M agmatic Gold Mineralization in the Western Qinling Orogenic Belt: Geology and Metallogenesis of the Baguamiao,Liba and Xiaogouli Gold Deposits

The superlarge Baguamiao, large Liba and Xiaogouli gold deposits represent three typical gold deposits different from the Carlin type in the western Qinling Orogenic Belt. Based on Ar-Ar dating of quartz from ores, U-Pb dating of single zircon from granite, tracing of H and O isotopes and studies on the mineralogy and texture of spots and bleached alteration developed in wall rocks, this paper focuses the relations between gold deposits and granite to clarify the origin of gold deposits and the metallogenesis in the tectonic evolution of the Qinling Orogenic Belt. The comprehensive studies show that the age of the granite (148.1-244 Ma) is identical with that of the gold deposits (131.91-232.56 Ma). It is suggested that the granite has close temporal, spatial and genetic relationship with the gold deposits. The granite provides a heat source, water source and considerable amount of ore-forming material. Finally, it is concluded that the orogeny by collision, emplacement of the granite and positioning of     

广东省潮安厚婆坳锡矿床的地球化学特征

系统的地球化学研究表明:中生界上三叠—下侏罗统兰塘群系在加里东褶皱基底上发育起来的衍生含锡建造,是厚婆坳锡矿的主要物质来源。成矿流体为同生建造水,矿床形成的物理化学条件为T=260～375℃,盐度6.14～7.42%,fo_210~(-30)-10~(-37),fs_210~(-10.5)-10~(12.5),PH4.91-5.40,锡以氯的亚锡配合物形式迁移。矿床的综合地球化学异常分带序列是垂直的(上-下);Ba-Y-Mn(As.Sb.Hg)-Cu-Ni-Co-Zn-(Sn.Mo.Bi)-Pb-Ag-Ti-V-Cr-Be。     

Seismic profiles across the middle Tan-Lu fault zone in Laizhou Bay, Bohai Sea, eastern China

The stratigraphic architecture, structure and Cenozoic tectonic evolution of the Tan-Lu fault zone in Laizhou Bay, eastern China, are analyzed based on interpretations of 31 new 2D seismic lines across Laizhou Bay. Cenozoic strata in the study area are divided into two layers separated by a prominent and widespread unconformity. The upper sedimentary layer is made up of Neogene and Quaternary fluvial and marine sediments, while the lower layer consists of Paleogene lacustrine and fluvial facies. In terms of tectonics, the sediments beneath the unconformity can be divided into four main structural units: the west depression, central uplift, east depression and Ludong uplift. The two branches of the middle Tan-Lu fault zone differ in their geometry and offset: the east branch fault is a steeply dipping S-shaped strike-slip fault that cuts acoustic basement at depths greater than 8 km, whereas the west branch fault is a relatively shallow normal fault. The Tan-Lu fault zone is the key fault in the study area, having controlled its Cenozoic evolution. Based on balanced cross-sections constructed along transverse seismic line 99.8 and longitudinal seismic line 699.0, the Cenozoic evolution of the middle Tan-Lu fault zone is divided into three stages: Paleocene–Eocene transtension, Oligocene–Early Miocene transpression and Middle Miocene to present-day stable subsidence. The reasons for the contrasting tectonic features of the two branch faults and the timing of the change from transtension to transpression are discussed.     

波浪环境下多孔射流水动力特性试验

为了研究波浪对多孔射流运动和稀释过程的影响,采用粒子图像测速（PIV）及激光诱导荧光（LIF）量测系统对波浪环境下多孔射流的速度场和浓度场进行了测量。结果表明:在波浪环境下多孔射流可分为3个区域,即初始区、过渡区和混合区。在初始区,各孔射流保持各自的射流特征,相互影响较小;在过渡区,各孔射流发生分叉,并在孔与孔之间相互叠加,形成若干个汇流点,平均速度和平均浓度的峰值从射流轴线位置向汇流点处偏移;在混合区,多孔射流相互融合,其平均速度和平均浓度呈现单一的“坦峰”分布,形式上表现为单孔射流的水动力特征。通过对比分析发现,波高和周期的增大以及射流初始速度的减小可使汇流点的位置向下偏移,多孔射流将更快地进入过渡区和混合区。     

Iron loss of paddy soil in China and its environmental implications

Science China Earth Sciences - Iron (Fe) is an important element for the terrestrial and marine ecosystems through its biogeochemical cycling on the Earth’s surface. China has a long rice...     

