新疆西准噶尔北部布尔津县木斯塔巴岩体年代学、地球化学特征及地质意义

准噶尔是新疆北部古生代造山带的重要组成部分,以广泛发育晚古生代花岗岩为特征,是中亚造山带总显生宙陆壳生长作用非常显著的地区之一。根据最新获得的LA-ICP-MSU-Pb锆石年龄,木斯塔巴岩体锆石年龄为(303±2.0) Ma(晚石炭世),岩石地球化学分析,岩石具高硅(66.04%~70.4%),高碱(2.26~2.87),高铝(13.25%~15.46%),高钾(3.4%~4.58%),低镁,A/CNK=1.06~1.22,低固结(6.34~12.87),高分异(78.35~84.5),富轻稀土(LREE/HREE=3.57~12.97)和大离子亲石元素K,Rb,Ba,Sr,亏损高场强元素Nb,Ta,Ti,P,为过铝质高钾钙碱性系列花岗岩,具碰撞花岗岩特征,属额尔齐斯构造带的重要组成部分,其形成与板块俯冲作用关系密切。本区石炭纪花岗岩的数据与北准噶尔地区对比,显示晚石炭世额尔齐斯构造带闭合,进入后碰撞阶段。     

兴蒙造山带南段白音图嘎地区A型花岗岩地球化学特征及其对古亚洲洋演化的制约

关于兴蒙造山带晚石炭世-早二叠世A型花岗岩成因及其形成构造背景目前仍存在分歧。本文针对兴蒙造山带南段白音图嘎地区二长花岗岩和碱长花岗岩开展了锆石U-Pb年代学以及全岩地球化学研究,从而探讨其岩石成因以及对晚古生代该区构造演化的制约。分析结果显示:二长花岗岩和碱长花岗岩的锆石LA-ICP-MSU-Pb年龄分别为312±2Ma和294±2Ma,为晚石炭世和早二叠世岩浆活动产物。两者具有相似的地球化学组成,都有高硅(SiO_2=70.83%～73.85%)、高钾(K_2O=5.66%～7.97%)、高碱(Na_2O+K_2O=9.87%～13.29%)、低铝(Al_2O_3=10.72%～12.93%)、低钙镁(CaO=0.19%～1.22%,MgO=0.10%～0.26%)和低磷钛(TiO_2=0.01%～0.25%, P_2O_5=0.03%～0.21%)的特征,均强烈亏损Ba、Sr、P、Ti、Eu,弱亏损Nb、Ta等元素,具有较弱的轻重稀土元素分异以及强负Eu异常((La/Yb)N=2.4～5.8,Eu/Eu*=0.05～0.66),岩石类型都为过碱质A型花岗岩。此外,岩石还富K贫Na,低Ga、Ce,高Y,低Rb/Ba、K/Rb值。岩石地球化学特征显示其为新生下地壳熔融,源区富含辉石和钾长石,缺乏石榴子石和黑云母,形成于后碰撞伸展背景中,而古亚洲洋在312Ma年前就已闭合。综合区域构造演化史以及同时代岩浆岩的年代学和地球化学特征表明,由于早石炭世古亚洲洋俯冲板片后撤和弧后拉张作用的影响,贺根山洋在白音宝力道弧后打开。在晚石炭世造山后伸展大背景下还存在着小规模的晚石炭世-早二叠世俯冲-碰撞造山运动,从而导致区域上晚石炭世-早二叠世同时存在钙碱性岛弧火山岩以及后碰撞A型花岗岩。     

内蒙古浩尧尔忽洞金矿区花岗岩岩石成因及构造意义

内蒙古浩尧尔忽洞金矿为低品位超大型中低温热液型金矿,矿区内海西期花岗岩发育.在矿区内可见黑云花岗岩、花岗细晶岩、花岗伟晶岩和花岗斑岩.花岗岩中SiO2含量65.36％ ～74.29％,Na2O/K2O比值0.43 ～1.01,平均值为0.75,花岗脉岩类属于高钾钙碱性,黑云花岗岩属于钾玄岩系列.哈克图解上各元素含量随SiO2变化呈线性规律明显,具Ⅰ型花岗岩特征.∑REE值在64.86×10-6～164.80×10-6范围内变化,总体上稀土含量较低.（La/Yb）N值为6.59 ～ 16.98,显示轻重稀土有明显的分馏.稀土元素蛛网图表现为右倾.黑云母花岗岩δEu平均值0.30,具低Sr低Y的特点.花岗脉岩类δEu平均值为0.65,表现出高Sr低Y的特点.花岗岩类具有中等到强的铕亏损.根据其地球化学特征,认为该岩体为同碰撞—后碰撞期形成的高钾钙碱性Ⅰ型花岗岩.     

