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1.
Volcanism along the northwest boundary of the Arabian Plate found in the Gaziantep Basin, southeast Turkey, is of Miocene age and is of alkaline and calc-alkaline basic composition. The rare earth element data for both compositional series indicates spinel–peridotite source areas. The rare earth and trace elements of the alkaline lavas originate from a highly primitive and slightly contaminated asthenospheric mantle; those of the calc-alkaline lavas originate from a highly heterogeneous, asthenospheric, and lithospheric mantle source. Partial melting and magmatic differentiation processes played a role in the formation of the petrological features of these volcanics. These rocks form two groups on the basis of their ~(87) Sr/~(86) Sr and ~(143) Nd/~(144) Nd isotopic compositions in addition to their classifications based on their chemical compositions(alkaline and calc-alkaline). These isotopic differences indicate a dissimilar parental magma. Therefore, high Nd isotope samples imply a previously formed and highly primitive mantle whereas low Nd isotope samples may indicate comparable partial melting of an enriched heterogeneous shallow mantle. Other isotopic changes that do not conform to the chemical features of these lavas are partly related to the various tectonic events of the region, such as the Dead Sea Fault System and the Bitlis Suture Zone.  相似文献   
2.
激光钻进技术是一种极具潜力的创新技术,也是钻探领域的研究热点。作为一种非接触式钻进技术,对破碎松软岩层扰动破坏小,将激光钻进应用于煤层气定向钻进中可发挥出非常明显的优势。梳理和总结了激光用于煤岩钻进的成孔机制、钻进效果的影响因素。在激光钻进过程中,激光与煤岩相互作用伴随着复杂的理化作用,指出激光钻进煤岩主要的成孔机制是烧蚀成孔。从激光参数、岩石性质、外部环境等方面阐述了影响激光钻进煤岩效果的因素,论述了激光钻进用于煤岩这一特定钻进对象的特殊现象和问题,指出煤岩在激光照射下,组分的挥发、热解、升华、烧结和氧化构成了煤岩在高温下主要的热烧蚀机制。从钻进机理、工艺、装置等方面着手,建议加强激光钻进煤岩的多物理场耦合作用机制、钻进工艺、钻进装置研制等适应性研究,为激光用于煤岩的高质高效钻进研究提供参考。   相似文献   
3.
塔里木盆地东南缘下—中侏罗统煤层沿阿尔金山前断续分布,其煤岩、煤质与典型的西北侏罗纪煤层具有明显不同。通过对和田布雅、于田普鲁、且末红柳沟等煤矿主采煤层样品进行煤岩、煤质鉴定及煤化指标等一系列综合研究分析,结果表明,主采煤层以光亮煤、半亮煤为主,其次是半暗煤、暗淡煤;煤岩组分以镜质组为主,壳质组含量少,具中-高镜惰比。因成煤沼泽的还原程度促进了无机硫分的形成,煤中全硫含量随镜质组含量的增加呈现逐渐增高的趋势,且煤层硫分与灰分整体具有明显的负相关关系。此外,煤层挥发分受不同种类硫分的影响,亦有明显差异性变化。在民丰凹陷中-高硫煤中,硫分以无机硫为主,随着硫分的升高挥发分亦有升高趋势;瓦石峡凹陷中-低硫煤受有机硫控制,对挥发分产率的影响不明显。民丰凹陷煤层的灰分指数高于瓦石峡凹陷,可见后者的成煤沼泽环境潜水面要比前者高得多。针对上述诸多因素分析,进一步揭示塔东南地区煤岩、煤质多样性变化受断陷湖盆以及局部水体较深的还原型沼泽环境控制,最终形成了中-高挥发分、中-低灰分、中-低硫分的煤质及富镜贫惰的煤岩特征。  相似文献   
4.
花山锑金矿床位于皖南东至县境内, 是皖南地区代表性金-多金属矿床之一。 本次工作对花山锑金矿床开展了野外地质、岩相学特征观察以及金属硫化物电子探针分析, 得到以下结论:1) 花山锑金矿床主要成矿阶段可分为毒砂-黄铁矿(PyⅠ)阶段、黄铜矿-黄铁矿 (PyⅡ)阶段和方解石-辉锑矿阶段。 2) 金在不同阶段硫化物中均有赋存, 其矿化伴随整个热液成矿过程, 且以毒砂-PyⅠ阶段和黄铜矿-PyⅡ阶段为主。 毒砂-PyⅠ阶段和黄铜矿-PyⅡ阶段发育金矿化, 无锑矿化, 方解石-辉锑矿阶段发育锑、金共生矿化。 3) 早阶段即毒砂 -PyⅠ阶段和黄铜矿-PyⅡ阶段载金矿物为黄铁矿、毒砂及黄铜矿, 成矿物质来源以地层为 主;晚阶段即方解石-辉锑矿阶段载金矿物为辉锑矿, 成矿物质来源以燕山期岩浆岩为主。 本次工作对东至及皖南地区金矿床的寻找勘探具有重要的指示意义。  相似文献   
5.
