The Paleoproterozoic Supracrustal Kolhan Group in Singhbhum Craton, India and the Indo-African Supercontinent

The 2.0 Ga supracrustal Kolhan Group to the south of Chaibasa in Singhbhum Craton, eastern India is a shale-dominated succession deposited in continental rift setting. It begins with thin plane- and cross-bedded red and purple sandstones consisting of ferric oxide-rich quartz arenite with beds/lenses of conglomerates deposited in shallow, ephemeral braided streams. The thick and extensive shale deposited in lacustrine environment overlies the sandstone. The shale succession consisting of thin and even bedded shale and silty shale contains lenticular bodies of finely laminated thin-bedded limestones and manganese-rich interval towards the basal part. It lacks subaerial exposure and tidal features and at places exhibits small wave ripples on bed surfaces.

Petrography, geochemistry and CIA values of Kolhan siliciclastics, suggest passive margin tectonic setting, an intensely weathered low-relief provenance dominantly composed of granitoid rocks and a warm and humid palaeoclimate. Based on similarities in age, lithology, petrography, depositional environment and type of mineralization, the Kolhan Group in Singhbhum Craton is correlated with manganese bearing Wyllies Poort Formation of the Soutpansberg Group, northeast Kaapvaal Craton, South Africa. This correlation suggests the two cratonic blocks may formerly have been juxtaposed and represents the sundered fragments of an Archean Craton.     

Petrography,provenance, diaganesis and depositional environment of Murree Formation in Jhelum Valley,Sub Himalayas,Azad Jammu and Kashmir,Pakistan

The clastic sediments of the Murree Formation of Miocene age are exposed in Jhelum valley areas of Azad Jammu and Kashmir Pakistan. Field observations revealed the cyclic deposition in the Murree Formation. The sandstone, siltstone, and shale constitute a single cycle within the formation. This single unit is divided into five different lithofacies which constitute the Bouma sequence in the Murree Formation. The Murree Formation shows faulted contacts with Panjal Formation and Nagri Formation in the study area. The modal mineralogy data obtained from the petrography of sandstone indicates that sandstone is litharenite and lithic greywacke. The mineralogical and textural data suggests that sandstone is compositionally mature and poorly to moderately sorted. The dominantly angular to sub angular quartz grains show nearness of the source area. Fractured and sutured quartz grain reveals tectonodiagentic changes that occurred in Murree Formation. The sandstone experienced diagenetic changes. The pressure solution and cementation reduced the primary porosity of sandstone. However, alteration of feldspar and fractures in grains have produced secondary porosity. The X-ray diffraction (XRD) of the shale samples indicates that shale of the Murree Formation is argillaceous and dominated by illite clay mineral. The illite crystallinity values indicate very low grade metamorphism of Murree Formation in core of Hazara Kashmir Syntaxis. The petrographic data suggests that the provenance of sandstone is recycled orogen. Quartz is of igneous and metamorphic origin. Feldspar (albite and microcline) composition suggests its derivation from acidic igneous rocks. The rock fragments of volcanics, slate, phyllite, and schist suggest igneous and metamorphic provenance. The petrographic data suggests that at the time of deposition of Murree Formation, igneous and low grade metamorphic rocks were exposed. However, presence of some clasts of carbonates indicates that sedimentary rocks were also exposed in the source region. The quartz content and clay minerals in the shale revealed that source region was igneous and metamorphic rocks. Cyclic deposition, lithofacies, and various sedimentary structures like cross bedding, ripple marks, and calcite concretions suggest that deposition of Murree Formation occurred in fluviatile environment by meandering river system having decreasing turbidity current.     

