A 3.5 Ga record of water-limited, acidic weathering conditions on Mars

The secondary mineral budget on Earth is dominated by clay minerals, Al-hydroxides, and Fe-oxides, which are formed under the moderate pH, high water-to-rock ratio conditions typical of Earth's near-surface environment. In contrast, geochemical analyses of rocks and soils from landed missions to Mars indicate that secondary mineralogy is dominated by Mg (± Fe, Ca)-sulfates and Fe-oxides. This discrepancy can be explained as resulting from differences in the chemical weathering environment of Earth and Mars. We suggest that chemical weathering processes on Mars are dominated by: (1) a low-pH, sulfuric acid-rich environment in which the stoichiometric dissolution of labile mineral phases such as olivine and apatite (± Fe–Ti oxides) is promoted; and (2) relatively low water-to-rock ratio, such that other silicate phases with slower dissolution rates (e.g., plagioclase, pyroxene) do not contribute substantially to the secondary mineral budget at the Martian surface. Under these conditions, Al-mobilization is limited, and the formation of significant Al-bearing secondary phases (e.g., clays, Al-hydroxides, Al-sulfates) is inhibited. The antiquity of rock samples analyzed in-situ on Mars suggest that water-limited acidic weathering conditions have more than likely been the defining characteristic of the Martian aqueous environment for billions of years.     

Late Quaternary clay minerals off Middle Vietnam in the western South China Sea: Implications for source analysis and East Asian monsoon evolution

High-resolution clay mineral records combined with oxygen isotopic stratigraphy over the past 450 ka during late Quaternary from Core MD05-2901 off Middle Vietnam in the western South China Sea are re-ported to reconstruct a history of East Asian monsoon evolution. Variations in Illite, chlorite, and kaolinite contents indicate a strong glacial-interglacial cyclicity, while changes in smectite content present a higher frequency cyclicity. The provenance analysis indicates a mixture of individual clay minerals from various sources surrounding the South China Sea. Smectite derived mainly from the Sunda shelf and its major source area of the Indonesian islands. Illite and chlorite originated mainly from the Mekong and Red rivers. Kaolinite was provided mainly by the Pearl River. Spectral analysis of the kaolin-ite/(illite chlorite) ratio displays a strong eccentricity period of 100 ka, implying the ice sheet-forced win-ter monsoon evolution; whereas higher frequency changes in the smectite content show an ice sheet-forced obliquity period of 41 ka, and precession periods of 23 and 19 ka and a semi-precession period of 13 ka as well, implying the tropical-forced summer monsoon evolution. The winter monsoon evolution is generally in coherence with the glacial-interglacial cyclicity, with intensified winter monsoon winds during glacials and weakened winter monsoon winds during interglacials; whereas the summer monsoon evolution provides an almost linear response to the summer insolation of low latitude in the Northern Hemisphere, with strengthened summer monsoon during higher insolation and weakened summer monsoon during lower insolation. The result suggests that the high-latitude ice sheet and low-latitude tropical factor could drive the late Quaternary evolution of East Asian winter and summer monsoons, respectively, implying their diplex and self-contained forcing mechanism.     

低渗致密砂岩气田储层损害评价及保护措施

储层孔隙类型、孔隙结构、粘土矿物类型和含量等是造成气层受伤害的潜在因素 ,而外来固相、滤液以及生产或作业压差、生产时间等工程因素也可造成或加重对气层的伤害程度 ,因此 ,低渗致密气田 (藏 )的开发效果在很大程度上依赖于开发技术水平的提高。应用岩心评价实验、时间推移测井、生产测井以及试井等方法 ,评价了河南东濮凹陷白庙、文 2 3等气田低渗致密砂岩储层的敏感性及与外来液的配伍性 ,分析了导致或加重对气层造成伤害的工程因素。在气田开发的全过程中 ,有针对性地制定出对气层进行保护的配套措施 ,减少了对储层的伤害 ,充分发挥了气层的潜力 ,提高了气田的开发效果 ,也为同类气田提供了借鉴。     

