Age,composition, and source of continental arc- and syn-collision granites of the Neoproterozoic Sergipano Belt,Southern Borborema Province,Brazil     

《Journal of South American Earth Sciences》2015

The Sergipano belt is the outcome of collision between the Pernambuco-Alagoas Domain (Massif) and the São Francisco Craton during Neoproterozoic assembly of West Gondwana. Although the understanding of the Sergipano belt evolution has improved significantly, the timing of emplacement, geochemistry and tectonic setting of granitic bodies in the belt is poorly known. We recognized two granite age groups: 630–618 Ma granites in the Canindé, Poço Redondo and Macururé domains, and 590–570 Ma granites in the Macururé metasedimentary domain. U–Pb SHRIMP zircon ages for granites of first age group indicated ages of 631 ± 4 Ma for the Sítios Novos granite, 623 ± 7 Ma for the Poço Redondo granite, 619 ± 3.3 Ma for the Lajedinho monzodiorite, and 618 ± 3 Ma for the Queimada Grande granodiorite. These granitoids are dominantly high-K calc-alkaline, magnesian, metaluminous, mafic enclave-rich (Queimada Grande and Lajedinho), or with abundant inherited zircon grains (Poço Redondo and Sitios Novos). Geochemical and isotope data allow us to propose that Sítios Novos and Poço Redondo granites are product of partial melting of Poço Redondo migmatites. Sr-Nd isotopes of the Queimada Grande granodiorite and Lajedinho monzodiorite suggest that their parental magma may have originated by mixing between a juvenile mafic source and a crustal component that could be the Poço Redondo migmatites or the Macururé metasediments. Other 630–618 Ma granites in the belt are the mafic enclave-rich Coronel João Sá granodiorite and the Camará tonalite in the Macururé sedimentary domain. These granites have similar geochemical and isotopic characteristics as the Lajedinho and Queimada Grande granitoids. We infer for the Camará tonalite and Coronel João Sá granodiorite that their parental magmas have had contributions from mafic lower crust and felsic upper crust, most probably from underthrust São Francisco Craton, or Pernambuco-Alagoas Domain. The younger 590–570 Ma granite group is confined to the Macururé metasedimentary domain. Although these granites do not show typical features of S-type granites, their U–Pb age, field relationships, geochemical and Sr-Nd data suggest that their parental magmas have originated from high degree melting of the Macururé micaschists. Field observations support a model in which the Macururé domain, limited by the Belo Monte-Jeremoabo and São Miguel do Aleixo shear zones, behaved as a ductile channel flow for magma migration and emplacement during the Neoproterozoic, very much like the channel flow model proposed for emplacement of leucogranites in the Himalayas.  相似文献   

西准噶尔白杨河铍铀矿床中铍与铀成生关系初探——来自围岩蚀变和矿石矿物接触关系的证据     

刘畅 《地质与勘探》2020,56(3):465-477

与高硅富氟火成岩(流纹岩或花岗斑岩)有关的铍矿床中常伴有铀矿化,其成矿特色明显,是认识岩浆-岩浆热液-热液演化过程中铍与铀地球化学行为异同的理想对象,但其中铍与铀成矿的时空关系及成因关系尚不清楚。为了理解该类矿床中铍与铀的成生关系,并为区域内铍与铀的找矿勘查提供理论支撑,本文选取该类矿床的典型代表—西准噶尔白杨河铍铀矿床为研究对象,通过镜下观察、扫描电镜能谱和激光拉曼光谱分析,对矿区内单铍矿石、单铀矿石和铍铀矿石开展了系统的岩相和矿相学研究。结果显示,与铍矿化相关的围岩蚀变为钠长石化、电气石化、白云母化、萤石化、碳酸盐化和绿泥石化,与铀矿化相关的围岩蚀变为硅化、赤铁矿化、萤石化、伊利石化和锰矿化(含少量铅),且铍铀矿石中可见沥青铀矿切穿羟硅铍石的现象。结合铍与铀的地球化学行为和前人研究成果,认为白杨河铍铀矿床中铍矿化与铀矿化应是不同期热液作用的结果:铍矿化可能是花岗斑岩深部岩浆房分异的岩浆热液在不断演化过程中形成的,而铀矿化可能与后期流体(如幔源流体、加热循环的大气降水等)的淋滤作用有关。  相似文献   

