Application of Borehole Core Magnetic Susceptibility and PXRF Measurement to the Moon Mountain Copper-Iron Mining Area in Chile and Prospecting Prediction   总被引：1，自引：0，他引：1  

《地质与勘探》2012,48(2)

以智利月亮山铁氧化物铜金型矿床为例,利用磁化率K对铁磁性矿物及蚀变岩的现场识别能力和X射线荧光分析仪（PXRF）快速分析元素含量功能,结合矿床地质以闪长岩（5．5×10-3SI〈K〈17．9×10-3SI）、角砾岩（0．35×10-3SI〈K〈0．7×10-3SI）、磁铁矿（K〉753．4×10-3SI）、磁赤铁矿（313．3×10-3SI〈K〈753．4×10-3SI）、赤铁矿（0．78×10-3SI〈K〈1．62×10-3S1）、镜铁矿（0．67×10-3SI〈K〈0．78×10-3SI）等划分闪长岩亚相、角砾岩亚相、磁铁矿微相、磁赤铁矿微相、赤铁矿微相、镜铁矿微相;以PXRF现场测量铁含量〉30％,铜含量〉0．5％为含矿（化）界限,确定磁化率-铁铜含量对应关系：高磁化率-高铁含量-磁铁矿型、低磁化率-高铁含量-赤铁矿型（镜铁矿）、低磁化率-低铁含量-蚀变岩型,及岩相学找矿标志-矿物标志、构造标志、闪长岩标志、蚀变分带标志和矿物蚀变标志等,对月亮山矿区进行深部找矿预测。  相似文献   

The Mid-Carboniferous to Lowermost Permian succession of Spiti (Po Group and Ganmachidam Formation; Tethys Himalaya,Northern India): Gondwana glaciation and rifting of Neo-Tethys.     

Eduardo Garzanti  Lucia Angiolini  Dario Sciunnach 《Geodinamica Acta》2013,26(2-3):78-100

Abstract

The upper Lower Carboniferous to lowermost Permian terrigenous succession of the Spiti Valley can be subdivided into five formations (Thabo Formation, Fenestella Shale, Kabjima Quartzarenite, Chichong Formation and Ganmachidam Diamictite), here described in detail and subdivided into members or lithozones.

The Po Group, overlying the platform carbonates and gypsum deposits of the Lipak Formation, records an increase of subarkosic to quartzarenitic terrigenous detritus derived from uplift and erosion of continental blocks in the south during the initial stage of Neo-Tethyan rifting. Increasing mineralogic stability through the Thabo Formation broadly coincides with a climate change from tropical arid to temperate humid conditions during the Visean-Serpukhovian. The Fenestella Shale, containing rich brachiopod associations of Bashkirian age, documents a stage of widespread subsidence and transgression, followed by the regressive Kabjima Quartzarenite, which records recycling of quartzose sedimentary sequences in the south.

The Chichong Formation marks another transgressive event, associated with a significant increase of granitoid detritus, partly from nearby Lesser to High Himalayan source areas. Chaetetid, cephalopod and brachiopod faunas hint at a Moscovian age for the “Chaetetid beds”, at the top of which varve-like lamination and scattered pebbles suggest glacially influenced deposition. The overlying glacio-fluvial (?) cobble conglomerates (“Pebbly beds”) reflect onset of rapid tectonic uplift.

Abundant detritus from sedimentary rocks characterizes the overlying Ganmachidam Diamictite, deposited in glacio-marine environments; cold-water marine faunas of Asselian age occur in its middle part. Erosion of progressively older pre-rift sedimentary successions is ascribed to basin inversion, associated with unroofing of anatectic granitoids of the Lesser and High Himalayas. Basaltic to rhyolitic volcanic detritus documents alkalic magmatism at the climax of continental rifting.  相似文献   

长白山天池火山天文峰黄色浮岩的岩相学与显微结构特征   总被引：1，自引：0，他引：1  

许建东  于红梅  赵波 《地震地质》2013,35(2)

在长白山天池火口天文峰内壁发育数十m厚的爆炸式喷发堆积物,颜色各异.其中1套规模较大的黄色中弱熔结的粗粒浮岩空降堆积,堆积物碎屑粒径大,气孔大量发育,含有大粒径粗面岩岩块.文中对采于该套黄色堆积物的样品进行了全岩成分和显微结构特征分析,并与“千年大喷发”的空降浮岩进行了对比.研究结果表明:1)黄色浮岩与千年喷发的浮岩一样,属于碱性流纹岩,比千年喷发的灰白色浮岩略偏基性,可能由同一岩浆演化而来;2)黄色浮岩呈泡沫状,由不同大小的气孔、气孔壁和少量斑晶组成,部分较大的圆形气孔沿斑晶周围发育,呈串珠状排列,流动特征明显,黄色浮岩的斑晶类型和气孔结构与千年喷发的灰白色浮岩类似;3)已有扫描电镜和X射线衍射分析结果显示黄色浮岩中的长石参数与其他浮岩明显不同,可能是独立火山喷发事件的产物.上述岩石学证据表明,该套黄色堆积物是火山爆炸式喷发作用形成的浮岩空降堆积.  相似文献   