北京石城闪长岩和云蒙山花岗岩岩石地球化学特征及成因

云蒙山岩基位于云蒙山变质核杂岩下盘,主要由石城闪长岩及云蒙山花岗岩组成。石城闪长岩属高钾钙碱性系列岩石,富镁贫铁,过铝指数ACNK值均小于1,属准铝质岩石;富集大离子亲石元素和轻稀土元素,亏损高场强元素,具无或弱的Eu负异常,Sr/Y比值极高,是具有高Sr低Y微量元素特征的中性岩浆岩。云蒙山花岗岩属高钾钙碱性系列岩石,且(Na2O-2)/K2O1,属钾质火成岩,富铁,过铝指数ACNK值略大于1,属弱过铝质岩石;富集大离子亲石元素,强烈富集轻稀土元素,亏损高场强元素,Sr/Y和(La/Yb)N比值高,属典型的"C型埃达克岩"。二者均显示EM-I型富集岩石圈地幔的SrNd同位素印迹。具有高Sr低Y微量元素特征的石城闪长岩形成于燕山地区中侏罗世挤压运动幕(约180Ma~170Ma)和晚侏罗世晚期—早白垩世最早期挤压运动幕(约151Ma~135Ma)之间的伸展背景,是基性岩浆分离结晶作用的产物,在其演化过程中与地壳围岩之间发生了同位素的混染。云蒙山花岗岩形成于挤压构造背景之中,为燕山地区晚侏罗世晚期—早白垩世最早期挤压运动幕(约151Ma~135Ma)岩浆活动的代表,是华北克拉通下地壳富Mg或Mg#高的古老基性岩类在高压(P≥1.5GPa)下失水部分熔融的产物。     

北祁连金佛寺岩体地球化学特征及构造意义

金佛寺岩体为北祁连华力西早期形成的一个较大的复式深成岩基,主要岩石类型为二长花岗岩、黑云二长花岗岩和正长花岗岩,为高钾钙碱性岩系,具高钾、高铝和低钛的特点;REE分布模式为弱Eu异常;在Peace的Rb-Y-Nb图解中位于后碰撞花岗岩类区。岩体的同位素锆石U-Pb年龄为345.0±75.0Ma,代表其形成时代为晚泥盆世...     

辽南盖州卧龙泉岩体LA-ICP-MS锆石U-Pb年龄及岩石地球化学特征

卧龙泉岩体分布于辽宁南部盖州市卧龙泉镇,岩性主要为似斑状黑云母二长花岗岩,岩石锆石²⁰⁶Pb/²³⁸U年龄加权平均值为1888.4±5.3 Ma,形成时代为古元古代.卧龙泉似斑状黑云母二长花岗岩地球化学特征显示,Na₂O/K₂O均值为0.70,属高钾钙碱性系列;里特曼指数σ平均值为2.18,属钙碱系列;铝饱和指数A/CNK平均值为1.16,属过铝型;岩石中稀土元素总量平均值为299.04×10^-6,稀土元素配分模式右倾,属具中负铕异常的轻稀土富集、重稀土亏损型,富集大离子亲石元素,亏损高场强元素,具有活动陆缘钙碱性岩系特征,属于同碰撞科迪勒拉型（I型）花岗岩,应与古元古代造山运动造成下地壳加厚熔融有关.     

