同步辐射X射线荧光微探针技术测定太古宙条带状硅铁建造中硅质条带及包裹体的微量元素

通过对35亿年前曹庄岩组的条带状硅铁建造(BIF)的硅质条带以及石英中包裹体微量元素的分析,初步探讨了35亿年前的 BIF 形成时期海洋的化学成分。结果表明太古宙海洋中贫乏 P、V、Cu 等生命元素,限制了真核生物的发展,而其它微量元素高度富集,为化学自养细菌提供了良好的环境。在 BIF 的硅质条带的形成过程中,微量元素的含量受到磁铁矿沉积吸附的强烈控制。     

Geological and geochemical characteristics of the Baogudi Carlintype gold district(Southwest Guizhou,China) and their geological implications

The newly discovered Baogudi gold district is located in the southwestern Guizhou Province,China,where there are numerous Carlin-type gold deposits.To better understand the geological and geochemical characteristics of the Baogudi gold district,we carried out petrographic observations,elemental analyses,and fluid inclusion and isotopic composition studies.We also compared the results with those of typical Carlin-type gold deposits in southwestern Guizhou.Three mineralization stages,namely,the sedimentation diagenesis,hydrothermal(main-ore and late-ore substages),and supergene stages,were identified based on field and petrographic observations.The main-ore and late-ore stages correspond to Au and Sb mineralization,respectively,which are similar to typical Carlin-type mineralization.The mass transfer associated with alteration and mineralization shows that a significant amount of Au,As,Sb,Hg,Tl,Mo,and S were added to mineralized rocks during the main-ore stage.Remarkably,arsenic,Sb,and S were added to the mineralized rocks during the late-ore stage.Element migration indicates that the sulfidation process was responsible for ore formation.Four types of fluid inclusions were identified in ore-related quartz and fluorite.The main-ore stage fluids are characterized by an H2O–NaCl–CO2–CH4±N2system,with medium to low temperatures(180–260℃)and low salinity(0–9.08%NaCl equivalent).The late-ore stage fluids featured H2O–NaCl±CO2±CH4,with low temperature(120–200℃)and low salinity(0–7.48%Na Cl equivalent).The temperature,salinity,and CO2and CH4concentrations of ore-forming fluids decreased from the main-ore stage to the late-ore stage.The calculated δ^13C,d D,and δ^18O values of the ore-forming fluids range from-14.3 to-7.0%,-76 to-55.7%,and 4.5–15.0%,respectively.Late-ore-stage stibnite had δ^34S values ranging from-0.6 to 1.9%.These stable isotopic compositions indicate that the ore-forming fluids originated mainly from deep magmatic hydrothermal fluids,with minor contributions from strata.Collectively,the Baogudi metallogenic district has geological and geochemical characteristics that are typical of Carlin-type gold deposits in southwest Guizhou.It is likely that the Baogudi gold district,together with other Carlin-type gold deposits in southwestern Guizhou,was formed in response to a single widespread metallogenic event.     

SYNERGISTIC EFFECTS ON ATMOSPHERIC ANOMALY OF THE TROPICAL INDIAN AND PACIFIC OCEANS IN NORTHERN WINTER*

In terms of observational analysis and numerical simulations,study is performed of the synergistic effects of the tropical Indian Ocean and Pacific SSTA on the atmosphere in northern winter.It turns out that the SSTA features show in-phase variation for the Indian Ocean and the central/eastern Pacific at low latitudes and anti-phase change compared with that in the neighborhood of the western Pacific "warming pool".When negative SSTA in the western Pacific and positive SSTA in the central/eastern Pacific and the Indian Ocean are available,the 500 hPa height anomaly exhibits a wave train of a positive-negative-positive anomaly following a great-circle path emanating from the subtropical western Pacific via the NW portion to North America,with enhanced westerly jet over midlatitude East Asia and the NW Pacific,and v.v.The comparison to the results from the numerical modeling of the tropical western Pacific SSTA reveals the importance of the synergistic effects of the oceans on atmospheric circulations.     

内蒙古固阳朱拉沟基性麻粒岩T—P轨迹

本文通过对内蒙古朱拉沟基性麻粒岩的岩石学、矿物学及温度、压力等研究,建立了基性麻粒岩形成所经历的P-T轨迹,解释了基性麻粒岩形成的大地构造环境。     

东濮凹陷桥口-白庙地区砂岩石英增生及其对流体活动的反映

对东濮凹陷下第三系储层砂岩石英增生边及其中的流体包裹体进行了鉴定和检测,结果表明东濮凹陷桥口-白庙地区共有3期石英增生现象,代表3期流体活动。第1期与第2期发生在盆地深陷期,当时埋深1700～3000m,年代28～37Ma,第3期增生边尚不能确定其形成条件,但可确定其形成于碳酸盐大规模交代石英颗粒之后。桥口地区第1期所代表的流体活动温度主要在110～115℃,第2期所代表的流体活动温度主要在130～135℃。白庙地区第1期所代表的流体活动温度主要在105～110℃,第2期所代表的流体活动温度主要在120～125℃。这3期流体活动的性质可能是粘土矿物转化过程中释放的晶格水通过泥岩的幕式压裂作用向砂岩中释放的结果。     

