长白山天池火山造锥喷发岩浆演化系列与地层划分

根据天池火山岩的岩性特征、化学成分和产状,把火山造锥喷发划分为4介阶段,同时描述了各个阶段喷发特点和演化规律。将岩浆演化划分为早晚两个旋回,描述了每一旋回的特点及岩性。最后把天池火山地层进行了划分并同邻区地层进行了对比。     

胜利油田东营凹陷中央隆起带断层封闭模式研究

东营凹陷中央隆起带断裂系统复杂,断层封闭性直接控制油气藏形盛分布及油气藏规模,封闭性强的断层附近可形成大规模油气藏,封闭性差的断层附近油气藏规模小,甚至无油气藏形成.以岩性配置封闭模式、主应力封闭模式和泥岩沾污带封闭模式3种最主要的封闭模式为例建立了东营凹陷中央隆起带断层封闭模式.定量分析评价了东营凹陷中央隆起带断层封闭性,认为东营凹陷中央隆起带封闭性断层的最佳断面正应力为40~50 MPa,封闭性断层的泥岩沾污因子常小于2.6.针对某一具体断层判断其是否具有封闭性需多方面综合分析,不可简单地进行单因素分析.      

Impact of the 6 April 2009 L'Aquila earthquake on groundwater flow in the Gran Sasso carbonate aquifer,Central Italy

The Mw = 6·3 L'Aquila earthquake on 6 April 2009 produced a mainshock that caused significant changes in the hydrogeology of the Gran Sasso carbonate fractured aquifer: (i) the sudden disappearance at the time of the mainshock of some springs located exactly along the surface trace of the Paganica normal fault (PF); (ii) an immediate increase in the discharge of the Gran Sasso highway tunnel drainages and of other springs and (iii) a progressive increase of the water table elevation at the boundary of the Gran Sasso aquifer during the following months. Using the data collected since the 1990s that include aftershock monitoring as well as data regarding spring discharge, water table elevations, turbidity and rainfall events, a conceptual model of the earthquake's consequences on the Gran Sasso aquifer is proposed herein. In this model that excludes the contribution of seasonal recharge, the short‐term hydrologic effects registered immediately after the mainshock are determined to have been caused by a pore pressure increase related to aquifer deformation. Mid‐term effects observed in the months following the mainshock suggest that there was a change in groundwater hydrodynamics. Supplementary groundwater that flows towards aquifer boundaries and springs in discharge areas reflects a possible increase in hydraulic conductivity in the recharge area, nearby the earthquake fault zone. This increase can be attributed to fracture clearing and/or dilatancy. Simulations by numerical modelling, related to pore pressure and permeability changes with time, show results in accordance with observed field data, supporting the conceptual model and confirming the processes that influenced the answer of the Gran Sasso aquifer to the L'Aquila earthquake. Copyright © 2010 John Wiley & Sons, Ltd.     

Early Carboniferous blueschist facies metamorphism in metapelites of the West Sudetes (Northern Saxothuringian Domain,Bohemian Massif)

The metamorphic evolution of micaschists in the north‐eastern part of the Saxothuringian Domain in the Central European Variscides is characterized by the early high‐pressure M1 assemblage with chloritoid in cores of large garnet porphyroblasts and a Grt–Chl–Phe–Qtz ± Pg M2 assemblage in the matrix. Minerals of the M1–M2 stage were overprinted by the low‐pressure M3 assemblage Ab–Chl–Ms–Qtz ± Ep. Samples with the best‐preserved M1–M2 mineralogy mostly appear in domains dominated by the earlier D1 deformation phase and are only weakly affected by subsequent D2 overprint. Thermodynamic modelling suggests that mineral assemblages record peak‐pressure conditions of ≥18–19 kbar at 460–520 °C (M1) followed by isothermal decompression 10.5–13.5 kbar (M2) and final decompression to <8.5 kbar and <480 °C (M3). The calculated peak P–T conditions indicate a high‐pressure/low‐temperature apparent thermal gradient of ～7–7.5 °C km^?1. Laser ablation inductively coupled plasma mass spectrometry isotopic dating and electron microprobe chemical dating of monazite from the M1–M2 mineral assemblages give ages of 330 ± 10 and 328 ± 6 Ma, respectively, which are interpreted as the timing of a peak pressure to early decompression stage. The observed metamorphic record and timing of metamorphism in the studied metapelites show striking similarities with the evolution of the central and south‐western parts of the Saxothuringian Domain and suggest a common tectonic evolution along the entire eastern flank of the Saxothuringian Domain during the Devonian–Carboniferous periods.     

