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991.
甘肃省龙首山牛角沟铀矿点钾钠混合交代作用研究 总被引:1,自引:0,他引:1
牛角沟铀矿点是甘肃省龙首山铀成矿带中段东部重要的钠交代型铀矿点,该矿点外围新发现的钾钠混合交代花岗岩在该区难得一见。为更细致的解析钾钠混合交代作用,本文从岩石学、矿物学、地球化学、同位素年代学等方面开展研究,认为牛角沟中粗粒花岗岩是早古生代(445.2±7.8Ma)祁连山—龙首山造山作用晚期,后碰撞伸展环境中产出的中硅、富碱弱过铝、低铁和钙而贫钛、镁、磷的高钾钙碱性花岗岩。钾钠混合交代作用形成蚀变岩从中心向外依次为孔洞状钾钠混合交代花岗岩→雪花状方解石化钾钠混合交代花岗岩→少石英无暗色矿物紫红色钾钠混合交代花岗岩→假象绿泥石化花岗岩逐渐过渡为正常花岗岩。钾钠混合交代作用的热液溶蚀萃取了流经花岗岩中的SiO2、TiO2、FeO、Fe2O3、MnO、MgO、CaO和P2O5,以及REE、Ba、Sr、Zr、Sc、Cr、Sr、Co、Mo、Hf、Bi、Sb、Pb等化学组分,迁入孔洞状钾钠混合交代花岗岩中的组分有Na2O、K2O、MnO、Th、U、Rb、Nb、Ta、W、Sr等。CaO、MnO、Na2O、Th、U、Nb、Ta、Rb、HREE等组分与方解石一起迁入雪花状方解石化钾钠混合交代蚀变带中,而TiO2、FeO、Fe2O3、MgO、CaO、P2O5、V、U、Se、Zr等化学组分在紫红色钾钠混合交代花岗岩中析出富集。钾钠混合交代花岗岩性脆、易碎、多孔、“疏松”,为之后钠交代铀成矿作用提供了良好的围岩基础。其侵位时代进一步印证了龙首山钠交代型铀矿成矿作用起始于444~442Ma前后的可靠性。 相似文献
992.
《Sedimentology》2018,65(5):1631-1666
Detailed logging and analysis of the facies architecture of the upper Tithonian to middle Berriasian Aguilar del Alfambra Formation (Galve sub‐basin, north‐east Spain) have made it possible to characterize a wide variety of clastic, mixed clastic–carbonate and carbonate facies, which were deposited in coastal mudflats to shallow subtidal areas of an open‐coast tidal flat. The sedimentary model proposed improves what is known about mixed coastal systems, both concerning facies and sedimentary processes. This sedimentary system was located in an embayed, non‐protected area of a wide C‐shaped coast that was seasonally dominated by wave storms. Clastic and mixed clastic–carbonate muds accumulated in poorly drained to well‐drained, marine‐influenced coastal mudflat areas, with local fluvial sandstones (tide‐influenced fluvial channels and sheet‐flood deposits) and conglomerate tsunami deposits. Carbonate‐dominated tidal flat areas were the loci of deposition of fenestral‐laminated carbonate muds and grainy (peloidal) sediments with hummocky cross‐stratification. Laterally, the tidal flat was clastic‐dominated and characterized by heterolithic sediments with hummocky cross‐stratification and local tidal sandy bars. Peloidal and heterolithic sediments with hummocky cross‐stratification are the key facies for interpreting the wave (storm) dominance in the tidal flat. Subsidence and high rates of sedimentation controlled the rapid burial of the storm features and thus preserved them from reworking by fair‐weather waves and tides. 相似文献
993.