Sequence stratigraphic interpretation of a Pennsylvanian (Upper Carboniferous) coal from the central Appalachian Basin,USA     

RHODRI M. JERRETT  STEPHEN S. FLINT  ROY C. DAVIES  DAVID M. HODGSON 《Sedimentology》2011,58(5):1180-1207

Peat mires retain a sensitive record of water‐table (base‐level) fluctuations throughout their accumulation. On this basis, coals provide one of the best opportunities to interpret high‐resolution base‐level change in ancient non‐marine deposits. The petrographic composition of 275 samples collected from 11 localities along a 100 km south‐west to north‐east transect across the regionally extensive (>37 000 km²) Pennsylvanian (Upper Carboniferous) Fire Clay coal of the Central Appalachian Basin, USA was analysed to determine its internal stratigraphy. The coal is positioned within the late lowstand/early transgressive systems tract of a fourth‐order depositional sequence. The results of the petrographic analyses reveal a cyclicity in the composition of the Fire Clay coal, which defines six units that are correlated over more than 100 km. Each coal cycle is characterized by a gradual upward transition from vitrinite‐dominated to inertinite‐dominated coal, which represents a ‘drying‐up’ succession. Increased concentrations of resistant peat components at the top of the drying‐up successions indicate reduced peat accumulation rates associated with slowing rate of water‐table rise, and may represent a residue of peat remaining from a phase of exposure and erosion resulting from a falling water table. These drying‐up successions are bound by surfaces that display an abrupt coal facies shift from inertinite‐rich to vitrinite‐rich coal, representing a rapid water‐table rise. Each cycle represents markedly different mire conditions with different aerial distributions, which supports the notion of temporal disconnection between each unit of coal, and suggests that considerable time may be ‘locked‐up’ in unit bounding exposure surfaces. Recognition that the rate of peat accumulation in a mire may vary considerably through time, has important implications for studies which assume that peat and coal successions provide continuous and time‐invariant records of base‐level fluctuations or palaeoecological change.  相似文献   

Crystal Size Distributions Derived from 3D Datasets: Sample Size Versus Uncertainties   总被引：4，自引：1，他引：3  

GUALDA  GUILHERME A. R. 《Journal of Petrology》2006,47(6):1245-1254

Crystal size distributions (CSD) are the most commonly studiedcharacter in quantitative textural investigations of igneousrocks. The quality of CSD depends fundamentally on the samplesize (i.e. total number of crystals). Here we use 3D X-ray tomographicdatasets of two early erupted Bishop Tuff pumice clasts (comprising849 and 446 quartz crystals) to investigate the effect of samplesize on the quality of the quartz size distributions. BecauseCSD are obtained using a counting procedure, uncertainties relatedto counting statistics can be used as minimum estimates of error.Given that most natural samples are characterized by a decreasingnumber of crystals with increasing crystal size, uncertaintiestend to increase markedly with crystal size, and the numberof small crystals to be counted grows very quickly with increasingsample size. Accordingly, with as few as 100 crystals in total,it is possible to properly estimate the population densitiesfor small size bins (20–80 µm). However, to obtainmeaningful estimates across four bin sizes (20–320 µm),at least 250 crystals, but preferably >400 crystals are needed.To minimize the total number of crystals counted, and keep theuncertainties on the larger size ranges within reasonable values,it becomes necessary to study multiple volumes at variable spatialresolution. KEY WORDS: crystal size distributions; quantitative petrography; texture; X-ray tomography  相似文献   

新疆西准噶尔夏尔莆岩体岩浆混合的岩相学证据   总被引：11，自引：0，他引：11  

康磊  李永军  张兵  张洪伟  王军年 《岩石矿物学杂志》2009,28(5):423-432

夏尔莆岩体由寄主岩石、微粒镁铁质包体和中基性岩墙群组成,具丰富、典型的岩浆混合岩相学特征.野外露头,寄主岩石中暗色矿物分布不均并发育暗色矿物集合体、微小的镁铁质包体和不均匀混合条带;包体具有明显的塑性变形,与寄主岩石或界线截然或渐变过渡,常发育反向脉和寄主岩石中的长石巨晶(捕虏晶);中基性岩墙群与微粒镁铁质包体紧密共生并延伸方向基本一致,发育寄主岩石中的长石捕虏晶,被寄主岩的反向脉横切.在镜下,包体与寄主岩混合带中均发育斜长石异常环带和多种不平衡矿物共生现象,包体中发育针状磷灰石.这些特征表明镁铁质包体和中基性岩墙群来源于与寄主岩石同一岩浆事件的基性岩浆,并与其发生了强烈的岩浆混合作用.岩相学特征为夏尔莆岩体岩浆混合成因提供了重要佐证.  相似文献   

3D quantification of mineral components and porosity distribution in Westphalian C sandstone by microfocus X-ray computed tomography     