Multiple growth of garnet,sillimanite/kyanite and monazite during amphibolite facies metamorphism: implications for the P–T–t and tectonic evolution of the western Altai Range,Mongolia

Four amphibolite facies pelitic gneisses from the western Mongolian Altai Range exhibit multistage aluminosilicate formation and various chemical‐zoning patterns in garnet. Two of them contain kyanite in the matrix and sillimanite inclusions in garnet, and the others have kyanite inclusions in garnet with sillimanite or kyanite in the matrix. The Ca‐zoning patterns of the garnet are different in each rock type. U–Th–Pb monazite geochronology revealed that all rock units experienced a c. 360 Ma event, and three of them were also affected by a c. 260 Ma event. The variations in the microstructures and garnet‐zoning profiles are caused by the differences in the (i) whole‐rock chemistry, (ii) pressure conditions during garnet growth at c. 360 Ma and (iii) equilibrium temperatures at c. 260 Ma. The garnet with sillimanite inclusions records an increase in pressure at low‐P (~5.2–7.2 kbar) and moderate temperature conditions (~620–660 °C) at c. 360 Ma. The garnet with kyanite inclusions in the other rock types was also formed during an increase in pressure but at higher pressure conditions (~7.0–8.9 kbar at ~600–640 °C). The detrital zircon provenance of all the rock types is similar and is consistent with that from the sedimentary rocks in the Altai Range, suggesting that the provenance of all the rock types was a surrounding accretionary wedge. One possible scenario for the different thermal gradient is Devonian ridge subduction beneath the Altai Range, as proposed by several researchers. The subducting ridge could have supplied heat to the accretionary wedge and elevated the geotherm at c. 360 Ma. The differences in the thermal gradients that resulted in varying prograde P–T paths might be due to variations in the thermal regimes in the upper plate that were generated by the subducting ridge. The c. 260 Ma event is characterized by a relatively high‐T/P gradient (~25 °C km^?1) and may be due to collision‐related granitic activity and re‐equilibrium at middle crustal depths, which caused the variations in the aluminosilicates in the matrix between the rock units.     

西准噶尔走滑断裂系元素分布特征及其成矿意义

我国新疆西北部西准噶尔走滑断裂构造体系(简称"西准系")是中亚造山带巴尔喀什马蹄形构造的向东延伸部分,由于中生代成吉思-准噶尔断裂的右行走滑断裂作用而被分成了两个部分。西准系是一个多米诺式的走滑断裂构造体系,主要由达拉布特断裂、玛依勒断裂、巴尔鲁克断裂等三条NE走向的左行走滑断裂及其夹在它们之间的地块所组成,可能是晚古生代与走滑断裂相关的陆条弯曲(褶皱)作用的产物。同时,西准噶尔地区也是重要的晚古生代成矿带,产出有一些大型和超大型的金属矿床,包括包古图斑岩铜矿、哈图金矿、萨尔托海铬铁矿和杨庄铍矿床等。本文分析了西准系走滑断裂构造与元素分布之间的关系。结果显示,西准噶尔成矿带元素与地球化学块体以及铜、金、钼、铬铁矿等矿床的分布,均受晚古生代西准系的形成与演化过程的控制。其中,庙尔沟、红山岩体与金地球化学块体之间的反对称分布特征,说明了花岗岩类侵入体和金元素在达拉布特断裂左行走滑过程中发生了重要的物质调整与迁移作用。庙尔沟岩体的逆时针旋转运动,造成了环状断裂与裂隙系统,以及与之相对应的Cu、Pb等元素风火轮式的分布形式。走滑断裂作用与岩体旋转运动的共同结果,导致了金元素沿断裂和裂隙的迁移与成矿,使得西准地区金矿床在断裂和裂隙中的发育。断裂构造体系与元素地球化学异常之间的关系,可以用来有效指导西准地区未来矿产资源的勘查。     

黔中隆起东部龙里—凯里地区油苗有机地球化学特征及其成因分析

黔中隆起东部发现有大量的中—古生界油苗。应用色谱、色谱-质谱及同位素等测试技术,系统地研究了油苗的地球化学特征及油源。结果表明,受黔中多期次构造抬升活动的影响油苗的热演化程度均处于成熟阶段;大冶组(T1d)原油的生物标志物、族组分及单体烃碳同位素组成与古生界油苗存在明显差异,其烃源岩为研究区西南部的T1d油页岩;茅口组(P2m)原油为单源供烃,与栖霞组(P1q)烃源岩具亲缘关系;红花园组(O1h)原油具混源特征,主要来源于下寒武统牛蹄唐组,同时受翁项群组(S2w)泥质岩段的影响。其中,S2w泥质岩段具晚期生烃的特征,预示着研究区下古生界存在一套特殊的含油气组合,这对评价该地区的油气前景具积极意义。     