利用概率密度分布提取流体观测资料中的高频异常信息——以2008年汶川8.0级地震为例

随着地下流体观测技术的提高,尤其是地下流体观测数字化改造以后,观测资料的采样频率明显提高,这些高频采样的观测资料中蕴含着丰富的构造信息,如何从分钟值甚至更高频率采样的观测资料中提取有用的异常信息,是目前从事地震地下流体资料分析人员最为关注的科学问题之一.本文引入概率密度分布法,分析了2008年汶川8.0级地震前南北地震带及其附近区域72个测点的数字化水位和水温分钟值采样高频观测资料,结果显示:汶川8.0级地震前有16个测点水位和14个测点水温出现高频异常信息,出现高频信息异常的观测点多集中在滇西南构造带,异常出现的时间呈现出由南向北推移的特征.据此认为概率密度分布法在流体资料的高频异常信息提取方面具有一定的可靠性与适用性,可为数字化高频观测资料异常提取提供借鉴.     

P-T-t Path of Mafic Granulite Metamorphism in Northern Tibet and Its Geodynamical Implications

Mafic granulites have been found as structural lenses within the huge thrust system outcropping about 10 km west of Nam Co of the northern Lhasa Terrane, Tibetan Plateau. Petrological evidence from these rocks indicates four distinct metamorphic assemblages. The early metamorphic assemblage (M1) is preserved only in the granulites and represented by plagioclase+hornblende inclusions within the cores of garnet porphyroblasts. The peak assemblage (M2) consists of garnet+clinopyroxene+hornblende+plagioclase in the mafic granulites. The peak metamorphism was followed by near-isothermal decompression (M3), which resulted in the development of hornblende+plagioclase symplectites surrounding embayed garnet porphyroblasts, and decompression-cooling (M4) is represented by minerals of hornblende+plagioclase recrystallized during mylonization. The peak (M2) P-T conditions of garnet+ clinopyroxene+plagioclase+hornblende were estimated at 769-905℃ and 0.86-1.02 GPa based on the geothermometers and geobarometers. The     

考虑超固结效应的不同温度路径下饱和粉质黏土的热固结

通过室内试验,研究了超固结比OCR对不同温度路径下中空圆柱饱和粉质黏土热固结特性的影响。研究表明,同一升温过程、不同超固结比试样所产生的最大孔压基本相同,但在相同的降温过程中,随着OCR的增大,产生的负孔压的绝对值有增大的趋势;升温或降温过程产生的体应变随着OCR的增大而减小,呈指数形式变化,并且温度幅度越大,这种变化幅度也越大;经过升温-降温过程后的最终体应变也随着OCR的增大而减小;升温或降温到同一温度值,其过程设置的温度等级越多,固结体应变也越大,并且随着OCR的增大,不同等级之间的体应变差值减小,而OCR对不同等级升温-降温后的最终体应变间的差值影响较小。     

基于典型事例推理的路径规划方法研究

Case-based reasoning is an AI technique in which the previous solutions are stored for future use. People are used to guiding themselves according to those routes that are stored in their memories and have been used by them before. It is just based on people’s preference to familiar routes, which are gained through the study of the cognitive activities. We propose to apply the intelligent method based on the case reasoning to path planning. It is impossible for a case base to store all the solutions to all the shortest paths; therefore, part of them should be stored. However, which routes should be stored and which should not be? How do we adapt the cases that have already been stored and how do we acquire the shortest route based on them? All these issues need to be explained by integrating knowledge of the network on account of case-based reasoning techniques. This paper suggests the case-based reasoning in another point. This means finding some irreplaceable links on the basis of the complete analysis of the problems space, which are called the must_be_passed link between the source and destination. Merely compute the shortest path case from those best exit/entry nodes of the grids to the irreplaceable links, and then add them into the case base storing for future use. This method is based on case-based reasoning technique and completely considers the properties of the problem space. In addition to the use of knowledge of the natural grid in the route network, this method is more efficient than existing algorithms on computing efficiency.     

P-T conditions of quartz-calcite boudins and vein formation within a low-angle detachment fault in Tinos Island (Aegean Sea): a fluid-inclusion study

Fluid inclusions were investigated in successive generations of quartz-calcite boudins and veins in the vicinity of, and within, the low-angle detachment fault (of Early Miocene age) exposed on Tinos Island (Cyclades, Greece). Abundant boudins, veins, tension gashes and mineral segregations were formed during various stages of ductile and brittle shear along the detachment indicating fluid flow at various crustal levels, assisted motion and slip along the detachment. Three generations of fluid inclusions were identified: (1) syn-deformation aqueous inclusions; (2) local- late-deformation H₂O-CO₂ inclusions; (3) post-slip deformation, partly decrepitated aqueous and H₂O-CO₂ inclusions. The conditions of inclusion trapping correspond to the greenschist facies, at temperatures between 300 and 450°C and pressures in the range of 1.5–4.0 kb. A gradient of pressure of about 0.5 kb from the fault zone to the rocks of upper and lower plates is suggested. The results indicate that the syn-deformation fluid was NaCl-KCl-sulfate-dominated with a salinity of about 5 wt% NaCl equiv. Downward infiltration of meteoric water is a suitable source for this fluid. During the late stage of fault activity, in the brittle field, fluid was of H₂O-CO₂ composition. Very rapid exhumation of the entire section (unrelated to motion on the investigated fault) is marked by numerous decrepitation clusters of the fluid inclusions.