The application of seismic sedimentology in studying different sedimentary facies and reservoirs
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Seismic sedimentology,which includes seismic geomorphology and seismic lithology,has wide application prospect. Based on investigations of three different depositional environments,i.e.,siliciclastics in the Karamay Formation of Mahu sag,carbonates rock in the Longwangmiao Formation of Central Sichuan Basin,and mixed sediments in the Jialingjiang Formation of Central Sichuan Basin,the paper discussed the application of seismic sedimentology in studying facies and reservoir in three systems,i.e.,siliciclastics,carbonates,and mixed lithologies(evaporates,carbonates,and siliciclastics). It is found that alluvial fan and fluvial river facies developed in the Karamay Formation. Reservoir in point-bar has a better porosity,permeability,and higher production than that in lower-fan. Sedimentary facies in the Longwangmiao Formation are controlled by syn-depositional strike-slip faults. Thick dolostone reservoir is located mainly on the upper slope area in Moxi structure. Lower part of second member of the Jialingjiang Formation in Central Sichuan Basin changes from non-marine facies in the southwest to mixed facies and restricted evaporite facies in the middle,and to marine faces in the northeast. Reservoir-bearing dolostone lithofacies are located near the middle evaporite facies. Besides of the typical phase rotation,strata slice,and frequency decomposition,two new techniques(principal component analysis and RGB blending)were applied to these three cases. The results are satisfactory,and it is proved that seismic sedimentology is effective to qualitatively reconstruct depositional facies and quantitatively predict reservoir. 相似文献
994.
Hilary P.M. Winchester 《The Professional geographer》1999,51(1):60-67
A mixed method approach was adopted to study the experiences of lonefathers, using a classic triangulation approach of interview and questionnaire data. This study utilised an empirical realist framework of scientific enquiry, with the ‘soft’ individual interview data seen as an adjunct to the ‘hard’ aggregate quantitative methods. A review of this study found that the interviews worked well as a pilot study in a classic mixed methods framework. The questionnaires provided a range of information about thecharacteristics of this group of lone fathers, but it was the interviews which provided astonishing depth on the causes of marital breakdown and post-marital conflict, and on the discourses and other structures which sustain social processes. In this study, the interview techniques could have been used differently, in a different framework of analysis (that of critical rather than empirical realism) without the support of other mixed methods. 相似文献
995.
996.
T. Sugita Y. Kondo M. Koike M. Kanada N. Toriyama H. Nakajima T. Deshler R. Imasu 《Journal of Atmospheric Chemistry》1999,32(1):183-204
A new balloon-borne optical particle counter has been developed to make in situ measurements of stratospheric aerosols. The intensity of light scattered at 60° from the forward direction by individual particles is measured. Aerosol number concentrations in seven size channels can be inferred. The counter has been calibrated using polystyrene and polyvinyl toluene latex spheres. There is good agreement between measured and calculated individual pulse intensities for aerosol with radii from 0.16 to 2.6 µm. The size resolution is limited by broadening of the pulse count/pulse height spectrum, arising mainly from the photoelectron statistics of photomultipliers. Stratospheric aerosol measurements have been made using this instrument at Kiruna (68°N, 21°E), Sweden, in February 1995, and at Aire sur l'Adour (44°N, 0°W), France, in 1992, 1993, and 1994. The uncertainties in the measurements are discussed. The retrieved aerosol concentrations and size distributions are presented, and shown to be broadly consistent with measurements made by the University of Wyoming optical particle counter. 相似文献
997.
强夯时地基土的应力场分布特征及应用 总被引:19,自引:6,他引:13
在前期研究工作的基础上,利用积分变换技术和传递矩阵法对强夯时地基土的应力场分布特征进行了数值模拟,并和前人的数值分析与室内外试验结果进行了对比分析,结果表明:所得的动应力衰减规律与实测结果较为吻合。在动荷载作用下,地基土动应力衰减率比强夯冲击荷载作用下的衰减率快,强夯冲击荷载作用下的最大动应力等值线图可作为估算强夯的有效加固深度和加固范围时参考。 相似文献
998.
999.
The dynamic analysis of progressive collapse faces a great number of obstacles that often lead to the collapse of the analysis prior to the actual analysis of collapse. Hence, the Mixed Lagrangian Formulation that has been shown to be very robust was adopted as a framework to accommodate such analysis. By modifying the loading function and the numerical scheme, the capabilities of this framework were extended to account for strength degradation and fracture, while some insight to its behavior is introduced as well. The examples presented show a very robust and stable behavior of the numerical scheme in terms of the time step size required, even in cases where a sudden fracture takes place. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
1000.