金矿化过程中两个地球化学问题探讨

论述了金矿化过程中的两个地球化学问题,即沉积喷流作用与金矿化的关系,金与铅锌矿化的关系,海底沉积喷流作用不仅能形成重要的贱金属硫化物矿床,而且也导致金的明显富集;大量的地球化学研究工作已识别出一些沉积喷流型金矿床,揭示出部分太古宙绿岩石带中的脉状金矿床与沉积喷流作用密切的时空关系。     

Li同位素组成对太古宙海水相关的表生环境过程的初步限定

研究试图利用Li同位素地球化学对太古代海水相关的表生环境过程进行初步的限定.通过对来自南非Kaapvaal克拉通的海相碳酸盐岩样品进行Li同位素分析,发现在3.0～2.9 Ga期间形成的碳酸盐岩δ7Li值为～+1‰,而在2.6～2.5 Ga期间,碳酸盐岩δ⁷Li值达到7‰～10‰.经过反演计算得到对应时代的海水Li同位素组成分别为～+12‰和～+20‰,均明显低于现代海水值(～+31‰),但是2.6～2.5 Ga期间的海水δ7Li值要比3.0～2.9 Ga时高出8‰.作为大陆硅酸岩风化的有效示踪剂,太古代海水较低的Li同位素组成表明当时的地表风化以源岩溶解为主,次生矿物形成极少,在3.0～2.5 Ga期间,海水整体温度下降以及次生矿物形成增加可能共同导致了海水δ7Li值的升高.通过对太古代碳酸盐岩的Li同位素研究能够有效反演古海水的Li同位素组成,并为了解太古代表生风化过程对海水的影响提供了新的信息.     

沉积（火山）岩中铅锌矿化与金矿化的关系——兼论我国铅锌矿化集中区的金矿勘查

近年来,我国在铅锌矿区或外围发现了越来越多不同类型的金矿床,铅锌矿化与金矿化之间的相互关系及其勘查指示意义已引起了广泛的关注。沉积（火山）岩中的铅锌矿化基本可分三种类型,不同类型的铅锌矿化有不同的成矿环境,而金的成矿地质事件是在特定地区与特定的热—构造事件相互耦合的。研究发现,只有在经历了后期强烈的热—构造事件的Sedex型或VMS型铅锌矿区才具备形成金矿化的条件,是金矿勘查的有利地区;MVT型和后期缺乏热—构造事件的Sedex型或VMS型铅锌矿区不具备形成金矿化的条件,是金矿勘查的不利地区。     

西昆仑海相火山岩及其有关大型铜矿成矿前景的初步分析

新疆西昆仑地区铜矿化因其较广泛的时空分布特点而为人们所重视。其中尤以海相火山岩型铜矿找矿前景备受关注。海相火山岩主要分布于昆盖山地区和库地地区,二者火山岩规模、岩石组合、地球化学特点以及活动时代均有较大差异。昆盖山地区火山岩具有双峰式火山岩的特点,玄武岩（或细碧岩）属于碱性系列或钙碱性系列,有较强的分异,代表了大陆边缘裂谷活动的产物,但裂谷的规模可能不是很大。库地火山岩属于一个完整的蛇绿岩套的一部分,均为拉斑玄武岩,分馏分异弱,与典型的NMORB相似,代表了古洋壳残余,该地区可能存在较大规模的海盆。对海相火山岩及其铜矿的研究表明,无论是昆盖山地区还是库地地区,主攻铜矿类型是与基性火山岩有关的块状硫化物型即塞浦路斯型,但大型以上规模的富铜矿找矿前景不明朗,找矿难度较大。