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1.
内容提要:布青山地区马尔争组复理石岩系位于东昆仑南缘,其主体是一套沉积于深海—半深海环境的浊积岩,本文研究了复理石岩系中砂岩的沉积岩石学、碎屑骨架模型及岩石地球化学特征。碎屑组分统计结果表明其砂岩类型主要为长石岩屑砂岩,石英、岩屑、长石的平均含量分别为42%、37%、21%,物源类型为切割型岛弧及再旋回造山带。马尔争组砂岩w(SiO2)含量介于50.18%~74.05%,平均值为66.69%,CIA=43~69;∑REE为59.99×10~6~171.07×10~6,∑LREE/∑HREE=6.6~8.8;LaN/YbN=6.6~10.7,LaN/SmN=3.2~4.6,δEu=0.59~1.04。砂岩地球化学特征指示马尔争组复理石岩系形成于沟弧盆系活动大陆边缘构造环境,砂岩属大陆岛弧型,物源区为北侧东昆仑地块火山~深成岩浆岛弧造山带及变质基底,源岩为长英质火山岩、同源深成侵入岩及基底变质岩,沉积盆地为俯冲杂岩外侧的古海沟环境。它间接地记录了阿尼玛卿—布青山古特提斯洋的持续扩张—向北俯冲消减—洋盆闭合的过程。  相似文献   

2.
大兴安岭南段兴-蒙草原区二叠纪砂岩物源分析   总被引:2,自引:1,他引:1  
对大兴安岭南部兴-蒙草原区二叠纪砂岩的统计研究表明,本区二叠纪砂岩主要为长石岩屑砂岩,大量非成熟组分为该区二叠纪砂岩的形成提供了物源。主量、微量和稀土元素特征指示,二叠纪砂岩物源区的构造背景主要为大陆岛弧环境,砂岩碎屑来自上地壳长英质源区。二叠纪砂岩的时代由老到新表现出由再旋回造山带向切割岩浆弧源区过渡的特征。结合沉积学特征,反映中、晚二叠世构造背景由活动陆缘逐渐趋于稳定,该时期记录了中亚造山带东段最终闭合的过程。  相似文献   

3.
库鲁克塔格南华系记录了塔里木北缘同期的火山-沉积事件和蚀源区物质组成及演化的信息。该区不同剖面内南华系各组砂岩碎屑组分的统计分析显示,贝义西组砂岩在不同剖面内组成差异显著:西山口剖面以岩屑砂岩为主,且岩屑为火山岩岩屑与沉积岩岩屑,物源为再旋回地层,而依格孜塔格剖面以长石砂岩和岩屑长石砂岩为主,岩屑主要为变质岩岩屑,物源为下伏古元古代高级变质岩。砂岩碎屑组成在剖面上垂向的变化表明贝义西组沉积期与照壁山组沉积期间(725 Ma±)存在一个沉积转型事件,导致贝义西组之上的照壁山组、阿勒通沟组及特瑞艾肯组砂岩组成在不同区域趋于一致,转变为代表基底隆起-过渡大陆区物源的典型“长石砂岩”。南华系砂岩碎屑组成与大陆裂谷盆地沉积砂岩相似,且物源区存在由前裂谷地层-过渡裂谷肩部-切割裂谷肩部-克拉通内部的连续演化过程,是库满凹陷早期裂解的岩相学记录。  相似文献   

4.
为研究东昆仑南缘中下二叠统马尔争组沉积物源及沉积构造背景,对东昆仑南缘哥日卓托地区中下二叠统马尔争组进行了详细的沉积地层划分、沉积环境及碎屑锆石U-Pb年代学进行了研究。结果表明,马尔争组为一套形成于大陆斜坡半深海-深海环境的浊积岩系。碎屑锆石U-Pb年龄谱可明显划分为早古生代和新元古代两个主年龄谱及古、中元古代两个次级年龄谱。主年龄谱分别为396~573Ma和727~947Ma,峰值年龄分别为421 Ma和862Ma。次级年龄谱分别为1117~1993Ma和2319~3063Ma,峰值年龄不明显。本文认为东昆仑南缘哥日卓托地区马尔争组物质来源较为复杂,显示早古生代、新元古代、中元古代和古元古代多个时代物源共同供给的特征。东昆仑造山带早古生代岩浆岩和新元古代岩浆岩为其提供了约60~65%的沉积物源,而古老的变质基底为其提供了仅约30~35%的沉积碎屑。综合区域资料认为马尔争组形成于相对稳定的被动大陆边缘沉积构造背景,该期阿尼玛卿古特提斯洋还未开始向北俯冲。  相似文献   