西藏北部班戈地层分区下白垩统郎山组、康曲组和余穷组地层层序研究

在西藏自治区北部区域地质调查过程中 ,在班戈地层分区的下白垩统郎山组之上发现一套厚约 180 0 m的滨海—浅海相碳酸盐岩、陆源细碎屑岩岩石组合 ,该套组合不属于郎山组定义之内 ,且出露良好、层序稳定、标志清楚、厚度巨大、化石丰富 ,并具有很强的可填图性。因此 ,我们将整合于郎山组之上 ,岩性以杂色微—薄层状钙质泥岩、钙质 (粉 )砂岩与泥质生物灰岩的韵律产出为特征 ,产圆笠虫、腹足类、双壳类等化石的地层命名为康曲组 ;将整合于康曲组之上 ,下部以灰—深灰色中薄层状泥质生物灰岩、圆笠虫泥晶灰岩、钙质泥岩等韵律出现为特征 ,上部以灰色中—厚层状含硅质结核圆笠虫泥晶灰岩、圆笠虫泥晶灰岩夹灰绿色薄层状钙质砂岩为特征 ,富含圆笠虫、腕足类、腹足类、双壳类及海胆等化石的地层定名为余穷组。时代均置于早白垩世晚期     

滇西海相侏罗系

前言我国的海相侏罗系有两种类型。一种是特提斯(Tethys)型,属于这一类型的有西藏、青海南部、新疆、滇西等地区的海相侏罗系,这些地层的岩性和动物群性质或多或少都能与欧洲、印度西部、东非甚至东印度群岛的侏罗系相对比。另一种是环太平洋型,属于这一类型的包括湖南、广东、东北等地区的海相侏罗系。除东北拉丹哈达岭有侏罗纪的海相沉积外,其余地区仅含有海相里阿斯统的中下部。关于在中国以及中南半岛地区特提斯型与环太平洋型两种里阿斯时期海相地层的关系,至今仍然不清楚。滇西是我国海相中生代地层发育比较好的地区之一,过去虽然经过洛齐(L.vonLoczy,1893年)和布朗(Brown,Coggin J.,1916年)等人的调查,但对中生代地层,尤其是侏罗系缺乏详细研究。     

广东紫金铁嶂锡矿床地质特征及矿床成因探讨

铁嶂锡矿床赋矿围岩为下侏罗统金鸡组下部的砂页岩,其锡含量较高,为矿源层。矿体分布于北东向和北西向断裂构造中,可分为大脉型与细脉带型矿体。锡石有两类:一类为沉积的胶状锡石和由胶体变晶生成的微晶锡石,分布于富动植物化石和碳质的千枚状页岩和富锡的砂岩结核中;第二类为粒状锡石,与石英、硫化物一起呈脉状产出。矿床系沉积变质热液改造成因。     

泰国难府-程逸缝合带中灰岩块的 虫筳 类生物地层学

The study area, Nan Province, northern Thailand is geotectonically situated within the Nan-Uttaradit Suture, the once back-arc basin between the Sukhothai Zone and Indochina Block. Permian Fusulinacean fauna from limestone blocks within the suture has been investigated and the Nan area has been mapped in detail. These may provide the useful information for understanding the faunal assemblage and overall ge-ometry of stratigraphic successions in the basin. The strata were intensely folded and thrust. Scattered Per-mian limestones found in Nan area are blocks within shale interbedded with tuffaceous rock. The contact between this unit and the adjacent units, the strongly foliated shale and tuffaceous sedimentary strata that are mildly metamorphosed and giving phyllitic tex-tures, has been interpreted as a west-dipping normal fault, namely the Pha Sing Fault. This fault runs par-allel to the Highway no.1080 (Nan-Tha Wang Pha). Middle and early Late Permian fusulinacean fauna found in the Nan area contains Neoschwagerina, Pseudodoliolina, Colania, Lepidolina, and Colaniella. Additionally, late Early Permian fusulinacean and Middle Triassic radiolarian fauna have been reported in this area (e.g., Fontaine, 2002; Saesaengseerung et al. 2008). These paleontological data show the existence of Nan Back-arc Basin during late Early Permian (Artin-skian) to Middle Triassic. Moreover, the similarity of fusulinacean assemblage yielding Permian limestone blocks of the Nan Back-arc Basin and the ones of the Indochina Block has been interpreted that the Permian limestone blocks in the Nan Back-arc Basin were part of the continental shelf within the Indochina Block.     

