烟台市牟平区宋家沟金矿床成因及找矿方向

宋家沟金矿产于早白垩世莱阳群砾岩中 ,为受断裂、裂隙密集带控制的蚀变砾岩型金矿床。该金矿床为一隐伏矿床 ,与产于盆缘的蓬家夼蚀变岩型金矿的成矿条件相似 ,控矿的主导因素为断裂构造 ,成矿时代为中生代燕山晚期。     

Clasts of Variscan high-grade rocks within Upper Viséan conglomerates – constraints on exhumation history from petrology and U-Pb chronology

In this paper, U‐Pb zircon, monazite and rutile data for crystalline rocks deposited as clasts in the Upper Viséan conglomerates at the eastern margin of the Bohemian Massif are reported. U‐Pb data of spherical zircon from three different granulite clasts yielded a mean age of 339.0 ± 0.7 Ma (±2σ), while oval and spherical grains of another granulite pebble define a slightly younger date of 337.1 ± 1.1 Ma. These ages are interpreted as dating granulite facies metamorphism. Thermochronology and the derived pressure–temperature (P–T) path of the granulite pebbles reflect two‐stage exhumation of the granulites. Near‐to‐isothermal decompression from at least 44 km to mid‐crustal depths of around 22 km was followed by a near‐isobaric cooling stage based on reaction textures and geothermobarometry. Minimum average exhumation rate corresponds to 2.8–4.3 mm year^?1. The extensive medium‐pressure/high‐temperature overprint on granulite assemblages is dated by U‐Pb in monazite at c. 333 Ma. This thermal event probably has a close link to generation and emplacement of voluminous Moldanubian granites, including the cordierite granite present in clasts. This granite was emplaced at mid‐crustal levels at 331 ± 3 Ma (U‐Pb monazite), whereas the U‐Pb zircon ages record only a previous magmatic event at c. 378 Ma. Eclogites and garnet peridotites normally associated with high‐pressure granulites are absent in the clasts but exotic subvolcanic and volcanic members of the ultrapotassic igneous rock series (durbachites) of the Bohemian Massif have been found in the clasts. It is therefore assumed that the clasts deposited in the Upper Viséan conglomerates sampled a structurally higher tectonic unit than the one that corresponds to the present denudation level of the Moldanubicum of the Bohemian Massif. The strong medium‐temperature overprint on granulites dated at c. 333 Ma is attributed to the relatively small size of the entirely eroded bodies compared with the presently exposed granulites.     

论清源北部太古代地质几个基本问题

以岩石学与构造研究相结合为基础，宏观与微观观察为主，地球化学为辅的综合研究方法论证了本区太古代地质体由三套变质建造组成。其中花岗质岩石占７１％，原地深熔紫苏花岗岩为１１．８％，浅色麻粒岩是１．２％，浅粒岩、含砾麻粒岩质浅粒岩（底砾岩）３６．７％和原地深熔花岗岩２０％。高角闪岩相以浅位岩为主原地深熔花岗岩的原岩建造为类磨拉石建造系列，低角闪岩似绿岩建造的原岩建造为镁铁质泥灰岩粉砂岩型复理石建造。其地质体是由６１．２％的层状变质岩系和３１．８％的原地深熔花岗岩组成。根据各建造的地层缺生，底砾岩及低、高角闪岩相矿物共生组合区域性叠加和变辉绿岩群的分布规律，确定三套变质建造为不整合接触，据此提出新的划分方案并与华北地台北部太古界分布区作了对比，事实证明岩石地层学的方法，在太古代地质与成矿研究中仍是有效的。     

准噶尔盆地砾岩油藏水淹层的测井评价方法研究

基于对准噶尔盆地某砾岩油藏的淡水水淹机理的实验认识,考察了砾岩油藏水淹层的测井响应特征,形成了一套定性识别水淹层和划分水淹级别的方法.在该基础上,按照"岩心刻度测井"的原则,统计建立了一套适用于该砾岩油藏淡水水淹层的测井评价方法.该方法在7个区块17口井的测井解释结果表明,水淹级别按6级划分的解释符合率达85%左右.     

贺兰山北段晚三叠世沉积物源分析

贺兰山北段晚三叠世地层分布较广泛,其物源问题是进行鄂尔多斯盆地西北部原盆边界恢复和其两侧盆地该时期面貌恢复的关键,而对此存在一定的争议。该研究以贺兰山北段的沉积-构造背景为约束,通过晚三叠世地层的砾石成分、古流向、稀土元素、锆石测年及沉积趋势等物源分析方法综合运用,指出贺兰山北段晚三叠世不存在东部物源,银川古隆起不存在;物源来自西北部的阿拉善地块和兴蒙造山带太古代-古元古代的变质岩（片麻岩和变粒岩等）和岩浆岩,部分为阿拉善地块古生代和早中三叠世的沉积岩及岩浆岩。贺兰山西北部具有近物源和快速堆积的特点。同时,贺兰山北段晚三叠世物源具有多源性,其经历了多期的构造改造,恢复物源区演化模式对周邻造山带和块体的演化具有深远意义。     

