准噶尔盆地基底的探讨：来自原泥盆纪卡拉麦里组砂岩碎屑锆石的证据

准噶尔盆地基底的属性和时代,长期以来一直是地质界激烈争论的问题。根据区域地质背景分析,准噶尔盆地东北缘卡拉麦里蛇绿岩带南侧出露的一套基本连续的、被置于中志留统-下石炭统的浅海相陆源碎屑沉积岩系的物源区,位于准噶尔盆地东部盆地堆积物之下。为此选择其中被1:20万区调置于中泥盆世卡拉麦里组上部层位的砂岩进行碎屑锆石SHRIMP U-Pb 定年研究,以期获得准噶尔盆地东部基底时代和属性的信息。测定的86颗碎屑锆石、89个点的年龄分布范围从(327±8)Ma 至(3073±10)Ma;其中碎屑锆石的表面年龄主要集中分布在320Ma～540Ma,显示出多峰的特征,其主峰为 365Ma,次要的峰分别为460～480Ma、510～520Ma 和530～540Ma。该样品中还含有至少22粒表面年龄大于550Ma 的碎屑锆石,其中550～690Ma 的碎屑锆石有4粒,827Ma～1083Ma 的碎屑锆石有8粒,1513Ma 和1700Ma 锆石各1粒,1942Ma～2051Ma 的锆石有2粒,2464～2490Ma 和2876Ma～3073Ma 的碎屑锆石各3粒。根据样品的岩石学特征和碎屑锆石的矿物学特征及表面年龄,结合区域岩浆活动的分析,我们获得如下初步结论:(1)所研究砂岩的沉积时代不是泥盆纪的,可能是早石炭世晚期,其源区位于准噶尔盆地东部;(2)源区地质体组成主体是奥陶纪至石炭纪活动陆缘岩浆岩,寒武纪至新元古代中期和新元古代早期至中元古代等时期的岩浆杂岩等组成,以及推测的少量早前寒武纪杂岩;表明准噶尔盆地东部的基底为奠基在前奥陶纪陆壳基底之上的古生代岛弧。     

塔里木盆地中部泥盆系东河砂岩成岩序列与储集性能控制因素?

根据对岩石铸体薄片和阴极发光薄片、地层厚度、古地温梯度以及镜质体反射率等资料分析研究认为：塔中地区东河砂岩经历了压实作用、粘土胶结、石英次生加大、碳酸盐胶结、溶蚀作用、自生高岭石沉淀等多种成岩作用，目前已经达到了晚期成岩阶段。这些成岩作用在塔中4井以东和以西的地区存在较明显的差异，西部进入早成岩阶段B期和晚成岩阶段A期的时间较早，成岩演化程度较高，且具有下部溶蚀上部胶结的分带性；而东部则反之。优质储层主要分布于颗粒成分较纯、泥质含量较低、构造位置上长期处于高部位、被油气充注，但未被晚期碳酸盐胶结的地区。即二叠纪以来长期处于构造高部位的前滨-临滨相带内。     

Fluvial architecture and diagenesis of the Mt Eclipse Sandstone,northern Ngalia Basin,Australia

The Upper Devonian to Carboniferous Mt Eclipse Sandstone is a basin-wide host to uranium mineralisation in the Ngalia Basin, NT. The fluvial depositional architecture and diagenesis of the Mt Eclipse Sandstone at the Bigrlyi uranium deposit on the northern margin of the basin are deduced from hyperspectral mineral results captured from 200 drill holes, combined with core and outcrop observations across a ~10 km strike length. The succession hosting the uranium mineralisation is interpreted to be deposited in the lower parts of a mature alluvial fan system with low slope angle and dominated by immature, kaolinised, medium-grained subarkosic sandstones and patchy calcite cement. This study reveals the fluvial channel sequence is estimated to be 3 km wide, 100–200 m thick and sourced from the north. This multidisciplinary study also uncovers the complex interaction and codependencies between fluvial/groundwater activity, evaporation, oxidation, fluctuating pH and detrital mineralogy controlling early diagenetic processes in the alluvial fan sediments. Carbon isotope data identify calcite cements as groundwater calcrete, while strontium isotope data suggest limited prolonged water–rock interaction prior and during calcite cementation. The petrographic data reveal the importance of early calcite cement occluding all pore space and preserving detrital minerals from later diagenetic processes. The hyperspectral results highlight the intermittent distribution of the calcite cement and the commonly repetitive mineralogical zonation throughout the 200 drill holes, including the inverse spatial correlation between kaolinite ± goethite ± gypsum vs white mica ± hematite dominated zones. X-ray diffraction and the hyperspectral data reveal the scarcity of early diagenetic clay minerals such as montmorillonite. This paper is the first to report on a systematic mineralogical and sedimentological study for the Mt Eclipse Sandstone. By focusing on the diagenesis and fluvial architecture of this stratigraphic unit, a framework to support exploration for sediment-hosted uranium deposits is established.     