四川盆地下侏罗统陆相页岩气源储特征及耦合评价

四川盆地陆相页岩气勘探前景良好,目前已在川东北地区下侏罗统获得良好页岩气显示和工业气流.与海相页岩相比,陆相页岩具有相变快、岩相组合类型多(夹层发育)、有机质丰度低和源储配置关系复杂等特点.运用"源储耦合"研究思路,利用宏观-微观结合的储层表征技术对下侏罗统自流井组大安寨段页岩的烃源特征、储集特征及其耦合关系开展了分析...     

塔中Ⅲ区碳酸盐岩储层去泥质反演及泥质充填判别

塔里木盆地塔中Ⅲ区奥陶系碳酸盐岩储层是近年来勘探重点区域,良里塔格组储层内沉积泥质灰岩条带,以及一间房组洞穴顶部存在的沉积泥质条带,给储层预测带来了较大难度。为提高储层预测精度,分析奥陶系良里塔格组和一间房组储层内泥质展布规律,建立沉积泥质灰岩条带背景纵波阻抗体,完成了无井约束叠后地质统计学反演。研究结果表明,无井反演储层预测纵向发育位置、储层级别和已钻井吻合较好。利用叠前同时反演得到纵横波速比,通过纵波阻抗与纵横波速比交会图分析法,划分了一间房组优质储层、泥质充填储层、基质灰岩分布区间,对洞穴型储层泥质充填、叠前流体预测反演进行探索,确保储层预测的可靠性。     

济阳坳陷沾化凹陷罗家地区古近系沙河街组页岩储集特征分析*

利用岩石薄片和扫描电镜分析等测试技术, 可以将济阳坳陷罗家地区古近系沙河街组页岩段储集空间分为孔隙和裂缝两大类。孔隙又可以分为黏土矿物晶间孔、碳酸盐矿物晶间孔、黄铁矿晶间微孔、碎屑颗粒溶孔和砂质粒间微孔5个亚类;裂缝分为成岩裂缝和构造裂缝两大类, 成岩裂缝又可以分为层间裂缝和粒缘裂缝两类。裂缝与基质孔隙之间, 存在一个微米尺度的重合带, 反映了储集空间发育继承性的特点, 油气聚集在以层间裂缝为中心, 粒缘裂缝等次级裂缝和较大的碳酸盐晶间孔为骨架, 以各类晶间孔隙、黏土微孔和溶蚀孔隙为基质的储集空间网络中。储集空间发育与岩性关系密切, 纹层状泥质灰岩物性较好, 相应的页岩物性具有基质渗透率极低和裂缝导流能力较强的特点。     

陕西韩城寒武纪三叶虫生物地层

陕西韩城寒武系出露良好 ,化石丰富 ,假整合覆盖于厚约 2 0 m的霍山组石英砂岩之上 ,从下寒武统上部至奥陶系为沉积连续。本区寒武系主要以紫色和黄色泥页岩、泥灰岩、灰岩和白云质灰岩为主 ,从下到上可划分为馒头组、毛庄组、徐庄组、张夏组和三山子组。根据在本区寒武系发现的三叶虫化石 ,韩城地区寒武系可划分为 14个生物带 ,自上而下为 :Blackwelderia带 ,Damesella带 ,L iopeishania带 ,Dorpyge richthofeni带 ,Crepicephalina带 ,Manchuriella带 ,Poriagraulos带 ,Inouyops带 ,Sunaspis带 ,H suchuagia带 ,Shantungaspis带 ,Probowmaniella带 ,Weijiaspis带和 Redlichia murakamii带。     

