Hydrothermal Dolomite in the Upper Sinian (Upper Proterozoic) Dengying Formation,East Sichuan Basin,China

Hydrothermal Dolomite （HTD） is present in the Upper Sinian （Upper Proterozoic） Dengying Formation, east Sichuan Basin, China. The strata are comprised by primary dolomite. The HTD has various textures, including zebra dolomite, subhorizontal sheet-like cavities filled by saddle dolomite and breccias cemented by saddle dolomites as well occur as a fill of veins and fractures. Also co-occur MVT type lead-zinc ores in the study area. The δ13C and δ18O isotopes of HTD in the Upper Sinian Dengying Formation are lighter than those of the host rocks, while STSr/86Sr is higher. The apparent difference in carbon, oxygen and strontium isotopes, especially the large difference in S7Sr/S6Sr isotopes ratio indicate crystallization from hot basinal and/or hydrothermal fluids. Saddle dolomite was precipitated at temperatures of 270-320℃. The diagenetic parasequences of mineral assemblage deposited in the Dengying Formation are： （1） dolomite host rock →sphalerite-galena-barite-fluorite; （2） dolomite host rock →saddle dolomite →quartz; （3） dolomite host rock →saddle dolomite→bitumen; （4） dolomite host rock →saddle dolomite →barite. The mean chemical composition of the host dolomite matrix and HTD didn＇t change much during hydrothermal process. The fluids forming the HTDs in the Dengying Formation were mixtures of freshwater from the unconformity at the top of Sinian, fluids from diagenetic compaction and hydrocarbon generation ＆ expulsion from the Lower Cambrian Niutitang Formation mudstones or the Doushantuo Formation silty mudstones, and hydrothermal fluids from the basement. The hydrocarbon reservoirs associated with the HTD were mostly controlled by the basement faults and fractures and karsting processes at the unconformity separating Sinian and Cambrian strata. The hydrocarbon storage spaces of HTD included dissolved cavities and intercrystalline pores. Dissolution cavities are extensive at the top of Dengying Formation, up to about 46m below the unconformity between Sinian an     

河南省岩土体类型及主要环境工程地质问题刍议

河南省地处中原,交通发达,人口稠密,人类工程经济活动强烈。全省地貌类型齐全,岩土体类型复杂。在水库建设、矿产开发和铁路公路建设中出现了一系列环境工程地质问题,岩土体类型不同,其工程地质特性各异,产生的环境工程地质问题亦不尽相同。分析岩土体类型及其工程地质特征,是治理环境工程地质问题、防治人为灾害的基础。本文介绍了河南省岩土体类型及其主要工程地质特征。对水库区、采矿区及交通建设中出现的环境工程地质问题进行了详细论述,为治理环境工程地质问题、防治人为灾害提供了地学依据。     

Fluid flow and mineralization of Youjiang Basin in the Yunnan-Guizhou-Guangxi area,China

Comprehensive studies, based on isotope geochemistry of C, H, O, S and Sr, chronology, common element and trace element geochemistry of fluid inclusions for the epithermal Au, As, Sb and Hg deposits in the Youjiang Basin and its peripheral areas, suggested that the ore fluid was the basin fluid with abundant metallic elements and the large-scale fluid flow of the same source in the late Yenshan stage was responsible for huge epithermal mineralization and silicification. The ore fluid flowed from the basin to the platform between the basin and the platform and migrated from the inter-platform basin to the isolated platform in the Youjiang Basin. The synsedimentary faults and paleokast surface acted respectively as main conduits for vertical and lateral fluid flow.     

Hydrocarbon Accumulation Mechanism of Sinian Reservoir in Anpingdian-Gaoshiti Structure,Middle Sichuan Basin

The Sinian reservior in Anpingdian (安平店)-Gaoshiti (高石梯) structure,Middle Sichuan (四川) basin,is of great importance to prospect for oil and gas.This article dissects the hydrocarbon accumulation mechanism of this area on the basis of comprehensive methods of organic geochemistry,fluid inclusion,modeling of hydrocarbon generation and expulsion from source rocks,and by combining structure evolutions and analyzing the key geologic features of hydrocarbon origin and trap.According to the fluid inclusion homogenization temperature analysis,there exist at least three stages of fluid charging in the Sinian reservoir.From Middle-Late Jurassic to Early Cretaceous,oil cracked to gas gradually owing to high temperature at 200-220 ℃.The Sinian gas pool was mainly formed at the stage when natural gas in trap was released from water and paleo-gas pools were being adjusted.It was a process in which natural gas dissipated,transferred,and redistributed,and which resulted in the present remnant gas pool in Anpindian-Gaositi tectonic belt.The authors resumed such an evolution process of Sinian reservoir as from paleo-oil pools to paleo-gas pools,and till today's adjusted and reconstructed gas pools.     

中新世以来滇西高原隆升的沉积学证据

印度与欧亚大陆的碰撞不仅造就了青藏高原,带动周围地区不同程度的隆起,而且通过隆升和剥蚀向高原内部盆地和环绕高原的周缘盆地提供了巨量的硅质碎屑,这些盆地的沉积记录了青藏高原隆升历史和隆升机制［１～４］。青藏高原周缘地区已成为窥视其隆升历史和机制的重要窗...     

The formation of explosive volcanos at the circum-Pacific convergent margin during the last century

Journal of Oceanology and Limnology - The circum-Pacific convergent margin is known as “the Ring of Fire”, with abundant volcano eruptions. Large eruptions are rare but very disastrous....     

Galvanic interaction between grinding media and arsenopyrite and its effect on flotation: Part I. Quantifying galvanic interaction during grinding

The Magotteaux Mill® system was used to quantify the galvanic interaction between four types of grinding media (mild steel, 15% chromium, 21% chromium, and 30% chromium media) and arsenopyrite, in situ of the mill. The galvanic current was determined from the polarization curves of individual electrodes, in situ of the mill. The high chromium media had a significantly weaker galvanic interaction with arsenopyrite, and produced a very much lower amount of oxidized iron species in the mill discharge than mild steel medium. Increasing the dissolved oxygen in the mill slurry enhanced galvanic interaction. A theoretical model was developed to describe the relationship between galvanic current and oxidized iron species in the slurry, as measured by EDTA extraction. The electrochemical data were correlated with the measurement of oxidation products after grinding under different conditions. The stronger the galvanic interaction, the higher the amount of hydrophilic oxidized iron species in the mill discharge.     

韧性剪切构造成岩成矿作用及对金矿化的控制--以内蒙古武川县后石花金矿为例

本文以内蒙古中部后石花金矿为例,简述了"韧性剪切构造成岩成矿作用"的新观点.研究表明,韧性剪切成岩过程包括细粒化作用、热流体作用、酸碱交代作用;韧性剪切带这种深层次断裂构造形成过程中,其推覆演化是逐渐减压过程,降压效应和剪切带本身的膨胀渗透作用,引起了剪切带内部积累的能量梯度(压力、温度、物质),导致弥漫于大面积围岩中和下地壳的液体进入韧性剪切带中."节流阀"作用形成韧性剪切成岩成矿热液系统.韧性剪切构造对金矿的控制核心是成岩成矿为统一的热动力系统,早期以成岩为主,中晚期以蚀变和矿化为主.