准噶尔西北缘红山嘴地区克上组辫状河三角洲沉积-储层耦合关系与综合定量评价     

高阳  刘文峰  于兴河  杨新涛 《中国地质》2020,47(4):971-984

综合岩心、薄片、分析测试资料厘定辫状河三角洲不同相带储层特征及控制因素,选取孔隙度、含砂率、优势砂厚、优势砂岩分层系数及杂基含量作为评价参数,基于灰色关联法确定权重、拐点法确定分类阈值对储层进行综合定量评价。结果表明辫状河三角洲下平原地区由于储层物性好且优势砂岩(粗砂岩)占比高而Ⅰ类储层发育;三角洲上平原地区砂体发育但以砾岩沉积为主,杂基含量高而储层质量差,多为Ⅱ类储层;三角洲前缘地区正韵律特征显著,中、粗砂岩储层质量要优于细砂岩,但优势砂岩发育规模有限,因此多以Ⅱ类、Ⅲ类储层为主。该成果可为复杂砂砾岩储层的定量评价提供借鉴。  相似文献   

准噶尔盆地南缘头屯河地区砂岩型铀矿铀源区及其成矿构造背景分析——来自碎屑锆石U-Pb年龄及Hf同位素的证据     

耿英英  刘章月  何中波  黄少华  郭强  许强  宋继叶 《地质论评》2020,66(2):393-409

准噶尔盆地是我国重要的多能源矿产产出盆地之一,而准噶尔盆地南缘头屯河地区也是我国砂岩型铀矿找矿的优选区段,为了厘定头屯河地区砂岩型铀矿赋矿层位沉积期的源区位置、母岩岩性及时代,本文在野外地质调查的基础上,对头屯河地区砂岩型铀矿赋矿层中的碎屑锆石进行了LA-ICP-MS U-Pb定年和Hf同位素分析,建立了碎屑锆石的U-Pb年龄及Hf模式年龄谱系。通过与周缘岩浆活动时代对比,并结合古流向数据进一步分析赋矿层位沉积期的源区位置及母岩岩性,讨论砂岩型铀矿的铀源条件。对采自侏罗系和下白垩统的4个砂岩样品进行碎屑锆石年龄分析表明:碎屑锆石U-Pb年龄存在140～180 Ma、240～320 Ma、340～420 Ma、440～480 Ma四个主峰值年龄段,年龄较平均的分布在210～480 Ma宽泛的区间内。研究表明头屯河地区早侏罗世物源来自北天山;中侏罗世物源来自中、南天山;中侏罗晚期开始转变为以北天山为主;早白垩世物源大部分来自中、北天山,少量来自博格达山地区。砂岩型铀矿化层铀源主要来自南侧天山地区的古生代中酸性火成岩,其成矿作用应该发生在盆地处于较稳定的构造环境中。  相似文献   

Coalbed Methane Enrichment Regularity and Major Control Factors in the Xishanyao Formation in the Western Part of the Southern Junggar Basin     

YUAN Yuan  SHAN Yansheng  TANG Yue  CAO Daiyong 《《地质学报》英文版》2020,94(2):485-500

There are abundant coal and coalbed methane(CBM)resources in the Xishanyao Formation in the western region of the southern Junggar Basin,and the prospects for CBM exploration and development are promising.To promote the exploration and development of the CBM resources of the Xishanyao Formation in this area,we studied previous coalfield survey data and CBM geological exploration data.Then,we analyzed the relationships between the gas content and methane concentration vs.coal seam thickness,burial depth,coal reservoir physical characteristics,hydrogeological conditions,and roof and floor lithology.In addition,we briefly discuss the main factors influencing CBM accumulation.First,we found that the coal strata of the Xishanyao Formation in the study area are relatively simple in structure,and the coal seam has a large thickness and burial depth,as well as moderately good roof and floor conditions.The hydrogeological conditions and coal reservoir physical characteristics are also conducive to the enrichment and a high yield of CBM.We believe that the preservation of CBM resources in the study area is mainly controlled by the structure,burial depth,and hydrogeological conditions.Furthermore,on the basis of the above results,the coal seam of the Xishanyao Formation in the synclinal shaft and buried at depths of 700-1000 m should be the first considered for development.  相似文献   

