Reworking Intensity—A Key Factor Leading to the Formation of Superlarge Gold Deposits in Greenstone Belts and Metamorphosed Microclastic Rocks in China

The greenstone belt and metamorphosed microclastic rock-type superlarge gold deposits in China are hosted in metamorphic rocks and later intrusive bodies.Sedimentation.regional metamorphism and mineralization contributed a lot to the formation of the deposits,so did remelting magmatic process to some deposits,but the deposits were finally formed by reworking processes.The key factor leading to the formation of superlarge gold deposits is the reworking intensity,which for superlarge gold deposits is reflected by the large-scale reworked source rocks and even ore materials of various sources,strongly oxidized ore-forming fluids with a long and repeated active history and stable geothermal heat current.The factor which decides the reworking intensity is the network consisting of structures of different classes.     

海南乐东地区晚三叠世A型花岗岩基本特征

笔者在进行1:5万黄流市幅、千家幅区域地质调查中,首次在海南省乐东县木棉头乡一带发现晚三叠世A型花岗岩.这一发现,对研究该地区侵入岩的形成构造背景具有重要的地质意义.现将其基本特征简述如下.     

黔中--川南石炭纪铝土矿的地球化学特征

论述了黔中—川南铝土矿成矿带内早石炭世和晚石炭世铝土矿及其下伏地层的主要化学成分、稀散元素、稀土元素的地球化学特征,进而探讨了铝土矿的成矿母岩———下寒武统、下奥陶统和下志留统的泥、页岩及碳酸盐岩的成矿意义。     

破坏性矿震震前短临阶段震源过程研究

1993年5月15日19时,北京矿务局房山煤矿矿井下6号地震台附近,在4分多钟内相继发生3次破坏性矿震,最大一次震级为2.3级（M0=1.51011Nm）．利用理论地震图分析得到,这3次矿震都是以倾向滑动为主,与在场人员目击到的高倾角煤层中大量煤块倾泻而下的现象一致．主震及其震前一系列事件的6号台近场记录与普通记录不同,不仅有高频振动,而且还有低频振动．用弹性波理论和近年来一系列关于地震破裂成核理论结果进行分析表明:低频振动可能是亚临界扩展向前推进时激发的长周期波,它是不可恢复的形变;高频振动则是矿震事件,它是脆性破裂辐射的波场．根据M＝2.3事件记录及其震前5.4ｓ出现的前震记录中低频振动优势频率推测,主震发生时孕震断裂端部扩容区体积迅速增大．震前20多天直到主震发生期间,震源过程主要特点如下:亚临界扩展多次出现,在此期间孕震断裂端部扩容区体积变化不大．亚临界扩展时不仅激发产生长周期波,也常同时诱发小事件的发生,亚临界扩展优势方向与主震的滑动方向基本一致．      

Coupling between metallogenesis of the Cryogenian Datangpo-type manganese deposit in South China and major geological events

The exploration of the Cryogenian manganese deposits in the Datangpo Formation of South China has achieved great progress in recent years. It is concern in the long term there are many studies on this manganese deposits due to its particularity in the temporal and spatial distribution and the mineralization background. In this paper,we systematically summarize the previous achievements on the Datangpo-type manganese deposits. Besides,we also review current findings of Neoproterozoic global geotectonics,palaeoclimate evolution,ancient marine chemistry,and microbial evolution etc. The possible linkage between the massive metallogenesis of the Cryogenian Datangpo manganese deposits in the South China and Neoproterozoic major geological events is established. The break-up of Rodinia supercontinent led to the widespread rift basin systems in the world since the Middle Neoproterozoic. The Nanhua Basin in South China,which is a manganese-forming sedimentary basin,developed from the rift basin. The rift basin provided space for manganese deposits and controlled the distribution of manganese deposit. The hydrothermal activities at the bottom of the basin provided favorable manganese source. During the Neoproterozoic ice period(“Snowball Earth”event),global ice-sheets cut off or hindered exchanges of mass and energy between different spheres of Earth,which may lead to the widespread anoxic condition in the ice age ocean. The palaeoclimate changes during the glacial-interglacial period led to the disappearance of ice-sheets and the triggering of mass and energy exchanges between different sub-systems of Earth,followed by the variation of redox condition of the ancient sea. For the Nanhua Basin,the oxidation of surface water and the oxygen-bearing base flow provided the oxidation environment for the precipitation of manganese. Besides,new evidence indicated that manganese microbiological mineralization was the potential mechanism for manganese deposit under the microbial resuscitation condition during the interglacial period. All these major geological events have complicated connections and they provided essential metallogenic conditions for the sedimentary mineralization of “Datangpo”manganese deposit. It is believed that there is a coupling between the sedimentary metallogenesis of the Cryogenian Datangpo-type manganese deposit in South China and Neoproterozoic major geological events.     

