塔里木盆地寒武-奥陶系白云岩结构构造类型及其形成机理   总被引：10，自引：4，他引：6  

吴仕强  朱井泉  王国学  胡文瑄  张军涛  王小林 《岩石学报》2008,24(6):1390-1400

塔里木盆地寒武-奥陶系白云岩度大、分布广,是重要的油气储集层.根据岩石学研究并结合地球化学特征将其分为4类,其特点如下:(1)泥晶-粉晶白云岩,白云石晶体小、晶形差,有序度在4类中最低(0.73);Na、K、Sr含量在4类中最高;δ13C值及Z值较高,分别为-0.94‰、122.3;Fe、Mn含量较低;阴极发光为亮桔红色;常呈纹层状,具暴露及成化标志.这些特征表明其结晶较快,形成环境蒸发强烈、盐度较高、氧化性较强,是在萨布哈环境中由浓缩海水发生白云石化所形成.(2)藻纹层白云岩,白云石晶体小,晶形较好,有序度较高(0.85);藻纹层基本保留了其原始微细结构;Na、K、Sr含量较低:δC值在4类中最高,平均为-0.50‰;含有较多黄铁矿.这些特征说明其可能形成于成岩作用的稍早期阶段且其成因与藻类活动密切相关,成岩环境盐度较低,可能是在藻类作用下,由富藻层浓集的镁与残留海水在浅埋藏环境中共同作用所形成.(3)雾心亮边白云岩,白云石普遍具雾心亮边结构,雾心含少量包裹体及灰质残余,亮边则少见或无;阴极发光下,雾心发亮桔黄色光,亮边发光暗或不发光;局部见此类白云石;呈星散状分布于亮晶颗粒灰岩或泥晶灰岩中;白云石晶体较大,晶形较好.此类白云岩的δ13C及Z值在4类中最低,K、Na、Sr、Fe含量相对较低,Mn含量最高;有序度较高,均值为0.83.这些特征表明此类白云岩中白云石的雾心可能是在早期浅埋藏环境中,由富镁孔隙水交代周围灰质所形成;亮边则形成于埋藏较深的环境,其所需镁可能来源于粘土矿物的转化.(4)重结晶白云岩:白云石晶体粗大且污浊,接触紧密;局部见白云石晶体具环带结构,局部见颗粒幻影结构;阴极发光较暗;Fe含量在4类中最高,Mn含量较高;有序度最高,平均为0.95;包裹体均一温度平均为110.2℃.这些特征表明其可能是在还原性较强的深埋藏环境中,由早期形成的白云岩经较强的重结晶作用所形成.  相似文献   

The bimodal composition of carbonatites: Reality or misconception?     

J. Gittins  R.E. Harmer  D.S. Barker   《Lithos》2005,85(1-4):129-139

The concept of compositional bimodality in carbonatites has become widely accepted and has been used to impose restrictions on the composition of carbonatite magmas. We agree that mineralogical bimodality exists in carbonatites (most are either calcitic or dolomitic/ankeritic), but we argue that there is no compositional bimodality. The idea of bimodality is based on the interpretation of a variety of element distribution diagrams which were compiled only from chemical analyses in which SiO₂ is < 10 wt.%. All others were rejected. Even with such a restricted data set the case for compositional bimodality is extremely weak, but the inclusion of analyses with higher SiO₂ content destroys it completely. Yet these more siliceous compositions must be included, for many carbonatites contain substantial amounts of Fe–Mg silicates which are an essential part of the magmatic mineralogy of the rocks. They account for much of the Mg in carbonatites that are otherwise calcitic. Many such carbonatites contain well in excess of 10 wt.% SiO₂. Supporters of the bimodality concept argue that liquids having compositions between calcite and dolomite can precipitate neither calcite nor dolomite because the minimum on the solid solution loops in the system calcite–dolomite permits only a carbonate of intermediate composition. Therefore, it is argued, liquids of such intermediate composition cannot be parental to calcitic and dolomitic carbonatites; their parent magmas must be calcitic and dolomitic. This deduction is incorrect. It is well established that dolomitic liquids have calcite as the liquidus phase over substantial temperature intervals, and that this is followed by dolomite precipitation. Mixed calcite–dolomite carbonatites are explicable in this way. Therefore, dolomitic liquids can be parental to calcitic carbonatites. However, dolomitic carbonatites cannot crystallize from a calcitic liquid. We suggest that intermediate composition carbonatite magmas are probably common. Bimodality in carbonatites is solely mineralogical, not compositional.  相似文献   