云南凹地苴铜矿多阶段脱水成矿模式

凹地苴铜矿矿物在剖面上具从辉铜矿－斑铜矿－黄铜矿－黄铁矿分带现象,几个分带相互叠加,矿床形成了于氧化还原界面附近,种种证据表明含矿溶液因多阶段脱水形成,矿床是通过双层卤水在氧化还原界面附近相互反应成矿。     

可地浸砂岩型铀矿盲矿识别模式

伊犁盆地南缘是典型的可地浸层间氧化带砂岩型铀矿产出区,近年来诸多单位对其控矿因素、成矿环境与成矿远景进行了研究。由于此类型矿床产出部位地表覆盖严重、多属盲矿,因此对其识别定位既是找矿工作中的技术关键,亦是难点。受核工业北京地质研究院开放实验室资助,笔者以伊犁盆地南缘为研究对象,对可地浸层间氧化带型砂岩铀矿盲矿的识别模式进行了专项研究。     

CO2矿物捕获能力的研究进展

全球碳存储的研究表明, CO2最稳定的存储方式是 CO2的矿物捕获, 即将 CO2注入到地下,使其以方解石、菱铁矿、白云石及片钠铝石等碳酸盐矿物的形式存在.适合 CO2矿物捕获的岩石类型主要有火山岩、砂岩和火山碎屑岩.分析了3种岩石类型的金属元素含量、金属元素的释放能力、与 CO2反应生成的矿物类型及对 CO2的捕获量,并比较了3种岩石类型对 CO2矿物捕获能力的差异.其中玄武岩等火山岩的金属离子含量高,但其孔隙空间有限,制约了成岩反应,且 CO2注入后具有逸散的风险;砂岩分布广泛,有足够的孔隙利于流体注入,但是金属离子含量相对较低,对 CO2的矿物捕获所需时间相对较长;火山碎屑岩则结合了前2种岩石类型在矿物捕获方面的优势,是一种理想的 CO2矿物捕获的岩石类型.     

Brackish water faunas from the St Maughans Formation: The Old Red Sandstone section at Ammons Hill,Hereford and Worcester,UK, re-examined

The disused railway cutting at Ammons Hill, Hereford and Worcester, exposes a sequence of beds belonging to the Devonian St Maughans Formation of Lochkovian (Gedinnian) age. The beds are of Old Red Sandstone facies, but contain brackish water faunas. These faunas occur at a level generally considered to be above the level of marine influence that affected the older Raglan Mudstone Formation of mainly Přídolí Series age. The section, described by King in 1934, is now overgrown, but was excavated in 1986 by the British Geological Survey during its survey of the Worcester 1:50000 sheet. The evidence of the section calls for slight amendment of Allen's (1985) model of an interrupted transition from marine deposition in Ludlow time to freshwater deposition in Gedinnian time that was complete by the time of the formation of a regionally extensive calcrete palaeosol, the Psammosteus Limestone. Subsequent transgressive events took place before the establishment of apparently wholly fluvial and floodplain environments.     

A tunnel section through a prograding Namurian (Arnsbergian,E2a) delta,in the western Bowland fells,north Lancashire

The Wyresdale Tunnel was driven through Roeburndale Grit Group sediments in the western Bowland Fells. An Arnsbergian age for the strata is confirmed in a palynological study. The tunnel provided a section through a prograding delta front sequence, and proved the Roeburndale Grit Group to be much thicker than previously recorded. Syndepositional instability within the deltaic sediments is illustrated by slumps and debris slides. A comparison is made with modern deltas. It is suggested that the regional variation in sediment thickness is tectonically controlled.     

Palynofloras from tournaisian lacustrine and tidal sequences in slieve bloom,counties laois and offaly,Ireland

Tournaisian miospore assemblages are used to determine the age of some plant-bearing horizons in the Old Red Sandstone succession of the Slieve Bloom Mountains, Counties Laois and Offaly, Ireland, and the sedimentology and conditions of deposition of the productive lithologies are described. The age of the marine transgression which terminated continental sedimentation is indicated, and the associated depositional environment is discussed. Comparisons are made with other micro- and macrofloras from Ireland, Britain, Canada, the U.S.S.R. and Bear Island.     

砂岩铀矿床新构造渗出成矿作用

砂岩铀矿床，特别是产于油气盆地中的砂岩铀矿床是铀矿床的重要类型。油气盆地的完整的补-径-排水动力系统是砂岩铀矿形成的基本动力学条件，但这种"补"是通过盆缘山体蚀源区"补"还是通过盆地深部流体"补"，这种"径"是沿着砂岩层由高处往低处径流还是由低处向高处径流，以及成矿后的流体是如何排出的，都没有充分的论据进行过论述。砂岩型铀矿成矿物质来源、运移和沉淀富集机理仍是有待解剖研究的重大理论课题，为此，笔者换了个视角，从盆地深部烃源岩提供成矿物质来源的思路，重新思考砂岩铀矿的沉淀富集机理。研究认为，砂岩铀矿床是新构造期渗出成矿作用下的产物，铀及伴生元素来源于盆地深部烃源岩（内源或深源），而不是来源于现代蚀源区（外源或浅源）；铀的迁移是在新构造期切层断层发育并成为导矿构造的前提下，在强还原环境中以有机络合物形式存在的铀等金属元素，由深部向浅部迁移，而不是在氧化带中以碳酸铀酰络合物形式由浅部向深部渗移；铀等元素的沉淀是由于氧化还原作用而发生的，具体说是先氧化后还原而形成的，而不是直接由还原作用形成的。最后建立了油气盆地砂岩铀矿床新构造渗出成矿模式。