西安地区黄土含水率变化特点

通过对西安地区黄土剖面的野外观察、颗粒分析和含水率的测定 ,系统地研究了黄土层含水率的变化特点 ,初步认识到在同一黄土剖面上 ,黄土含水率从上到下呈波动变化 ,其峰值位于古土壤层内 ,而波谷处于黄土层内 ,并呈波动增加的趋势。在具有结核层的黄土层中 ,其含水率从上部到下部呈由大变小再变大的趋势 ,其峰值位于结核层之上 ,CaCO3 结核层具有隔水作用 ;在古土壤层中 ,从上向下 ,其含水率呈由小变大再变小的规律 ,其峰值出现在古土壤的中、下部位 ,即粘土化最强的部位。土壤质地是决定含水率大小的重要因素 ,在包气带中 ,黄土含水率的变化与粘土颗粒含量具有明显的正相关关系。     

凯里地区红粘土的工程特性与评价

凯里地区红粘土是一种较好的建筑物地基土，它除具有一般红粘土的通性外，其最大的特点是胀缩性小，塌陷概率低，如果对它做出客观的工程地质评价并加以利用将会产生重大的经济效益。     

离层注浆防治地表塌陷的注浆量计算

地下煤层的大量开采，引起采空空间向地面的转移从而导致地表塌陷，造成危害。基于岩体中离层产生、发展的研究理论，提出利用“离层注浆防治地表塌陷技术”以控制地表塌陷。注浆量和与其相应的泵压是覆岩离层注浆工程实施防治地表塌陷成功与否的关键参数之一。通过对注浆机理及浆液流动模式的简论，给出了注浆量的两种计算方法并引入几个重要参数。文章指出了与计算所得注浆量相匹配的泵压，且给出一个在理论指导下的选型实例，为现场施工设计提供了理论依据。     

北衙红色粘土型金矿地质特征和成矿条件

本文系统研究了北衙红色粘土型金矿的地质特征和矿床类型，并从金矿产出的地质背景入手，分析其形成条件，认为是本区很有代表性的一种新的金矿类型，对矿区增储和区域找矿具有重大意义。     

Crack-filling clays and weathered cracks in the DPRI 1800 m core near the Nojima Fault, Japan: Evidence for deep surface-water circulation near an active fault

Abstract Crack-filling clays and weathered cracks were observed in the Disaster Prevention Research Institute, Kyoto University (DPRI) 1800 m cores drilled from the Nojima Fault Zone, which was activated during the 1995 Hyogo-ken Nanbu earthquake (Kobe earthquake). The crack-filling clays consist mainly of unconsolidated fine-grained materials that fill opening cracks with no shear textures. Most of the cracks observed in the DPRI 1800 m cores are yellow-brown to brown in color due to weathering. Powder X-ray diffraction analyses show that the crack-filling clays are composed mainly of clay minerals and carbonates such as siderite and calcite. Given that the top of the borehole is approximately 45 m above sea level, most of the core is far below the stable groundwater table. Hence, it is suggested that the crack-filling clays and weathered cracks in the cores taken at depths of 1800 m were formed by the flow of surface water down to the deep fractured zone of the Nojima Fault Zone during seismic faulting.     

湘潭石潭海泡石粘土矿床特征及找矿方向

赋存于茅口组下部含泥质灰岩段的矿体呈似层状、透镜状，长3500－5600m，平均厚4.39-5.15m，矿石品位一般8%-20%，最高可达65％。矿石有原岩型和粘土型两类，粘土型矿石一般呈灰－深灰色，干燥后呈灰白色，硬度1－2，比重1.6-2.3t/m^3，粘性强，可塑性好，透水性强。主要矿物成分有海泡石、石英、方解石、滑石、蒙脱石、伊利石和氟磷石等,矿石富Si、Mg、贫K、Na,CaO、Al2O3含量偏高。早二叠世江南古陆两侧局限（浅）海或海湾环境有利于海泡石沉积。在永顺－石门、安化－浏阳、怀化－浏阳成矿带，具有良好的找矿前景，估计海泡石资源量在3000万吨以上。     

黄海粘土沉积物的来源与分布

本文根据区域自然地理原理,划分黄海粘土沉积物的补给区,在粘土矿物鉴定的基础上,用法方程定量探明黄海粘土沉积物的来源与分布,绘出黄海粘土沉积物分布图。图示:黄海来源于长江的粘土沉积物的分布面积,占其总面积的56.5%,来源于黄河的占43.5%。粘土沉积物的分布同洋流、海流的分布相吻合。