广西古袍金矿区花岗斑岩侵入期后多期热液成矿作用的Ar-Ar年龄证据

古袍矿区的花岗斑岩出露于古袍复向斜西部扬起部位。围岩地层主要为寒武系水口群浅变质砂岩、粉砂岩、硅质岩及板岩、千脉岩和破质页岩。花岗斑岩和花岗斑岩内的石英脉体中石英样品的40Ar/39Ar年龄数据表明户，40Ar/39Ar坪年龄值在187.87±1.53 Ma至244.88±2.48 Ma之间，是加里东期花岗斑岩成岩作用之后，海西、印支或者燕山早期多期构造热液作用的产物。金矿化与花岗斑岩成岩后的多期次构造热液作用有关。主要受控于断层破碎带及其中充填的石英脉和黄铁矿化。     

浙江江山城建区地质条件分析与评价

详细研究了浙江江山城建区的地层、岩性和构造，分析了这些基础地质条件对城市建设的影响。城建区地层复杂，出露了晚元古代以来13个组的地层，还有侵入岩和火山碎屑岩出露。地质体中的层理、接触面以及软弱夹层对地质体的结构强度有很大的影响。城建区内碳酸盐岩分布最广，有岩溶塌陷现象，对城市建设不利。侵入岩、火山碎屑岩和砂岩，坚硬致密，风化裂隙不发育，是很好的建筑基岩。志棠组含砾粗砂岩、硅质岩岩性虽然较坚硬，但多被断裂破碎，对城市建设有一定的影响。页岩、泥岩和粉砂质页岩属软质岩石，易变形。城建区断裂构造发育，对城建区的工程建设有很大的影响，但区内无新的构造活动，无大于4．5级地震的历史记录，地震烈度为Ⅵ度，城建区所在的区域地壳稳定。根据基岩、土层和断裂构造的性质和特点，笔者把城建区划为三个级别：一级区，适宜重大工程的建设；二级区，进行高层建筑时要预先实施岩溶地基处理；三级区，工程条件差，应避开建设重大工程。     

贵州三都丰乐铁矿床地质特征及成因初探

贵州省三都县丰乐铁矿位于都匀以南,矿体呈层状、似层状产状,含矿岩系产于泥盆系大河口组,岩性为铁质砂岩、含铁砂岩、泥质砂岩等,脉石矿物主要为石英、白云石等,矿石品位较低,属贫铁酸性铁矿石。认为其属于＂宁乡式＂铁矿床,赤铁矿鲕粒以胶体化学方式沉积,成因类型系同生沉积成因。     

页岩油的储层特征及其影响因素分析——以沾化凹陷罗家地区为例

为查明沾化凹陷罗家地区古近系沙河街组三段下亚段页岩油的储层特征及其影响要素,通过岩心、薄片、扫描电镜等多种资料综合分析,开展页岩油储层岩性、储层空间类型、影响因素及页岩油储层评价参数的研究。结果表明: 综合矿物成分和沉积构造2个因素,可将研究区页岩油储层岩性划分为7种类型; 不同岩性储集空间发育有较大差异,纹层状泥质灰岩和纹层状灰岩储集空间最为发育,纹层状灰质泥岩储集空间较发育,块状泥岩储集空间发育一般,块状泥质灰岩、块状灰质泥岩及纹层状粉砂岩储集空间发育较差; 研究区页岩油储层储集空间的发育主要受矿物成分、沉积构造、有机质含量和赋存方式以及成岩作用的影响。以此为基础,选取方解石含量、纹层状构造、总有机碳(Total Organic Carbon,TOC)含量、镜质体反射率(R_o)及孔隙度作为页岩油储层评价参数,将沾化凹陷罗家地区页岩油储层分为优质储层、有利储层和不利储层3类。     

巴西坎普斯盆地油气地质特征

坎普斯盆地为典型的被动大陆边缘拉伸裂谷盆地,由前裂谷期(非海相)、同裂谷期(过渡相)及后裂谷期(海相)三个构造层组成.含盐层序为区域盖层,盐下层序泥页岩和盐上层序坎普斯组泥页岩为局部盖层;主要烃源岩为下白垩统拉高亚费耶组湖相黑色钙质页岩;古近系和新近系浊积砂岩为主力储集体,上白垩统浊积岩也是重要储层,下白垩统尼欧克姆阶...     

