled by braided deltaic sandstone and mainly composed of TST and HST with less common LST units; and (5) the late synrift-II sequences (ESQ3–4), which are totally filled by braided deltaic system in a shallow-water lake setting, presenting typical imbricate clinoforms or sub-parallel seismic configurations, consisting of only TST and HST components. During the climax stage of synrift-I development, the depositional setting changed from a prominent shallow lake (WSQ2) to a deep-lucustrine with turbiditic deposits (WSQ3) and finally dominated by mostly braided deltaic-shallow lacustrine deposits (WSQ4); the HST occupies an increasing proportion from early to late. Furthermore, the stratigraphic patterns, especially LST units of the climax synrift-I stage, are significantly influenced by topographic variations and slope-break belt types in the hanging dip-slope. This study reveals that the spatial and temporal evolution of lacustrine depositional and stratigraphic patterns were significantly controlled by the interplay of tectonic subsidence and sediment supply, and provides a fundamental basis for predicting the favourable reservoirs and geometry of source rocks related to the general variability of Eocene rift-related tectonic subsidence in the Southern Lufeng Depression of the Pearl River Mouth Basin. Furthermore, the topographic responses of differential active fault-stepped patterns associated with magma intrusions, highlight the variability of relevant sequence architectures in the hanging dip-slope in lacustrine rift basins. 相似文献
990.
This paper studies the coherent modes of multi‐scale variability of precipitation over the headwater catchments in the Pearl River basin in South China. Long‐term (1952–2000) daily precipitation data spatially averaged for 16 catchments in the basin are studied. Wavelet transform analysis is performed to capture the fluctuation embedded in the time series at different temporal timescales ranging from 6 days to 8.4 years. The catchment clusters of the coherent modes are delineated using the principal component analysis on the wavelet spectra of precipitation. The results suggest that as much as 98% of the precipitation variability is explained by only two coherent modes: high small‐scale mode and high seasonal mode. The results also indicate that a large majority of the catchments (i.e., 15 out of 16) exhibit consistent mode feature on multi‐scale variability throughout three sub‐periods studied (1952–1968, 1969–1984, and 1985–2000). The underlying effects of the coherent modes on the regional flood and drought tendency are also discussed. 相似文献