5.
东昆仑南缘上二叠统(乐平统)格曲组为一套由砾岩、砂岩和钙质泥岩构成的扇三角洲-浅海碳酸盐台地相沉积组合,记录了东昆仑造山带海西-印支过渡期构造演化过程,是解析该构造演化过程的理想对象。通过分析花石峡北坦地克借地区格曲组碎屑岩的碎屑组成与主量、微量和稀土元素特征,探讨了其物源区属性。结果显示,砂岩类型为长石砂岩和岩屑长石砂岩,石英、长石和岩屑平均含量分别为50.9%、36.8%、12.4%,长石以钾长石为主,岩屑和砾石成分复杂。砂岩的SiO2、Al2O3、TiO2、TFe2O3、MgO、K2O和Na2O平均百分含量分别为62.06%、13.26%、0.44%、4.53%、3.02%、2.42%和3.18%;微量元素比值Th/Sc和Th/U较高,平均为1.06和7.71;稀土元素总量∑REE平均120.43×10-6,LREE/HREE和(La/Yb)N均值分别为9.34和12,轻稀土相对富集,δEu平均为0.96,Eu异常不明显,REE特征与大陆岛弧背景区杂砂岩相似,与东昆仑地体加里东期俯冲-碰撞型火山弧花岗岩具有亲缘性。碎屑组分和主量、微量元素特征与判别图解揭示,格曲组砂岩物源区为海西旋回早期从东昆仑地体裂离的东昆南微地块,源岩以花岗岩为主,变质岩、沉积岩和酸性-基性火山岩较少,其中花岗岩形成构造背景为加里东期的大陆岛弧。结合区域地质和前人研究成果,认为格曲组为前陆盆地系统的隆后盆地沉积。  相似文献   

6.
敦煌造山带南部红柳峡混杂带基质的研究,为认识敦煌造山带的形成和演化提供了新的依据。本文从沉积学、地球化学和年代学等方面系统讨论了该混杂带基质的特征和形成环境。结果显示,基质的岩石类型主要包括变泥质岩(云母石英片岩)和变质砂岩,普遍发生强烈变形。局部弱变形变质的基质仍保留有原生沉积构造(如T_(ab)、T_(de)、T_(bde)组合的鲍马序列),反映原岩是一套浊积岩复理石。显微岩相学特征显示,基质碎屑组分以长石、石英和岩屑为主,长石和岩屑含量较高,分别为47%和27%,反映大量火成岩物质的加入,且碎屑颗粒的分选性和磨圆度较差,说明搬运距离较近。地球化学方面,低的化学蚀变指数(CIA=49~67),反映复理石基质物源区母岩经历的风化程度较低。高的成分变化指数(ICV0.8)以及Zr/Sc-Th/Sc投图结果显示,沉积物再循环程度低,为近物源区的初次沉积。基质Sc、Cr、Co、Ni含量低,Eu/Eu*、La/Sc、Th/Sc、La/Co、Th/Co和Cr/Th等元素比值类似于来自长英质源区的沉积物,暗示其物源区母岩以中-酸性岩石为主。La/Sc-Ti/Zr和Th-ScZr/10投图结果显示,复理石基质形成于陆缘弧或活动大陆边缘构造背景。弱变形浅变质砂岩的碎屑模式表明,基质的物源来自"切割型弧-过渡型弧"源区。综上,红柳峡混杂带基质在碎屑组成方面,以再循环程度低、近物源堆积的"切割型弧-过渡型弧"源区长英质碎屑组分为主,在沉积构造方面,发育鲍马序列和深水块体搬运沉积(MTD)构造,表明基质形成于陆缘弧或活动大陆边缘的俯冲带海沟环境。碎屑锆石年代学显示三组年龄:2300Ma、1850Ma和423Ma,结合区域地质背景分析,初步认为物源碎屑可能来自混杂带北侧的三危山弧和东巴兔-蘑菇台弧的古生代花岗岩类以及俯冲折返的变质基性岩岩块。复理石基质的变质砂岩中获得的最年轻的岩浆碎屑锆石年龄为389Ma,说明该砂岩形成于中泥盆世之后,暗示敦煌造山带南部红柳峡地区洋盆尚未俯冲完毕,碰撞作用尚未开始。  相似文献   