塔里木盆地和田河气田周缘寒武系盐下白云岩油气勘探潜力分析          下载免费PDF全文

曾昌民 李 勇范秋海  冯晓军张 亮 陈 才朱礼春  陈延贵李向云 《地质科学》2018,(4):1413-1439

塔里木盆地塔西南地区和田河气田周缘寒武系中统发育厚层膏盐岩,其下白云岩溶蚀裂缝-孔洞型储层发育条件好。多个层系具备烃源岩发育条件,除寒武系下统玉尔吐斯组外,震旦系、南华系也是可能的重要生油层系,油气资源丰富。盐下发育多个规模较大的构造圈闭,且由于膏盐岩层的滑脱作用,断裂很难断穿盐层,后期保存条件好。因此,寒武系中统膏盐岩与下伏白云岩组成本区重要的储盖组合,勘探领域具有非常好的前景。  相似文献   

四川盆地东北部三叠系飞仙关组碳酸盐岩成岩作用和白云岩成因的研究现状和存在问题   总被引：10，自引：0，他引：10  

黄思静  Hairuo QING  胡作维  王春梅  郜晓勇  邹明亮  王庆东 《地球科学进展》2007,22(5):495-503

四川盆地东北部三叠系飞仙关组是我国重要的天然气储集层，优质储层形成机制直接与碳酸盐岩成岩作用、尤其是白云岩化作用相关，但飞仙关组碳酸盐岩在锰含量、锶含量、阴极发光性等特征上反映其成岩过程与经典成岩理论相悖；碳酸盐岩的锶同位素组成和锰、锶含量的关系也表明与大气水有关的成岩过程和作为重要储集岩的结晶白云岩的形成机制无关，传统的白云岩化机制难以解释结晶白云岩的成因。具有海源色彩的高锶、低锰成岩流体在很大程度上控制了飞仙关组碳酸盐的成岩作用，其来源与成因值得进一步关注，控制其运移、封存和发生水—岩反应的时空机制有待回答。整个海相三叠纪时间段盆地尺度碳酸盐岩和蒸发岩的沉积地球化学研究、尤其是不同结构组分碳酸盐的锶同位素组成、锶和锰含量研究（包括碳酸盐岩中不同结构组分的阴极发光性研究），可为四川盆地东北部飞仙关组碳酸盐岩成岩作用（尤其是白云岩化作用和作为重要储集岩的结晶白云岩的成因研究），天青石矿床成因研究和四川盆地三叠系深层富钾、锶、硼、溴卤水的成因研究提供重要的线索。  相似文献   

白云鄂博矿床白云岩的Sm—Nd、Rb—Sr同位素体系   总被引：17，自引：4，他引：17  

张宗清  唐索寒  王进辉  袁忠信  白鸽 《岩石学报》2001,17(4):637-642

白云鄂博矿床的年龄和成因长期争论.本文报道了白云鄂博矿床白云岩及其组成矿物的Sm-Nd、Rb-Sr同位素分析结果.采自该矿床主、东矿等地的15个白云岩样品的Sm-Nd同位素分析结果呈现一条等时线,等时年龄1273±100(2σ)Ma,INd=0.510919士36(2d),MSWD1.01.全岩Rb-Sr同位素分析结果分散,不构成等时线.87Rb/86Sr0～2.092×100-2,87Sr/86Sr0.70341～0.70541.白云岩矿物的Sm-Nd同位素分析结果给予了与全岩类似的Sm-Nd等时年龄,t=1250士210(2σ)Ma,1Nd=0.510914±77(2σ),MSWD 0.56.白云鄂博矿床可能是中元古代末期大离子亲石微量元素略为富集地幔源区部分熔融岩浆活动产物.  相似文献   

Petrographic and geochemical evidence for the formation of primary, bacterially induced lacustrine dolomite: La Roda 'white earth' (Pliocene, central Spain)   总被引：1，自引：0，他引：1  

M. Angeles García Del Cura  Jose P. Calvo  Salvador Ordóñez  Blair F. Jones  & Juan C. Cañaveras 《Sedimentology》2001,48(4):897-915