沈立军 《地质与勘探》2014,50(2):321-331
本文以智博铁矿区内的安山岩为研究对象,通过详细的野外地质调查,并利用电子显微镜和电子探针,对安山岩中的主要矿物进行了系统的岩相学观察和矿物学研究。研究表明,智博安山岩中斜长石主要为Na-高钠长石,具低TiO2,高Na2O和Al2O3的特点;辉石主要为普通辉石,具高TiO2,高Al2O3的特点;角闪石主要为镁角闪石和阳起石,具低TiO2和Al2O3,高MgO的特点;副矿物磁铁矿具高TiO2,低MgO和Al2O3的特点。辉石、角闪石矿物化学特征表明,智博铁矿安山岩的母岩浆属于壳幔混源的玄武质岩浆,构造环境为火山岛弧环境。智博安山岩中单斜辉石结晶温度为1225℃左右,结晶压力约0.795GPa,结晶深度约26km。智博铁矿后期的热液作用也参与了磁铁矿成矿,对智博铁矿的成矿有一定的贡献。  相似文献   
6.
Four sample sets of the Upper and Middle Loire river sands were analyzed in order to study the impact of natural and anthropogenic factors on their petrographic composition in space (on an 800 km stretch) and time. Composition was determined by modal analysis of three sand-size fractions using a polarizing optical microscope and calculated for each sample (“standard sand” = Sst). The watershed is composed mainly of endogenic (Massif Central) and sedimentary (southern Parisian Basin) rocks. B-set sands collected in channels for different water flows in 1996 show that Sst compositions vary by only 5 %. Present-day sands in the Upper Loire and Middle Loire have very high petrographic immaturity comparing to others worldwide fluvial sands, although bio-climatic conditions favor sand maturation by source-rock weathering in the watershed. This shows the strong impact of the Massif Central on sediment yield due to relief rejuvenation as a consequence of the formation of the Alps during the Quaternary. Fluvial sands stored during the Weichselian and the Holocene in the Middle Loire floodplain, although partly weathered since their deposition, show higher inputs from the endogenic rocks of the Massif Central than present-day deposits. This can be explained by Weichselian periglacial conditions and the development of crop farming since the Neolithic, which favored mechanical erosion, particularly in the Massif Central which is characterized by a cold, humid climate and steep slopes. The upstream-downstream change in the composition of presently deposited sand is low in the diked area. It shows however that basalt and some heavy mineral grains are vulnerable to abrasion during transport and indicates a marked sediment yield from ancient sediment stored in the floodplain. This is in line with the high incision of the river bed over the last 150 years partly due to dam construction and aggregate mining.  相似文献   
7.
Abstract

This work deals with the Cretaceous-Tertiary Helminthoid flysch successions of the Emilian Apennines and related basal complexes (Mt. Caio, Val Baganza, Solignano, Mt. Venere-Monghidoro and Mt. Cassio Units): it is based on an integrated approach which included stratigraphic, petrographic and structural observations. Detailed stratigraphic sections measured in the various successions evidenced the specific features of the different flysch formations. The main framework composition analysis of the arenites pointed out a partly ‘oceanic’ alimentation for the Mt. Caio Flysch Fm; the Mt. Venere-Monghidoro, and Mt. Cassio Flysch Fms have been alimented exclusively by a terrigenous detritus mainly derived from continental basement source areas. The heavy mineral assemblage of the Mt. Caio Flysch Fm is characterized by picotite, that of the Mt. Venere-Monghidoro, Solignano and Mt. Cassio Flysch Fms commonly contains straurolite, garnet and chloritoid, generally considered to be typical products of the Adriatic continental margin. The calcareous nannofossils biostratigraphy indicated that the flysch sedimentation started during the Late Campanian and ended between the Paleocene (Mt. Cassio Flysch Fm and Mt. Venere-Monghidoro Fms) and the Middle Eocene (Mt. Caio Flysch Fm). We propose a schematic paleogeographic restoration for the External Ligurian Domain which implies a more internal position for the Mt. Caio succession and a more external one for the Mt. Venere-Monghidoro and Mt. Cassio successions. The Helminthoid flyschs sedimented after and during deformation and subduction phases in perched and fore-arc basins partly overlying the marginal part of the Adriatic plate. The External Ligurian nappes’ stacking consists, in the study area, from the bottom, of the following units: Caio Unit, Val Baganza Ophiolitic Unit, Monghidoro Unit, Cassio Unit. This pile of thrust-nappes, sealed by the Epiligurian succession, has been already realized before Late Eocene. In our opinion it was generated by a frontal west-verging frontal accretion process (offscraping), which let the flysch successions remain, in this phase, quite undeformed. This westverging thrusting phase, starting from the Middle-Late Eocene, has been followed by an important folding event which generated striking hectometric and kilometric ‘Apenninic’ reverse folds, sometimes associated with NE-verging thrust surfaces. The Oligocene and post-Oligocene evolution is characterized by a block-translation of the Ligurian staking over the Subligurian, Tuscan and Umbrian Domains, associated with a new generation of minor thrusts and thrust related Apenninic folds. © 2000 Éditions scientifiques et médicales Elsevier SAS  相似文献   
8.