Characteristics and influencing factors of shale oil reservoir: A case study of Luojia area in Zhanhua sag

In order to find out the characteristics and influencing factors of shale oil reservoir in the lower third member of Shahejie Formation of Paleogene in Luojia area of Zhanhua sag, the authors studied the lithology, space type, influencing factors and evaluation parameters of shale oil reservoir by comprehensive analysis of cores, thin sections, SEM and so on. The results show that mineral composition and sedimentary structure are two important factors, based on which the shale oil reservoir can be divided into seven types. The reservoir space of different lithological types varies greatly. Laminated argillaceous limestone and limestone reservoirs were mostly developed, and laminated gray mudstone reservoirs were relatively developed, followed by massive mudstone. The massive argillaceous limestone, massive grey mudstone and laminated siltstone reservoirs were less developed. The reservoir space of shale oil reservoir in the study area was mainly influenced by mineral composition, sedimentary structure, organic matter content and occurrence mode as well as diagenesis. On this basis, calcite content, laminar structure, TOC content, R_o and porosity were selected as evaluation parameters and the shale reservoir in Luojia area of Zhanhua sag was classified into three types: high quality reservoir, favorable reservoir and unfavorable reservoir.     

Argillite debris converted to bauxite during karst weathering: evidence from immobile element geochemistry at the Olmedo Deposit, Sardinia

The Olmedo bauxite deposit occurs in the Nurra district of northwest Sardinia. It forms a stratiform horizon in Cretaceous limestone and marl. Uplift in mid-Cretaceous had exposed recently deposited limestone to karst weathering, and a layer of argillaceous debris accumulated on its surface and was partly converted to bauxite. Intermediate products were desiccated marl, bauxitic argillite and argillaceous bauxite. Subsidence followed, and the bauxite was preserved by the deposition of late Cretaceous limestone and other sediments. Uplift in Oligocene-Miocene time, with ensuing erosion, exposed the bauxite horizon to its present configuration. Concentrations of normative minerals illustrate chemical processes and the build-up of Al in the bauxite horizon. Plots of chemical data and correlation coefficients show that Al, Ti, Zr, Nb, Th, Cr and V were immobile during the bauxitization process. Mass changes point to large net removal of Si, Mg and K from the system, although some of this material and slightly mobile Al were reprecipitated in the underlying argillite and altered marl. Immobile element ratios trace the source of the bauxite to the underlying argillaceous limestone. Al in the bauxite was accumulated from the degradation of 25 to 50 m of the argillaceous limestone. Received: 10 June 1996 / Accepted: 15 April 1997     

贺兰山中南段米钵山组沉积特征及其物源分析

贺兰山中南段米钵山组地层岩性主要为钙质角砾岩、砾岩、互层状的砂岩或含砾砂岩以及页岩、含砾页岩、颗粒灰岩等,是一套区域浅变质、厚度巨大、具不同程度变形和深水陆源浊积岩组合的斜坡沉积,发育有复理石韵律层理及典型的浊积岩鲍马序列。研究表明中奥陶统米钵山组沉积期是贺兰“冷”裂谷活跃的时期,该时期的沉积特征对探讨贺兰山早古生代的构造格局及岩相古地理方面尤为重要。对米钵山组的地球化学分析结果表明,稀土元素La、Ce、∑REE、δEu等特征值与大陆岛孤和活动大陆边缘构造环境相似。综合该组沉积的矿物特征、构造环境及区域背景,其物源应来源于其南部的祁连造山带及邻区阿拉善地块,具有二元物源供给的近源沉积特征。     