Upper Pliocene dolomites (‘white earth’) from La Roda, Spain, offer a good opportunity to evaluate the process of dolomite formation in lakes. The relatively young nature of the deposits could allow a link between dolomites precipitated in modern lake systems and those present in older lacustrine formations. The La Roda Mg‐carbonates (dolomite unit) occur as a 3·5‐ to 4‐m‐thick package of poorly indurated, white, massive dolomite beds with interbedded thin deposits of porous carbonate displaying root and desiccation traces as well as local lenticular gypsum moulds. The massive dolomite beds consist mainly of loosely packed 1‐ to 2‐μm‐sized aggregates of dolomite crystals exhibiting poorly developed faces, which usually results in a subrounded morphology of the crystals. Minute rhombs of dolomite are sparse within the aggregates. Both knobbly textures and clumps of spherical bodies covering the crystal surfaces indicate that bacteria were involved in the formation of the dolomites. In addition, aggregates of euhedral dolomite crystals are usually present in some more clayey (sepiolite) interbeds. The thin porous carbonate (mostly dolomite) beds exhibit both euhedral and subrounded, bacterially induced dolomite crystals. The carbonate is mainly Ca‐dolomite (51–54 mol% CaCO₃), showing a low degree of ordering (degree of ordering ranges from 0·27 to 0·48). Calcite is present as a subordinate mineral in some samples. Sr, Mn and Fe contents show very low correlation coefficients with Mg/Ca ratios, whereas SiO₂ and K contents are highly correlated. δ¹⁸O‐ and δ¹³C‐values in dolomites range from ?3·07‰ to 5·40‰ PDB (mean=0·06, σ=1·75) and from ?6·34‰ to ?0·39‰ PDB (mean=?3·55, σ=1·33) respectively. Samples containing significant amounts of both dolomite and calcite do not in general show significant enrichment or depletion in ¹⁸O and ¹³C between the two minerals. The correlation coefficient between δ¹⁸O and δ¹³C for dolomite is extremely low and negative (r=?0·05), whereas it is higher and positive (r=0·47) for calcite. The lacustrine dolomite deposit from La Roda is interpreted mainly as a result of primary precipitation of dolomite in a shallow, hydrologically closed perennial lake. The lake was supplied by highly saturated HCO₃^?/CO₃^2? groundwater that leached dolomitic Mesozoic formations. Precipitation of dolomite from alkaline lake waters took place under a semi‐arid to arid climate. However, according to our isotopic data, strong evaporative conditions were not required for the formation of the La Roda dolomite. A significant contribution by bacteria to the formation of the dolomites is assumed in view of both petrographic and geochemical evidence.  相似文献   

Methane-induced dolomite “chimneys” on the Kuroshima Knoll, Ryukyu islands, Japan     

Rika Takeuchi  Ryo Matsumoto  Shigenori Ogihara  Hideaki Machiyama 《Journal of Geochemical Exploration》2007,95(1-3):16

The Kuroshima Knoll is about 26 km south of Ishigaki Island in the southern part of the Ryukyu Arc. The area is considered to be the source area of “The 1771 Yaeyama Earthquake Tsunami”, which was due to the submarine landslide caused by an earthquake. It has been cleared from some investigations using “Dolphin 3K” and “Shinkai 2000” that there are large-scale dead Calyptogena colonies, many gravels of fallen dolomite chimneys and carbonates on the top of the Knoll [Matsumoto, T., Uechi, C., Kimura, M., 1997; Machiyama, H., Matsumoto, T., Matsumoto, R., Hattori, M., Okano, M., Iwase, R., Tomaru, H., 2001b.]. Carbonates of Kuroshima Knoll have various shapes and macroscopic textures. These have been classified into 4 types; shell crust (pavement), chimney, burrow, and nodule. It is clear that all chimney and burrow carbonates are composed of dolomite, while shell curst and nodule are composed of calcite, sometimes both calcite and dolomite. These carbonates are considered to have been formed by cold seep, because they are characterized by the light carbon isotopic ratio (semi-biogenic) and the heavy oxygen isotopic ratio. This suggests that methane hydrate layers develop under this survey area and the water that has the heavy oxygen and the light carbon isotopic ratio is derived from the dissociation of methane hydrate.  相似文献   

辽东半岛南部早古生代馒头组—冶里组沉积盆地演化     

单学东  李显东  战丽华  董洪年 《国土资源》1998,(3)

辽东半岛南部早古生代地层发育,其中馒头组—冶里组的沉积过程,具有完整的陆源碎屑岩—碳酸盐岩堆积特点。从层序划分、沉积环境演化、古气候变迁等方面分析,馒头组—冶里组反映了一个完整的碳酸盐岩台地的发展过程,可划分出准备阶段（形成碎屑岩垫板）、生长—发育阶段（形成碳酸盐岩缓坡）及衰亡阶段（发育白云岩盖层）。  相似文献   

白云鄂博矿区周围火成碳酸岩岩墙地质特征   总被引：19，自引：0，他引：19       下载免费PDF全文

陶克捷  王文志 《地质科学》1998,33(1):73-83

首次填出白云鄂博矿区周围火成碳酸岩岩墙的分布图,深入系统地研究了岩墙的地质产状、主矿物类型、岩石结构、人工重砂矿物组成、稀土元素含量等特征。反映了白云鄂博矿区周围火成碳酸岩岩墙的岩浆演化分异过程存在差异。对于研究白云鄂博矿区铁与稀土的矿化提供了物质来源的证据。  相似文献   

鄂尔多斯盆地中部气田奥陶系马五1层的古岩溶作用与天然气富集     

傅强  王家林 《海相油气地质》1998,3(2):29-33

鄂尔多斯盆地中部气田的储层为奥陶系马家沟组白云岩风化壳,马五１层为其主力气层,该层可分为四个小层,沉积相为分布稳定的蒸发潮坪环境,经历了表生期和浅、深埋藏期岩溶作用,天然气主要聚集在岩溶孔洞缝中。  相似文献