青藏高原羌塘南部冰海杂砾岩的成因与物源——以冈玛错地区为例

青藏高原及其邻区石炭纪—二叠纪地层中广泛分布的漂砾层、杂砾岩、含砾板岩等是一套特殊的冰海相沉积岩,称为冰海杂砾岩,前人已对它的成因环境做了初步的研究,但没有获得统一的结论。本次以青藏高原羌塘南部冈玛错地区冰海杂砾岩的砾石为研究对象,观察它们的野外特征和镜下特点,并对与冰海杂砾岩互层产出的石英砂岩做了粒度分析。结果表明,冰海杂砾岩是在冈瓦纳大陆冰川呈消融状的情况下,冰阀搬运沉积的产物。通过碎屑锆石和岩性对比,初步认为冰海杂砾岩的物源为冈瓦纳大陆,并简单论述了冰海杂砾岩各类砾石的可能来源。以上研究成果为探讨冈瓦纳大陆的沉积环境提供了依据。     

Radioactive quartz-pebble conglomerates from western margin of Bonai granite pluton,Sundargarh district,Orissa — A new find

Several radioactive quartz-pebble conglomerate (QPC) occurrences at the western margin of Archaean Bonai granite and overlying Iron Ore Group (IOG) rocks have recently been located over a total strike length of 8–10 km intermittently in a NE-SW to E-W trend with steep dips due north-west to north in parts of Sundargarh district of Orissa. The QPC samples have analysed up to 0.039% U₃O₈ and 0.035% ThO₂ with high concentration of Y (74 to 518 ppm), La(<100 to 880 ppm), Cr ( 126 to 633 ppm), Zr (137 to 1250 ppm) and Pb (31 to 581 ppm). Cellulose Nitrate (CN) film studies of few QPC samples indicated adsorbed uranium over goethite and infiltrated ferruginous material (limonite), secondary uranium as encrustation and fracture filling and discrete sub-rounded grains of monazite, zircon, allanite and rare xenotime in the matrix of QPC as radioactive phases. Higher content of Th over U, elevated concentration of Y and La in QPC eliminates the possibility of its low temperature product by epigenetic processes. Poor correlation of U with elements like Pb, Y, Zr, La and Cr can be explained due to surficial leaching of uranium from QPC after its deposition as reflected by adsorbed U over iron-oxides and low U/Th ratio in QPC in the area.     

Interaction of an antecedent fluvial system with early normal fault growth: Implications for syn‐rift stratigraphy,western Corinth rift (Greece)

Continental ‘overfilled’ conditions during rift initiation are conventionally explained as due to low creation of accommodation compared with sediment supply. Alternatively, sediment supply can be relatively high from the onset of rifting due to an antecedent drainage system. The alluvial Lower Group of the western Plio–Pleistocene Corinth rift is used to investigate the interaction of fluvial sedimentation with early rifting. This rift was obliquely superimposed on the Hellenide mountain belt from which it inherited a significant palaeorelief. Detailed sedimentary logging and mapping of the well‐exposed syn‐rift succession document the facies distributions, palaeocurrents and stratigraphic architecture. Magnetostratigraphy and biostratigraphy are used to date and correlate the alluvial succession across and between fault blocks. From 3·2 to 1·8 Ma, a transverse low sinuosity braided river system flowed north/north‐east to east across east–west‐striking active fault blocks (4 to 7 km in width). Deposits evolved downstream from coarse alluvial conglomerates to fine‐grained lacustrine deposits over 15 to 30 km. The length scale of facies belts is much greater than, and thus not directly controlled by, the width of the fault blocks. At its termination, the distributive river system built small, stacked deltas into a shallow lake margin. The presence of a major antecedent drainage system is supported by: (i) a single major sediment entry point; (ii) persistence of a main channel belt axis; (iii) downstream fining at the scale of the rift basin. The zones of maximum subsidence on individual faults are aligned with the persistent fluvial axis, suggesting that sediment supply influenced normal fault growth. Instead of low accommodation rate during the early rift phase, this study proposes that facies progradation can be controlled by continuous and high sediment supply from antecedent rivers.     

甘肃省文县观音坝古地震事件的研究

通过野外调查在甘肃陇南的文县阳山金矿东北磨坝—观音坝一带首次发现一大套震碎砾岩,这套砾岩由于覆盖在白垩纪红色砾岩之下,故而一直把其当作白垩纪砾岩处理。通过作者参加该项目的研究后认为,是一套震碎角砾岩,这种震碎角砾岩,在国内外尚未见公开报道。它是地质历史上一次浅源强烈地震的岩石记录,反映了该地区一次重要的地震构造运动,同时本文对该地区的震积岩进行了沉积序列及岩石类型划分,这种观点对促进陕甘川地震历史的认知有重要的补充作用。     

重庆地区江北砾岩北碚附中剖面 磁化率特征及其环境意义

选取砾岩层填穴物、砾石层局部胶结填穴物、砂岩层新鲜岩石作为分析样品,运用了磁化率值、¹⁴C测年、磁铁矿含量、氧同位素分析等方法进行测定和研究。结果表明,江北砾岩北碚附中剖面,磁化率值的变化与磁性铁矿含量有较好的一致性,磁化率曲线与氧同位素曲线变化特征具有较好的对应性。江北砾岩北碚附中剖面岩层的磁化率能指示晚更新世晚期的环境变化,包含了2个较短的暖湿期和3个较长的冷干时期,而干冷时期内又存在很短暖湿期。