The Early Proterozoic Nabberu Basin and associated iron formations of Western Australia

Rocks of the Early Proterozoic Nabberu Supergroup were deposited in the Nabberu Basin along the northern margin of the Archaean Yilgarn Shield in Western Australia. The Nabberu Basin consists of three tectonic-sedimentary units known as the Earaheedy, Glengarry and Padbury Sub-basins.The Earaheedy Group within the easternmost sub-basin is divided into a lower Tooloo Sub-group and an upper Miningarra Sub-group, representing succeeding sedimentary cycles totalling some 6000 m of shallow water sediments. The Tooloo Sub-group comprises thin quartzose to arkosic clastics (Yelma Formation) which rest unconformably on Archaean rocks, and are overlain by chert, shale, iron formations and minor carbonate (Frere Formation), and thinly bedded carbonate, shale and sandstone (Windidda Formation). The overlying Miningarra Sub-group includes sandstone and shale (Wandiwarra Formation), super-mature quartz sandstone and arkosic siltstone (Princess Ranges Quartzite), fine arkosic sandstone, siltstone, shale and carbonate (Wongawol Formation), limestone, shale and sandstone (Kulele Creek Limestone) and sandstone and shale (Mulgarra Sandstone). Distinctive stromatolite assemblages occur in carbonate units throughout the sequence.Iron formations of the Frere Formation are similar to those of the Lake Superior and Labrador Provinces of North America, and commonly have a distinctive pelletal (intraclastic) texture, but are locally oolitic or laminated. Benthonic microfossils found at one locality are identical to those in the Lake Superior iron formations (Walter et al., 1976).West into the Glengarry Sub-basin and Peak Hill—Robinson Ranges area the basal clastics become considerably thicker, finer-grained and more varied, and are commonly interbedded with basaltic volcanics and greywackes. The Peak Hill Beds (MacLeod, 1970), Finlayson Sandstone and Maraloou Formation (Bunting et al., 1977) may be lateral equivalents of the Yelma Formation, while the overlying Horseshoe Range Beds, Labouchere Formation and Robinson Range Formation (Barnett, 1975) are possible equivalents of the Frere Formation. The Millidie Creek Formation may be equivalent to the Wandiwarra Formation.Deformation of the Nabberu Basin has resulted in the development of the Stanley Fold Belt in the north and the Kingston Platform in the south. On the Kingston Platform the rocks dip very gently north, but deformation increases northwards. A slaty cleavage becomes more conspicuous in this direction, while folds become tighter, overturned southwards and cut by north-dipping thrusts. The fold belt trends west-northwest across the eastern portion of the basin before swinging to the southwest. Archaean basement is increasingly involved in the deformation and becomes progressively more gneissic as the Early Proterozoic rocks become more strongly schistose. Refolding of early structures is pronounced in the west. Metamorphic grade, based on mineral assemblages in basic, pelitic and carbonate rocks and iron formations, also increases north and northwest, reaching a maximum grade of granulite facies west of the Robinson Ranges. The sediments are essentially unmetamorphosed in the southeastern part of the basin.     

东昆仑南缘西大滩混杂堆积

<正> 西大滩混杂堆积,出露于东昆仑中段南缘,青藏公路的西大滩南侧之煤矿沟(图1)。秦德余、李光岑1976年首次认为是混杂岩,但未做描述。青海区调一队四分队在填图时也注意了这一现象。笔者根据他们提供的线索,对该混杂堆积进行了观察和描述。 根据野外收集的实际资料,笔者认为西大滩混杂堆积是滑塌混杂堆积,它向东、西延伸而为混杂堆积带,依混杂岩块的岩性种类及空间分布关系,由南到北可划分三个混杂堆积层,三层在成因上互有联系。