鄯善油田裂缝特征及构造应力场

通过野外节理裂缝的观测,钻井岩心裂缝的古地磁定向与倾角测井裂缝解释,分析了鄯善油田构造应力场,得出鄯善油田储层构造裂缝发育方位主要为N30°-40°E,N30°-50°W,为一对NE、NW向共轭断裂.高角度缝和垂直缝为主.鄯善构造带是近南北挤压作用下形成的,侏罗纪末期燕山期构造运动为近SN向的主压应力模式,形成油田内一系列近SN向正断层,以及测量的NE、NW向共轭断裂.鄯善油田储层断裂是侏罗纪末期燕山期构造运动形成的.通过倾角测井椭圆井径曲线分析等方法判别的鄯善油田现今最大水平主应力方向约140°.人工压裂的裂缝方位理论上当为140°,它与320°方位的构造缝如果匹配,可能对压裂产生影响.     

砖住宅楼系列模型地震模拟试验设计--多层砖房抗震性能三向振动台试验研究之一

为保障住户地震安全和进一步研究多层砖房的抗震性能,由企业出资与研究所合作,在三向振动台上进行以四幢砖住宅为一系列的模型试验.本文为其研究论文之一,着重阐述在系列模型的设计中和地震模拟试验中的关键技术以及试验的最终结果.     

层序地层动力成因研究的周期分析方法及其应用

本文尝试时频分析技术与层序地层学原理相结合,进行陆相层序地层的周期分解,并通过与睡古构造的单成因周期对比,探讨不同级序层 层的动力成因机理。     

扬子地块西南缘晚古生代基性岩浆岩的性质与古特提斯洋的演化

扬子地块西南缘晚泥盆世至晚二叠世的基性岩浆岩具有大体类似的地球化学性质, 它们均富集Ｔｉ（ＴｉＯ２＞ ２％ ）、ＬＩＬＥ和ＬＲＥＥ（Ｌａ／Ｙｂ）Ｎ＝ ４．８～１４．６）,Ｔｉ／Ｖ（３２～６７）、Ｔｉ／Ｙ（４００～６９３）和Ｚｒ／Ｙ（３．２～７．６）比值高,具洋岛玄武岩的特征,推测它们均与地幔柱岩浆的活动有关。该地幔柱岩浆活动的时期与古特提斯洋盆演化的时期大体吻合, 但地幔柱岩浆开始喷发的中心与古特提斯初始扩张的中心相距甚远,看来,金沙江－哀牢山洋盆的张开与地幔柱岩浆活动无关。从晚泥盆世至晚二叠世,地幔柱岩浆活动的规模和强度逐渐增加,玄武岩分布中心从广西的南宁－百色之间逐渐向北西３１０°方向迁移了约６００ ｋｍ ,推测这一迁移轨迹可能受金沙江－哀牢山洋盆扩张的影响。据此估计, 金沙江－哀牢山洋盆宽度可达约１ ０００ ｋｍ 。据地幔柱岩浆轨迹与金沙江－哀牢山缝合带所夹的角度推测, 扬子地块可能经历了顺时针旋转, 与古地磁资料一致。     

用GPS复测结果计算地应变

详细地叙述了用ＧＰＳ和应变数据计算地壳水平速度和水平应变率的方法,这一方法满足变形协调性条件。用全国和大华北地区ＧＰＳ网的多期观测数据进行了试算,获得了一系列地壳水平运动和应变率场分布的图像。根据这些计算结果,可以初步得出如下结论：（１）ＧＰＳ能够有效地监测现今地壳运动和形变的信息;（２）所述的计算方法是有效的,其计算结果比直接测量结果提供了更多的有关现今地壳运动和形变的信息。