7.
为了判断太原西山煤田物源区,并探讨物源区构造背景,运用砂岩单碎屑组分法、多碎屑组分法和重矿物组合法,综合分析了七里沟剖面二叠系下石盒子组底部骆驼脖子砂岩的特征。结果表明:骆驼脖子砂岩主要组分为石英和岩屑,石英占80%以上,岩屑占10%左右,长石极少见,体积分数小于1%,且石英和岩屑成因类型以岩浆岩型和变质岩型为主,沉积岩型含量较少;重矿物主要由锆石、磷灰石和金红石组成,揭示出物源区母岩类型为酸性岩浆岩,物源区为北面阴山古陆,砂岩组分的Dickinson三角图解表明,物源区构造背景为再旋回造山带。   相似文献   

8.
为了探究广西十万大山盆地扶隆坳组地球化学特征及其地质意义,在显微镜下对研究区砂岩进行了系统鉴定、碎屑颗粒组分统计,并利用ICP-MS对该区泥岩样品进行了微量元素和稀土元素分析,结果显示扶隆坳组砂岩碎屑颗粒组分石英颗粒含量较高,长石含量较少,岩屑以浅变质岩屑为主,Dickinson图解显示物源区为再旋回造山带;泥岩样品的REE受成岩作用改造微弱,且主要来自陆源碎屑矿物,源岩主要为沉积岩及花岗岩岩石;稀土元素和微量元素相关参数显示晚三叠世扶隆坳沉积时期气候相对湿热,沉积了一套以陆相沉积环境为主的碎屑岩。综合前述认识,结合本区构造演化史,推断扶隆坳组物源供给主要来自晚泥盆世-早石炭世钦防海槽沉积的硅质岩、硅质页岩及泥岩,源区构造背景兼有活动大陆边缘和被动大陆边缘的性质。  相似文献   

9.
夏飞勇  焦养泉  荣辉  吴立群  朱强  万璐璐 《地球科学》2019,44(12):4235-4251
沉积物的地球化学成分在沉积岩物源分析及构造背景的研究中具有重要的作用.对研究区4口钻孔中的姚家组砂岩进行了详细的岩石学和地球化学研究,结果显示,砂岩碎屑颗粒石英含量最高,长石次之,岩屑含量最低,平均值分别为42%、37%和21%,具有锆石+钛磁铁矿+石榴子石的重矿物组合,反映源岩以酸性岩浆岩或变质岩为主,Dickinson判别图解表明物源主要来自于大陆物源区;姚家组砂岩的稀土元素以轻稀土富集、重稀土平坦、中度铕负异常为特征.砂岩CIA值为52.02~60.16,平均值为56.69,反映了干燥气候背景下弱的化学风化作用.源岩属性判别图解表明源岩为再旋回的古老沉积物及长英质火山岩.主量、微量和稀土元素的构造背景判别图解综合表明姚家组砂岩物源区为被动大陆边缘构造环境,结合区域构造演化,认为姚家组砂岩的物源为华北克拉通北缘燕山陆内造山带发育的火山-沉积岩系.   相似文献   

10.
赞比亚东北部伊鲁米德带是一个北东向延伸的中元古代构造活动带,起自赞比亚中部,向北东一直延伸至赞比亚-坦桑尼亚边境,并进入马拉维北部;其东北部以古元古代乌本迪构造带为界;西北部以班韦乌卢地块为界;西部和西南部受新元古代的达马拉-卢菲利安弧-赞比西构造事件的影响.Kachinga长石砂岩位于伊鲁米德带的东北部伊索卡南部.本文获得Kachinga长石砂岩的416颗碎屑锆石U-Pb年龄多集中在1749±25~1920±23Ma之间,Kachinga长石砂岩的形成时代可能晚于1331±26Ma,属于中元古代.Kachinga长石砂岩碎屑锆石CL图像表明,大部分锆石为岩浆结晶锆石,少部分锆石颗粒为增生-混合型锆石,表明其经历了多期构造-热事件的改造.锆石中存在有一部分磨圆度较好的颗粒,表明其经历了多次搬运和沉积过程,从而指示了古老沉积岩为Kachinga长石砂岩提供了物源.主量元素、微量元素和稀土元素构造环境判别及物源分析表明了Kachinga长石砂岩物源主要为上地壳大陆长英质源区,并且可能混有古老沉积物成分,物源区构造背景为大陆岛弧环境.  相似文献   

11.
Characteristic meniscus geometries formed by kaolinitic infiltration are observed in Nubian sandstones collected on the western coast of the Sinai Peninsula (Egypt). Based on petrographic and scanning electron microscope (SEM) observations, the kaolinite forming the menisci consists of mixed-size discrete platelets that gather into the corners around the framework grain-to-grain contacts. Specifically, the internal fabric of menisci indicates a general organizing trend from (1) the centre, where the platelets coat the framework grains; (2) to the peripheral zone, where they are oriented tangentially to grain surfaces; (3) to the pore linings with curvatures that are consistent with theoretical considerations of air–water interfaces. This typical arrangement suggests a detrital origin of kaolinite platelets by mechanical infiltration into sediments lying above the tablewater, in vadose conditions. This type of clay cementation occurring during early diagenesis can prevent (delay) deep burial diagenetic processes and therefore preserve excellent reservoir properties.  相似文献   