新疆图拉尔根Ni-Cu硫化物矿床产于康古儿塔格—黄山韧性剪切带的北东段,属于岩浆熔离贯入型矿床。1号岩体以全岩矿化为特征,各岩相环带状产出,岩性具有单期岩浆多次脉动上涌成矿特征。由大地电磁测深剖面图、稀土元素配分曲线和微量元素可知1号和2号岩体具有同源性,并具有互补性,在深部具有同一个岩浆通道。较低的La/Sm(2)和Th/Ta值(4.6)表明成矿岩浆为地幔来源,岩体就位时很少受到地壳的混染。PGE特征表明,图拉尔根岩浆源于地幔低程度的部分熔融。Pd-Ni图显示在岩浆演化早期没有发生过硫化物的熔离作用。根据岩石学、岩相学、地球化学等资料综合分析,对图拉尔根Ni-Cu硫化物矿床的成矿模式进行了探讨,认为其成矿模式为深部熔离反相复式贯入成矿。构造在图拉尔根矿床就位过程中起了重要影响,决定了矿体的产出状态。  相似文献   
9.
《International Geology Review》2012,54(13):1508-1521
Twenty Cretaceous shale samples from two wells in the Orange Basin of South Africa were evaluated for their source rock potential. They were sampled from within a 1400 m-thick sequence in boreholes drilled through Lower to Upper Cretaceous sediments. The samples exhibit total organic carbon (TOC) content of 1.06–2.17%; Rock-Eval S2 values of 0.08–2.27 mg HC/g; and petroleum source potential (SP), which is the sum of S1 and S2, of 0.10–2.61 mg HC/g, all indicating the presence of poor to fair hydrocarbon generative potential. Hydrogen index (HI) values vary from 7 to 128 mg HC/g organic carbon and oxygen index (OI) ranges from 37 to 195 mg CO2/g organic carbon, indicating predominantly Type III kerogen with perhaps minor amounts of Type IV kerogen. The maturity of the samples, as indicated by T max values of 428–446°C, ranges from immature to thermally mature with respect to oil generation. Measured vitrinite reflectance values (%Ro) of representative samples indicate that these samples vary from immature to mature, consistent with the thermal alteration index (TAI) (spore colour) and fluorescence data for these samples. Organic petrographic analysis also shows that amorphous organic matter is dominant in these samples. Framboidal pyrite is abundant and may be indicative of a marine influence during deposition. Although our Rock-Eval pyrolysis data indicate that gas-prone source rocks are prevalent in this part of the Orange Basin, the geochemical characteristics of samples from an Aptian unit at 3318 m in one of the wells suggest that better quality source rocks may exist deeper, in more distal depositional parts of the basin.  相似文献   
10.
For the Quaternary and Neogene, aragonitic biogenic and abiogenic carbonates are frequently exploited as archives of their environment. Conversely, pre‐Neogene aragonite is often diagenetically altered and calcite archives are studied instead. Nevertheless, the exact sequence of diagenetic processes and products is difficult to disclose from naturally altered material. Here, experiments were performed to understand biogenic aragonite alteration processes and products. Shell subsamples of the bivalve Arctica islandica were exposed to hydrothermal alteration. Thermal boundary conditions were set at 100°C, 175°C and 200°C. These comparably high temperatures were chosen to shorten experimental durations. Subsamples were exposed to different 18O‐depleted fluids for durations between two and twenty weeks. Alteration was documented using X‐ray diffraction, cathodoluminescence, fluorescence and scanning electron microscopy, as well as conventional and clumped isotope analyses. Experiments performed at 100°C show redistribution and darkening of organic matter, but lack evidence for diagenetic alteration, except in Δ47 which show the effects of annealing processes. At 175°C, valves undergo significant aragonite to calcite transformation and neomorphism. The δ18O signature supports transformation via dissolution and reprecipitation, but isotopic exchange is limited by fluid migration through the subsamples. Individual growth increments in these subsamples exhibit bright orange luminescence. At 200°C, valves are fully transformed to calcite and exhibit purple‐blue luminescence with orange bands. The δ18O and Δ47 signatures reveal exchange with the aqueous fluid, whereas δ13C remains unaltered in all experiments, indicating a carbonate‐buffered system. Clumped isotope temperatures in high‐temperature experiments show compositions in broad agreement with the measured temperature. Experimentally induced alteration patterns are comparable with individual features present in Pleistocene shells. This study represents a significant step towards sequential analysis of diagenetic features in biogenic aragonites and sheds light on reaction times and threshold limits. The limitations of a study restricted to a single test organism are acknowledged and call for refined follow‐up experiments.  相似文献   
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