芬兰北部金矿床产出环境、地质特征和成矿作用

芬兰北部的金矿床数量众多,大多数金矿床(点)产出于古元古界中央拉普兰绿岩带(CLGB)和库萨莫—帕拉波加片岩带内,主要分为3种类型:造山型金矿、铁氧化物铜-金(IOCG型)矿床及砂金矿。其中造山型金矿绝大部分分布于中央拉普兰绿岩带中部及库萨默地区和帕拉波加地区,最常见的矿石矿物为黄铁矿、毒砂、黄铜矿和磁黄铁矿,其次为方铅矿、闪锌矿、黝铜矿等。围岩蚀变包括钠长石化、绢云母化、黑云母化、碳酸盐化及绿泥石化。造山型金矿床主要控制因素包括构造、岩性和造山期区域变质。IOCG型矿床主要分布在CLGB的西部克拉瑞地区,容矿围岩是钠长石-直闪石石棉型岩石,矿石中富含Fe-Cu-Au±Ag、Bi、Ba、Co、Mo、Sb、Se、Te、Th、U和轻稀土元素。围岩蚀变强烈,并且有明显的分带现象。IOCG型金矿床的形成受岩浆热液活动和构造的影响较大。砂金矿床包括古砂金矿床和现代砂金矿床,主要分布在CLGB东北部。芬兰北部金矿床的研究对北极圈及邻区的找矿勘查工作具有重要意义,也为中国胶东半岛、华北克拉通北缘、小秦岭和秦岭地区及新疆北部地区进一步金矿勘查提供参考。     

The nautiloid Family Eothinoceratidae from the Floian of the Central Andean Basin (NW Argentina and South Bolivia)

A single confidently dated species of cephalopod is so far known in the Tremadocian of the southern Central Andean Basin (NW Argentina and southern Bolivia). This species belongs to the Eothinoceratidae and has a strong affinity mainly with Avalonia. During the Floian, a notable increase in diversity took place, with the appearance of a variety of families represented by several genera, in particular, within the Family Eothinoceratidae. In addition to the previously described species from southern Bolivia, we evaluate the other records of that family from the Central Andean Basin, and propose the following new taxa: Saloceras sikus sp. nov., Saloceras quena sp. nov., Mutveiceras gen. nov., and Mutveiceras cienagaensis sp. nov. We also describe Margaritoceras diploide, Margaritoceras sp., and Mutveiceras sp. From a palaeogeographic perspective, the cephalopod fauna shows affinities mainly with those of England, Wales, and the Montagne Noire (cold water Gondwana and peri‐Gondwana). As with other cephalopod faunas of mid to high palaeolatitudes, eothinoceratids occur along with other cephalopods forming assemblages of low morphological diversity. We interpret the forms described here as demersal with a subvertical poise, but capable of making rapid buoyancy changes, living in a wide spectrum of shallow offshore to shoreface settings. Copyright © 2014 John Wiley & Sons, Ltd.     

Trace and rare earth element geochemistry of the Upper Triassic mudstones in the southern Ordos Basin,Central China

Oil‐source correlation studies have demonstrated that the crude oils in the Ordos Basin were mainly derived from organic‐rich lacustrine mudstones of the Yanchang Formation. The sedimentology, petrology and organic geochemistry of these mudstones have been studied intensively, but their trace and rare earth element (REE) characteristics have received little attention. In this paper, we present trace and rare earth element data of the Upper Triassic Yanchang Formation mudstones in the southern Ordos Basin to constrain the palaeoenvironment, provenance and depositional setting. Our results show that the REE and trace element concentrations of the Yanchang Formation mudstones are higher than those of the upper continental crust (UCC). The Sr contents and Sr/Ba and Y/Ho ratios of these mudstones indicate the absence of a marine transgression during the sedimentation of the Upper Triassic mudstones. The depositional environment of the Upper Triassic mudstones was slightly oxic as evidenced by the values of Eu/Eu*, Ce/Ce*, Ce_anom, δU, U/Th, V/Cr and Ni/Co. The UCC‐normalized distribution pattern of REEs, spider diagrams, the ratios of related elements, the bivariate diagrams of Th/Sc–Zr/Sc and La/Th–Hf and the ternary plots of La–Th–Sc and Th–Sc–Zr/10 signify that the provenances of the Chang9–7 mudstones were mainly derived from a continental island arc, whereas the provenances of the Chang6–3 mudstones were mainly derived from a mixture of continental island arc and active continental margin, and the latter contain less recycled materials. Combined with the previous studies of detrital zircon dating and petrography of the Yanchang Formation sandstones in the southern Ordos basin, we propose that the Qinling orogenic belt served as one of the primary source regions occurring between the Chang7 and Chang6 periods, corresponding to the initial uplift of the west Qinling Mountains due to the collision between the Yangtze and North China blocks. Copyright © 2014 John Wiley & Sons, Ltd.