12.
四川沐川石英砂岩精制提纯研究   总被引:1,自引:0,他引:1  
谭靖  王雷  杨林 《贵州地质》2010,27(4):312-316
在工艺矿物学研究的基础上,采用相应的提纯工艺,进行精制石英砂提纯探索试验,使矿石中SiO2品位由93%左右提高至99.0%以上,为提升该矿的利用价值提供技术支持。  相似文献   

13.
Flexible quartzitic rocks are found in various locations around the world and have been identified as both sandstones and quartzites. The term itacolumite was first used for a Brazilian quartzite thought to be a new type of rock in 1822. As analytical methods have improved flexibility has been shown to be due to irregular interlocking quartz grains surrounded by regular intergranular spaces. Platy minerals such as muscovite are sometimes present and probably add support to the structure, but are not necessary for flexibility. The underlying cause of the texture appears to be chemical dissolution of quartz at the grain boundary.  相似文献   

14.
尼日尔特吉达地区砂岩中铀的热流体成矿作用   总被引:3,自引:0,他引:3       下载免费PDF全文
通过野外详细地质调查、钻孔观察、岩芯编录、地质现象素描等方法, 结合室内工作及前人的研究成果, 对尼日尔特吉达地区的铀矿化的研究成果显示, 特吉达地区砂岩中铀主要为热流体成矿, 与前人的氧化带成矿作用认识完全不同。区内主要含矿目的层(白垩世早期阿萨乌阿组)为中粒—中粗粒石英砂岩、长石石英砂岩, 多数含砾。根据阿萨乌阿组砂岩的磨圆、分选好和发育向上变粗序列以及冲洗交错层理等特征确定, 阿萨乌阿组形成于湖滨浅湖砂坝沉积。电子探针成分和背散射电子图像分析表明: 铀矿物主要为沥青铀矿、铀石、吸附铀等, 沥青铀矿和铀石常紧密共生, 呈粒状、微脉状或浸染状, 伴有较强的铜矿化。热流体蚀变形成的方解石、棕色方沸石、绢云母等大量出现, 它们与铀成矿关系密切。成岩期的菱铁矿在后来的氧化中形成赤铁矿/针铁矿(褐铁矿)化。根据与方解石共生的白云石的摩尔数计算的方解石的形成温度表明, 最高温度为385℃, 最低为178℃, 平均为251~300℃。  相似文献   

15.
区内砂岩中的粘土矿物主要是自生的高岭石、绿泥石和伊蒙混层,而泥岩中的粘土矿物是伊蒙混层和高岭石,少量绿泥石。未见蒙脱石。砂岩和泥岩中粘土矿物的转化具有相似的水介质和地温条件,都反映出在中—晚成岩期形成,而且与烃类的排出和运移密切相关。泥岩中粘土矿物转化和脱水作用为砂岩输送流体和释放溶解物质。而且泥岩中有机质的脱羟基向砂输送酸性水,促进砂岩中骨架颗粒溶解、次生孔隙的产生。  相似文献   

16.
通过对研究区下白垩统南屯组沉积时期重矿物组合、砂岩组合和地震反射特征资料的综合研究,确定了沉积物的物源方向和砂体展布特征。研究发现同生断裂组合对砂体起到了分散及阻挡的作用,根据同生断裂的组合以及与砂体的制约关系,划分出掀斜型阶梯状、未掀斜型阶梯状和极性3种类型的控砂断裂组合。并根据物源特征和砂体展布特征,将控砂断裂组合分为"横向砂体"和"纵向砂体"2种砂体展布类型;综合各类断裂组合对砂体的控制作用,总结出"诱导型"和"遏制型"两种控砂机制模式。本次研究对在断陷湖盆开展构造对沉积控制作用及分散机制研究提供一个实例。  相似文献   

