广西桂林杨堤晚泥盆世弗拉期-法门期之交上、下 Kellwasser事件的差异与海洋生产力变化

对广西桂林晚泥盆世弗拉期-法门期(Frasnian-Famennian,简称F-F)之交杨堤剖面的碳酸盐岩碳同位素、生物成因 Ba、Al、Si和氧化还原指标的综合分析,表明该地区F-F之交生产力较低,且两次Kellwasser事件具有不同特点:下Kellwasser (LKW)事件时期并未出现明显缺氧环境,生态系统中初级生产力和最终生产力均相对较高,δ13C小幅度正偏是由生产力上升 引起;上Kellwasser(UKW)事件时期海平面上升,陆源输入物极少,氧含量急剧下降,初级生产力有所增加,最终生产力锐减, 此时的δ13C大幅正偏是由于缺氧条件下有机碳缓慢积累埋藏保存所致.      

新疆伊吾县伊吾煤矿一带泥盆系下统的发现及地质意义

测区原1∶20万巴里坤哈萨克自治县幅区调马依当的一套岩性为陆源碎屑岩夹灰绿、暗灰色富含钙质的火山碎屑岩,将其划归为石炭系下统姜巴斯套组。通过本次对新疆伊吾县伊吾煤矿一带1∶5万区域地质矿产调查,采集到腕足类化石,经鉴定为阔石燕类:Euryspirifer cf及岩石区域对比,与区域上的泥盆系下统托让格库都克组完全可以对比,为该套地层时代重新厘定为泥盆系下统托让格库都克组。新疆伊吾县伊吾煤矿一带泥盆系下统的发现,对该区具有重要的研究意义:本套地层的厘定为(巴里坤地区)北西向构造带(托里—三塘湖晚古生代沟弧带)的发展演化阶段演提供了重要的基础性地质资料)。     

敦煌三危山地区晚泥盆世斜长花岗岩的发现及其地质意义

本文报道在敦煌三危山地区发现的斜长花岗岩。斜长花岗岩呈细小脉状、网脉状产出,主要由斜长石(60%~65%)和石英(28%~32%)组成,电子探针分析数据显示斜长石属于钠长石-更长石(Ab=85~99),主要为更长石。岩石样品具高硅(Si O2=71.00%~72.92%)、极度富钠、贫钾(Na2O/K2O=8.54~11.37)的特征;Mg#较高,介于47~64;稀土元素含量极低,球粒陨石标准化配分曲线呈近乎平坦型分布,轻、重稀土元素均亏损,Eu、Sr正异常。锆石Hf同位素组成显示εHf(t)为正值,主体介于+3.1~+6.4之间,表明该斜长花岗岩为M型花岗岩。野外地质特征、岩相学特征、地球化学组成和锆石Hf同位素分析均表明该区斜长花岗岩是由起源于亏损地幔源区的洋脊拉斑玄武质熔体中的斜长石堆晶形成的大洋斜长花岗岩,属于蛇绿岩的端元组分,该岩石形成以后经历了后期流体交代作用的改造。LA-ICP-MS锆石U-Pb定年结果显示样品21SWS和SWS05的206Pb/238U加权平均年龄分别为363±2Ma和365±3Ma,表明该斜长花岗岩形成于晚泥盆世。综合区域地质特征及已有研究成果,提出敦煌地区经历了晚古生代洋盆扩张-俯冲过程,360~370Ma的洋盆扩张可能代表了古亚洲洋南缘弧后盆地的扩张;伴随着新元古代开始古亚洲洋的扩张-闭合过程,敦煌地块很可能卷入到了一系列与古亚洲洋闭合相关的造山活动,最终构成了中亚造山带的一部分。     

内蒙古敖汉旗朝吐沟组火山岩LA-ICP-MS锆石U-Pb年龄

内蒙古赤峰敖汉旗一带的朝吐沟组由变基性岩、变质酸性火山岩夹云母石英片岩组成。采用LA-ICP-MS技术,对朝吐沟组2件变流纹岩样品进行了U-Pb同位素测定,获得的锆石206Pb/238U年龄加权平均值分别为359.4±1.4Ma和360.3±1.4Ma,即晚泥盆世法门期,表明朝吐沟组形成于晚泥盆世,而非前人认为的早石炭世。朝吐沟组火山岩石组合为变玄武岩和变流纹岩,显示出典型的双峰式火山岩特征,揭示该区在晚泥盆世处于伸展构造环境。     

长江下游地区晚泥盆世至早石炭世孢子带和泥盆系—石炭系界线

本文系统研究了长江下游地区(包括江苏、浙江和安徽)晚泥盆世和早石炭世孢子50属150余种。根据孢子在地层中的分布和演化规律,建立了7个孢子带,其中晚泥盆世3个带,早石炭世4个带。自下而上依次为:1)Rugospora flexuosa-Grandispora cornuta(FC)带;2)Vallatisporites pusillites-Retispora lepidophyta(PL)带;3)Retispora lepidophyta-Verrucosisporites nitidus(LN)带;4)Vallatisporites verrucosus-Retusotriletes incohatus(VI)带;5)Spelacotriletes pretiosus-Cingulizonates bialatus(PB)带;6)Schopfites claviger-Auroraspora macra(LN)带;7)Lycospora pusilla(PU)带。五通群下部观山组化石孢子丰富,时代相当西欧晚泥盆世法门阶(Famennian)Fa2c-Fa2d。泥盆系和石炭系界线置于陈家边组底部,即3带Retispora lepidophytaVerrucosisporites nitidus(LN)带和4带Vallatisporites verrucosus-Retusotriltes incohatus(VI))带之间。本文还深入讨论了沉积环境、微古植物地理区、国内外比较等问题。     

