Petrogenesis and tectonic significance of Jurassic IAT magma types in the Hellenide ophiolites as deduced from the Rhodiani ophiolites (Pelagonian zone, Greece)   总被引：1，自引：0，他引：1  

Emilio Saccani  Adonis Photiades  Luigi Beccaluva   《Lithos》2008,104(1-4):71-84

The Rhodiani ophiolites are represented by two tectonically superimposed ophiolitic units: the “lower” Ultramafic unit and the “upper” Volcanic unit, both bearing calcareous sedimentary covers. The Ultramafic unit consists of mantle harzburgites with dunite pods and chromitite ores, and represents the typical mantle section of supra-subduction zone (SSZ) settings. The Volcanic unit is represented by a sheeted dyke complex overlain by a pillow and massive lava sequence, both including basalts, basaltic andesites, andesites, and dacites. Chemically, the Volcanic unit displays low-Ti affinity typical of island arc tholeiite (IAT) ophiolitic series from SSZ settings, having, as most distinctive chemical features, low Ti/V ratios (< 20) and depletion in high field strength elements and light rare earth elements.The rare earth element and incompatible element composition of the more primitive basaltic andesites from the Rhodiani ophiolites can be successfully reproduced with about 15% non-modal fractional melting of depleted lherzolites, which are very common in the Hellenide ophiolites. The calculated residua correspond to the depleted harzburgites found in the Rhodiani and Othrys ophiolites. Both field and chemical evidence suggest that the whole sequence of the Rhodiani Volcanic unit (from basalt to dacite) originated by low-pressure fractional crystallization under partially open-system conditions. The modelling of mantle source, melt generation, and mantle residua carried out in this paper provides new constraints for the tectono-magmatic evolution of the Mirdita–Pindos oceanic basin.  相似文献   

Detailed <Superscript>40</Superscript>Ar/<Superscript>39</Superscript>Ar dating of geologic events associated with the Mantos Blancos copper deposit,northern Chile     

Verónica Oliveros  Gilbert Féraud  Luis Aguirre  Luis Ramírez  Michel Fornari  Carlos Palacios  Miguel Parada 《Mineralium Deposita》2008,43(3):281-293

The ⁴⁰Ar/³⁹Ar geochronological method was applied to date magmatic and hydrothermal alteration events in the Mantos Blancos mining district in the Coastal Cordillera of northern Chile, allowing the distinction of two separate mineralization events. The Late Jurassic Mantos Blancos orebody, hosted in Jurassic volcanic rocks, is a magmatic-hydrothermal breccia-style Cu deposit. Two superimposed mineralization events have been recently proposed. The first event is accompanied by a phyllic hydrothermal alteration affecting a rhyolitic dome. The second mineralization event is related to the intrusion of bimodal stocks and sills inside the deposit. Because of the superposition of several magmatic and hydrothermal events, the obtained ⁴⁰Ar/³⁹Ar age data are complex; however, with a careful interpretation of the age spectra, it is possible to detect complex histories of successive emplacement, alteration, mineralization, and thermal resetting. The extrusion of Jurassic basic to intermediate volcanic rocks of the La Negra Formation is dated at 156.3 ± 1.4 Ma (2σ) using plagioclase from an andesitic lava flow. The first mineralization event and associated phyllic alteration affecting the rhyolitic dome occurred around 155–156 Ma. A younger bimodal intrusive event, supposed to be equivalent to the bimodal stock and sill system inside the deposit, is probably responsible for the second mineralization event dated at ca. 142 Ma. Other low-temperature alteration events have been dated on sericitized plagioclase at ca. 145–146, 125, and 101 Ma. This is the first time that two distinct mineralization events have been documented from radiometric data for a copper deposit in the metallogenic belt of the Coastal Cordillera of northern Chile. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

“Cretaceous black flysch” in the Pieniny Klippen Belt, West Carpathians: a case of geological misinterpretation     

Krzysztof Birkenmajer  Przemys&#x;aw Gedl  Ryszard Myczy&#x;ski  Jaros&#x;aw Tyszka 《Cretaceous Research》2008,29(3):535-549

This is a critical assessment of the paper by Oszczypko et al. (2004: Cretaceous Research 25, 89–113), in which they tried to prove a mid-Cretaceous age for the Szlachtowa (“black flysch”) and Opaleniec Formations, in the Pieniny Klippen Belt, West Carpathians, both of which had previously been shown to be of Jurassic age. We argue that the mid-Cretaceous age assignment is a misinterpretation, primarily resulting from their field samples having been collected from some Cretaceous lithostratigraphic units, tectonically associated with the Jurassic formations, and/or from tectonic contact-breccias involving Jurassic and Cretaceous strata. In addition, we suggest that they have overlooked a number of significant palaeontological papers, published since 1962, which record the presence of in situ ammonites, aptychi, belemnites, thin-shelled bivalves (Bositra), gryphaeids, foraminifera, and ostracod assemblages, all indicating a Jurassic (mainly Aalenian), and not a Cretaceous, age for the Szlachtowa Formation, and also the in situ Jurassic (Bajocian) ammonites and thin-shelled bivalves (Bositra), Bositra-microfacies, and age-diagnostic foraminiferal assemblages of the Opaleniec Formation.Our presentation here of recently published dinocyst data from well-preserved assemblages further supports the Jurassic ages for the Szlachtowa (“black flysch”) and Opaleniec Formations.  相似文献   