17.
Giant calcite-cemented concretions, Dakota Formation, central Kansas, USA   总被引:1,自引:0,他引:1  
Giant spheroidal concretions (cannonball concretions; some nearly 6 m in diameter) in fluvial channel‐fill sandstones at two localities of the Dakota Sandstone formed by import of cement constituents at a burial depth of <1 km. During cannonball concretion growth a self‐organizational process restricted concretions to a relatively few but widely spaced, and locally, evenly spaced, sites. Other forms of calcite cements at these localities are cement patches in the form of intergrown grape‐size concretions (grapestone), and, locally, pervasive cement. An early episode of invasion by thermogenically generated H2S, which reacted with iron oxides on detrital grains, generated scattered pyrite crystals and decimetre‐scale spheroidal pyrite concretions. Intergranular volumes (IGV) in the concretions range from 36% to 27%. The absence of a trend in IGV and of carbon and oxygen‐isotope ratios from cannonball centres to margins indicates that these concretions did not cement progressively outwards from the centre. Rather, the modern spheres represent the spatial extent of nucleation sites that were not otherwise organized within that volume. Carbon and oxygen‐isotope values for concretion calcites plot along a swath between depleted values of δ18C of ?36‰ and δ18O of ?13‰ and enriched values of ?4‰ and ?6‰, respectively. Four groups of calcites are evident on the basis of trace‐element content and suggest that the calcite precipitated across a range of oxidation conditions that do not correlate strongly with the isotopic compositions. Although fluvial overbank sandstones have some pedogenic calcite, the channel sandstones have at most a trace of pedogenic calcite and carbonate rock fragments, so that the bulk of cement components were imported to the sandstones. Carbon and calcium sources for calcite cement include marine limestone, carbonate shells, and anhydrite in addition to HCO derived from oxidized methane, most likely derived from beds underlying or laterally in communication with Dakota sandstones. HCO in ascending formation waters, released during compaction, mixed with meteoric water whose temperature and composition varied with time, to generate the 7‰ range in δ18Ocalcite values measured.  相似文献   

18.
川西洛带气田蓬莱镇组中上部的储层特征   总被引:1,自引:0,他引:1       下载免费PDF全文
洛带气田蓬莱镇组中上部天然气藏的储层主要为三角洲前缘的水下分流河道、河口砂坝、水下决口河道和远砂坝微相砂体.储集空间以粒间孔和粒内溶孔为主.储集岩的孔隙度一般为8%~16%,渗透率均值为1.970×10-3μm2,属低中孔隙度、低渗透率储层.储渗性主要受方解石、硬石膏、长石含量和粘土矿物的影响.沉积微相控制了储层砂体的类型和展布特征.根据区内储集岩的岩石学特征、物性参数和孔喉结构特征,将其划分为四种类型.  相似文献   

19.
This article presents a systematic analysis of the anisotropic behaviours of the Bentheim and Rothbach sandstones using ultrasonic P-wave velocity, electrical conductivity and magnetic susceptibility measurements. For each sandstone, the data were obtained from three core samples drilled perpendicularly to each other and tested in dry- and water-saturated conditions. For acoustic and magnetic investigations, the same statistical analysis was applied in order to present the data on comparable stereoplots. Surprisingly, the Bentheim sandstone which appeared homogeneous at macroscopic scale showed a stronger elastic and electrical anisotropy than the Rothbach sandstone in which cross-laminations were clearly identified, as confirmed by a sedimentary magnetic fabric. A discussion on the velocity contrasts between dry and saturated samples led us to consider two different origins for the observed anisotropies. First, by comparing electrical and acoustic properties in the Bentheim sandstone, we conclude that the nature of the anisotropic behaviour is linked to the anisotropy of pore shape: the inclusion model developed by Kachanov (Kachanov, M., 1993. Elastic solids with many cracks and related problems. Advances in Applied Mechanics, vol. 30. Academic Press, Boston, MA, pp. 259–445) accounts for our observations if one considers that the pore space is made of parallel flat pores with moderate pore aspect ratio. Second, acoustic, electrical and magnetic properties indicate that the observed anisotropy in the Rothbach sandstone can be attributed to the matrix, and more specifically to cementation: we modified the Dvorkin and Nur (Geophysics 61 (5) (1996) 1363) model of cemented granular media by introducing a spatially variable contact length, and the model suggests that a very small variability of cemented contact length is enough to account for the observed P-wave velocity anisotropy. We emphasise the fact that combining several kinds of measurements is of great help in capturing the nature of the anisotropic behaviour of porous rocks.  相似文献   

20.
矿区高岭土严格受岩性和地层层位控制。矿石含矿率高。质量好,矿物组成主要为高岭石和石英,其次有伊利石,高岭石为自形的假六方片状晶体,有序度高,晶体粒度细,伊利石多属边界圆滑的等度片状晶体。矿床的形成经历了原始的沉积阶段和成岩改造阶段,为“沉积改造”成因。  相似文献   

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