Haili Long  Rudy Swennen  Anneleen Foubert  Manuel Dierick  Patric Jacobs 《Sedimentary Geology》2009,220(1-2):116-125

Microfocus X-ray computed tomography (µCT) measurements were performed on deltaic sandstone samples from the diagenetically altered Westphalian C strata (Campine basin, north-east Belgium) in order to collect three dimensional data on mineral (quartz, kaolinite, ankerite, etc.) and porosity distribution. The acquired µCT data were compared with point counting results of stained impregnated thin-sections to qualify the sensitivity of µCT. Comparison between techniques shows positive results with regard to the quantification of main mineral phases such as quartz and ankerite, and porosity distribution. However, major discrepancies exist when studying the clay minerals. This can be explained by the influence of microporosity associated with these clay minerals, resulting in partial volume effects.  相似文献   

浙江花岗岩的工程岩石学研究     

MoustafaElOmella C.A.Tang T.Xu 《地质与资源》2005,14(3):176-180

对浙江省花岗岩的岩相学特征及力学性质进行了研究以确定它们之间的关系.矿物学研究显示出花岗岩的交代蚀变特征,这可以反映在岩石的力学性质上.岩石材料的物理性质决定其工程学性质,在相关定量参数确定的情况下,可以预测岩石材料的工程学性质.镜下观察、硬度、密度、孔隙度及点负荷强度均可作为所研究花岗岩的定量参数.上述每个因素都可提供岩石工程学的可靠预测.岩石的物理性质受岩石成分及蚀变状态控制,而岩石的工程学性质和力学特征是其物理性质的函数.  相似文献   

Carbonate stromatolites from a Messinian hypersaline setting in the Caltanissetta Basin, Sicily: petrographic evidence of microbial activity and related stable isotope and rare earth element signatures     

ELVIRA OLIVERI  RODOLFO NERI  ADRIANA BELLANCA  ROBERT RIDING†  Associate Editor: Tracy Frank 《Sedimentology》2010,57(1):142-161

Lower Messinian stromatolites of the Calcare di Base Formation at Sutera in Sicily record periods of low sea‐level, strong evaporation and elevated salinity, thought to be associated with the onset of the Messinian Salinity Crisis. Overlying aragonitic limestones were precipitated in normal to slightly evaporative conditions, occasionally influenced by an influx of meteoric water. Evidence of bacterial involvement in carbonate formation is recorded in three dolomite‐rich stromatolite beds in the lower portion of the section that contain low domes with irregular crinkly millimetre‐scale lamination and small fenestrae. The dominant microfabrics are: (i) peloidal and clotted dolomicrite with calcite‐filled fenestrae; (ii) dolomicrite with bacterium‐like filaments and pores partially filled by calcite or black amorphous matter; and (iii) micrite in which fenestrae alternate with dark thin wispy micrite. The filaments resemble Beggiatoa‐like sulphur bacteria. Under scanning electron microscopy, the filaments consist of spherical aggregates of dolomite, interpreted to result from calcification of bacterial microcolonies. The dolomite crystals are commonly arranged as rounded grains that appear to be incorporated or absorbed into developing crystal faces. Biofilm‐like remains occur in voids between the filaments. The dolomite consistently shows negative δ¹³C values (down to ?11·3‰) and very positive δ¹⁸O (mean value 7·9‰) that suggest formation as primary precipitate with a substantial contribution of organic CO₂. Very negative δ¹³C values (down to ?31·6‰) of early diagenetic calcite associated with the dolomite suggest contribution of CO₂ originating by anaerobic methane oxidation. The shale‐normalized rare earth element patterns of Sutera stromatolites show features similar to those in present‐day microbial mats with enrichment in light rare earth elements, and M‐type tetrad effects (enrichment around Pr coupled to a decline around Nd and a peak around Sm and Eu). Taken together, the petrography and geochemistry of the Sutera stromatolites provide diverse and compelling evidence for microbial influence on carbonate precipitation.  相似文献   

甘肃高台-临泽地区109-2隐伏岩体岩石地球化学特征   总被引：1，自引：0，他引：1  

焦建刚  汤中立  闫海卿  刘瑞平 《大地构造与成矿学》2007,31(2):218-225

对高台-临泽地区109-2隐伏岩体岩相学研究,岩体组成以二辉橄榄岩相为主,具有橄榄石堆晶结构,橄榄石主要为贵橄榄石,阳起石化、绿泥石化、碳酸岩化与金川岩体非常相似。与金川地质背景对比显示它们属于同一个三级构造单元(龙首山隆起带),围岩地层相近。微量、稀土数据证明金川岩体岩浆源区富集程度或受地壳混染程度较109-2岩体强,分异结晶过程存在差异,109-2岩体Cr有明显的亏损现象,Ni/Cu比值明显较金川超镁铁质岩体(Ni/Cu≈2)高。109-2岩体所在地区可能是一个新的岩浆能量聚集地带,值得进一步探矿工作。  相似文献