张家界砂岩地貌成因分析

张家界砂岩地貌特点是:天子山周边,峰丛林景观;赤铁矿红顶,泥盆系砂岩。即:天子山向斜周边为泥盆系地层,下部云台观组和上部黄家磴组构成张家界地貌的母岩地层,新构造运动隆升形成的峰林景观呈现了张家界地貌,石英砂岩顶部坚硬的赤铁矿保护了张家界地貌的形态。张家界地貌形态按照由老到新的发育次序,依次为夷平面、方山、石墙、穿洞、天生桥、峰丛和峰林。印支运动形成NEE向的索溪峪向斜,燕山运动形成NNE向的天子山向斜,张家界地貌围绕天子山向斜周边及索溪峪向斜南东翼发育。     

塔里木盆地上泥盆—下石炭统层序地层格架与古地理

利用110余口钻井的录井和测井资料,结合地震资料,运用沉积学原理和层序地层学原理,建立了塔里木盆地上泥盆-下石炭统层序地层格架.自下而上,塔里木盆地上泥盆-下石炭统发育东河层序(SQd)、巴楚1层序(SQb1)、巴楚2层序(SQb2)、卡拉沙依1层序(SQk1)共4个三级层序,每个层序均可划分出海侵体系域(TST)和高...     

论皖南邓家组、铺岭组

论述皖南地区历舍、贤村剖面青白口纪邓家组、铺岭组的岩石组合、沉积构造、微古植物化石等特征，并对沉积相、原始构造环境进行初步分析。     

Devonian formations,vertebrate faunas and age control on the far south coast of New South Wales and adjacent Victoria

A diverse fossil vertebrate record in the Devonian of coastal southeastern Australia includes at least 30 genera and species representing all three major groups of extant jawed vertebrates (bony and cartilaginous fishes, and tetrapods), and both extinct groups (placoderm and acanthodian fishes). A bone recorded by W. B. Clarke in 1860 from Twofold Bay is the first published record of a Devonian vertebrate from the Southern Hemisphere. Abundant plant remains at some localities include large impressions of arborescent lycopsids, indicating one of the earliest forest environments for the Gondwana supercontinent. An early terrestrial invertebrate fauna is evidenced by fossil millipede remains. A review of the evidence for age control using paleontology and isotopic dating suggests that the lower part of the Devonian sequence (Bunga beds, Boyd Volcanic Complex) may be somewhat older (Emsian – Eifelian) than recently proposed; the tetrapod trackways at Genoa River in Victoria (lower part of the Combyingbar Formation) may correlate with the lowermost Twofold Bay Formation of the Merrimbula Group, which is overlain by the marine Bellbird Creek Formation, a manifestation of the global late Frasnian marine transgression and extinction event. Abundant placoderm remains at all higher fossil fish horizons in the overlying Worange Point Formation indicate a latest Devonian rather than Carboniferous age for the upper Merrimbula Group.     

Discussion: Macrofaunal zonation of Middle Permian coal sequences in Sydney Basin

Three suites of alkaline granite can be recognised in the Narraburra Complex at the triple junction of the Tumut, Giralambone‐Goonumbla and Wagga Zones, central southern New South Wales. On the basis of K₂O/Na₂O ratios, biotite and hornblende‐biotite potassic I‐type granites have been assigned to the Gilmore Hill (K₂O/Na₂O 1.00) and Barmedman Suites (K₂O/Na₂O > 1.2). These are metaluminous to weakly peraluminous suites that crystallised from high‐temperature,reduced magmas with the least fractionated members of each suite having high Ba and low Rb abundances compared to other Lachlan Fold Belt granites. Fractionated members of these suites have high abundances of high‐field‐strength elements, similar to those observed in A‐type granites. Arfvedsonite and aegirine‐arfvedsonite granites have been assigned to the peralkaline Narraburra Suite. Granites from this suite have chemistry consistent with them being the intrusive equivalents of comendites and they are also similar in some respects to A‐type granites: they have, for example, particularly high abundances of Zr. The A‐type signature is, however, at least in part the result of strong fractionation. Total‐rock Rb–Sr isotopic analyses from both I‐type suites plot on the same isochron, giving an age of 365 ± 4 Ma (Sr_l = 0.70388 ± 53). A total‐rock isochron for the peralkaline Narraburra Suite gives a less well‐defined age of 358 ± 9 Ma (Sr_l = 0.7013 ± 80). The Late Devonian Rb–Sr ages may be emplacement ages or a result of resetting during fluid‐rock interaction. Although granites of the Narraburra Complex have geochemical affinities with alkaline granites formed late in orogenic cycles, they post‐date arc magmatism by at least 75 million years and they formed in a within‐plate setting. Magmatism was related to localised reactivation of major faults (Gilmore Fault and the Parkes Thrust) in the region, and to partial melting involving both enriched mantle and Ordovician shoshonitic crustal components. Emplacement of the Narraburra Complex was contemporaneous with magmatism in the Central Victorian Magmatic Province and A‐type magmatism in eastern New South Wales. Collectively, all these magmatic events were related to extension post‐dating amalgamation of the western and central/eastern subprovinces of the Lachlan Fold Belt.