藏北南羌塘盆地毕洛错地区下侏罗统曲色组石膏岩层   总被引：1，自引：0，他引：1  

王永胜  郑春子 《地层学杂志》2008,32(3)

对西藏自治区北部南羌塘盆地毕洛错地区下侏罗统曲色组石膏岩层进行了研究。根据岩石地层和生物地层资料,确认毕洛错地区的石膏岩层和油页岩为曲色组的一部分,地质时代为早侏罗世,并确认下侏罗统曲色组在区域上可能是寻找油气、油页岩资源的重要层位之一。  相似文献   

鱼卡煤田大煤沟组高分辨率层序地层特征及聚煤规律   总被引：1，自引：0，他引：1  

白生海  田景春  肖玲  张翔 《地层学杂志》2008,32(4)

利用高分辨率层序地层学理论和技术方法,综合地震、测井、岩芯和煤质资料对柴达木盆地北缘鱼卡煤田中下侏罗统大煤沟组地层河湖三角洲沉积体系进行高分辨率层序地层学分析,从中识别出短期、中期、长期3个级别的基准面旋回层序,划分出向上"变深"非对称型、向上"变浅"非对称型及对称型3种短期基准面旋回基本结构类型。依据等时地层对比法则进行不同级次基准面旋回层序的联井对比,建立了大煤沟组的等时地层格架,在等时地层格架内进行了煤层对比,并在等时地层格架内分析了聚煤规律。  相似文献   

新疆境内塔拉斯 费尔干纳断裂早侏罗世走滑的古地震证据     

乔秀夫  李海兵  王思恩  郭宪璞  司家亮  宗文明 《地质学报》2008,82(6):722-730

在野外考察过程中,于新疆乌恰地区早侏罗世康苏组沼泽相砂岩层中,发现并识别出软沉积物液化变形层,变形包括负载构造,球枕构造及卷曲变形构造。通过模拟试验的对比研究认为,该软沉积物变形机制与液化作用有关,触发沉积物液化的动力是古地震,并且根据地震震级与液化最大震中距的关系,推测出造成早侏罗世软沉积物变形的里氏地震震级为6相似文献   

柴达木盆地北缘侏罗系不同沉积环境烃源岩生物标志物特征及其应用   总被引：2，自引：0，他引：2  

曹剑  边立曾  胡凯  刘云田  汪立群  杨少勇  陈琰 《地质学报》2008,82(8):1121-1128

柴达木盆地北缘地区侏罗系(中下侏罗统)的优质烃源岩主要发育于湖相与三角洲相环境。研究了不同时代、不同沉积环境中烃源岩的生物标志物组成特征,结果发现,有3类化合物的分布与组成差异显著,包括三环萜烷(C19、C20、C21)的分布型式、重排藿烷的丰度以及规则甾烷的相对组成。其中,不同时代的差异主要体现在规则甾烷组成上;而不同沉积环境的差异主要体现为三环萜烷(C19、C20、C21)的分布型式及重排藿烷的丰度。分析认为,这些差异与烃源岩的沉积环境及其生源组成有密切关系。据此,初步将这些参数应用于两方面研究,一是为划分地层沉积环境提供“生物标志物相标志”,二是研究油源对比,取得良好效果。因此,本文研究结果具有重要实用价值与参考意义。  相似文献   

新疆境内塔拉斯-费尔干纳断裂早侏罗世走滑的古地震证据   总被引：11，自引：2，他引：9  

乔秀夫  李海兵  王思恩  郭宪璞  司家亮  宗文明 《地质学报》2008,82(6)

在野外考察过程中,于新疆乌恰地区早侏罗世康苏组沼泽相砂岩层中,发现并识别出软沉积物液化变形层,变形包括负载构造,球-枕构造及卷曲变形构造。通过模拟试验的对比研究认为,该软沉积物变形机制与液化作用有关,触发沉积物液化的动力是古地震,并且根据地震震级与液化最大震中距的关系,推测出造成早侏罗世软沉积物变形的里氏地震震级为6相似文献   

The quest for refined calibration of the Jurassic time-scale     

József Pálfy 《Proceedings of the Geologists' Association. Geologists' Association》2008,119(1):85-95

  相似文献   

Drawing the line: the history of the Jurassic—Cretaceous boundary     

John C.W. Cope 《Proceedings of the Geologists' Association. Geologists' Association》2008,119(1):105-117

  相似文献