Significant differences in late Quaternary bedrock erosion and transport: East versus West Greenland ∼70°N – evidence from the mineralogy of offshore glacial marine sediments          下载免费PDF全文

JOHN T. ANDREWS  ANDERS A. BJORK  DENNIS D. EBERL  ANNE E. JENNINGS  EMILY P. VERPLANCK 《第四纪科学杂志》2015,30(5):452-463

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秦岭成矿带印支期构造演化与金的成矿关系——以夏河临潭地区为例     

范堡程  杨晓奇  李航  薛仲凯  栾晓刚  董启明  杨宗枫 《地质论评》2024,70(S1):118-120

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Evaluating coastal scenery using fuzzy logic: Application at selected sites in Western Black Sea coastal region of Turkey   总被引：1，自引：0，他引：1  

Ay?en Ergin  Fatma ?ahin 《Ocean Engineering》2010,37(7):583-591

Coastal areas of the world are under treat due to the conflicting requirements of functions such as habitation and/or recreation, which affect the strategic asset of coastal scenery itself. Coastal managers, together with planners, need coastal landscape inventories, where the quality of coastal scenery is a part of the inventory. In order to provide an evidence-based approach for sound coastal management decisions, [Ergin et al., 2004] and [Ergin et al., 2006] developed a novel technique ‘coastal scenic evaluation’ (CSE), which addresses the evaluation of coastal scenery. The CSE technique utilizes fuzzy logic to derive values obtained from a checklist of 26 physical and human parameters. The methodology enables the calculation of an evaluation index (D), which categorizes the scenic values of coastal sites into five distinct classes. Using this technique, coastal scenic evaluations were carried out at 34 selected sites on the Western Black Sea coast of Turkey. Based on the calculated D values, a five-class differentiation was obtained for the selected sites, to provide baseline information for any envisaged subsequent management plans for these areas.  相似文献   

Thermal regime of the northwest Indian rifted margin – Comparison with predictions     

Gérôme Calvès  Anne M. Schwab  Mads Huuse  Peter D. Clift  Asif Inam 《Marine and Petroleum Geology》2010

We use a simple approach to estimate the present-day thermal regime along the northwestern part of the Western Indian Passive Margin, offshore Pakistan. A compilation of bottom borehole temperatures and geothermal gradients derived from new observations of bottom-simulating reflections (BSRs) allows us to constrain the relationship between the thermal regime and the known tectonic and sedimentary framework along this margin. Effects of basin and crustal structure on the estimation of thermal gradients and heat flow are discussed. A hydrate system is located within the sedimentary deep marine setting and compared to other provinces on other continental margins. We calculate the potential radiogenic contribution to the surface heat flow along a profile across the margin. Measurements across the continental shelf show intermediate thermal gradients of 38–44 °C/km. The onshore Indus Basin shows a lower range of values spanning 18–31 °C/km. The Indus Fan slope and continental rise show an increasing gradient from 37 to 55 °C/km, with higher values associated with the thick depocenter. The gradient drops to 33 °C/km along the Somnath Ridge, which is a syn-rift volcanic construct located in a landward position relative to the latest spreading center around the Cretaceous–Paleogene transition.  相似文献   

Establishment of modern circulation pattern at c. 6000 cal a BP in Disko Bugt,central West Greenland: opening of the Vaigat Strait     

KERSTIN PERNER  MATTHIAS MOROS  IAN SNOWBALL  JEREMY M. LLOYD  ANTOON KUIJPERS  THOMAS RICHTER 《第四纪科学杂志》2013,28(5):480-489

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