内蒙古哈珠地区晚古生代花岗岩类成因及其构造意义

系统研究了北山造山带北部哈珠地区花岗岩类的年代学、地球化学和锆石Hf同位素特征,并据此探讨了岩体的成因及其对晚古生代构造岩浆演化的制约.锆石LA-MC-ICP-MS U-Pb测年结果显示花岗闪长岩（298.6±1.7 Ma）和二长花岗岩（306.0±1.3 Ma）、碱长花岗岩（289.3±1.3 Ma）分别为晚石炭世晚期、早二叠世岩浆活动的产物.花岗闪长岩、二长花岗岩化学组成上表现为中钾钙碱性、Mg#值较低,分异程度中等（D.I.=79.2~86.9）,属准铝质、镁质岩石;碱长花岗岩则表现高硅、富碱、准铝,贫钙、镁、铁,分异程度高（D.I.=94.4~96.5）.三者均富集Rb、Ba、Th、U、La、Ce等,不同程度亏损高场强元素Nb、Ta、P、Ti、Sr、Eu.花岗闪长岩、碱长花岗岩样品的ε_Hf（t）均为正值,T_DMC主要集中于450~800 Ma.本文和最近获得的数据表明,俯冲板块脱水交代新生下地壳,并诱发新生地壳的部分熔融,形成晚石炭世花岗岩类;早二叠世由于后碰撞伸展作用导致岩石圈拉伸减薄,促使新生地壳部分熔融,再经高程度的分异演化形成本文碱长花岗岩.      

西准噶尔A型花岗岩地球化学特征及找矿意义

西准噶尔地区广泛发育晚古生代后碰撞花岗岩,年龄多集中于300Ma左右,在时代上属于晚石炭世,A型花岗岩具有具有高硅、低铝、富碱、准铝质-弱过铝质、贫钙、低镁,10000×Ga/Al比值较大,强烈富集高场强元素(HFSE)及Zr、Y、Ga等元素,Sr、Ba强烈亏损,稀土配分模式图呈现典型的右倾“海鸥型”等,并且在A1—A2型花岗岩判别图解显示具有典型的铝质A型的A2型花岗岩特征,表明A型花岗岩可能是年轻地壳(洋壳和岛弧)部分熔融形成的美云闪长-花岗闪长岩质岩浆经进一步分离结晶作用的产物,具备规模成矿的条件.     

滇西南勐海布朗山奥陶纪花岗岩锆石U-Pb年龄、Hf同位素组成特征及其构造意义

对滇西南勐海布朗山花岗岩进行LA-ICP-MS锆石U-Pb年龄测试,获得该花岗岩的~(206)Pb/~(238)U年龄加权平均值为458.5±3.0Ma(n=21,MSWD=2.3),属中—晚奥陶世的产物。样品锆石的ε_(Hf)(t)变化范围为-2.4～0.9之间,平均值为-0.9;亏损地壳模式年龄tDMC变化范围为1.41～1.58Ga,加权平均值为1.49Ga。岩石地球化学特征表明,该花岗岩具有高SiO_2(75.79%～77.56%)、富碱(K_2O+Na_2O=7.39%~8.42%)、中-高钾(K_2O/Na_2O=1.23～1.95)、低MgO(0.14%～0.27%)、低CaO(0.05%～0.64%)的特征。铝过饱和指数A/CNK值介于1.02～1.27之间,岩石属高钾钙碱性强过铝S型花岗岩。岩石稀土元素总体表现为由轻稀土元素富集型向平坦的"海鸥"型过渡,具强烈负Eu异常,δEu值为0.03～0.14;在原始地幔标准化微量元素蛛网图上,明显富集Rb、Th、Nd、Ta等元素,具有明显的Ba、Sr、P、Ti亏损。结合区域地质资料分析,该岩体的形成可能与原特提斯洋俯冲,以及古特提斯洋扩张成盆时,该区处于强烈挤压状态,持续的俯冲使澜沧陆壳残片地壳不断加厚并导致区域重力均衡隆升,引起深部地壳物质在加热后抬升减压发生部分熔融有关。     

兴安地块东北部晚侏罗世C型埃达克质花岗岩年代学、地球化学特征及构造环境意义

大兴安岭地区发育强烈的中生代岩浆作用,一直以来是本地区地质构造研究的热点,但关于晚侏罗世花岗岩的研究报道较少。文中根据三件花岗岩样品的锆石U-Pb LA-ICP-MS测年结果获得的(158.5±1.6) Ma、(156.1±0.59) Ma和(154.1±1.1) Ma年龄结果将兴安地块东北部原定为早中生代的花岗岩形成时间厘定为晚侏罗世。该晚侏罗世花岗岩以中粗粒花岗闪长岩—二长花岗岩为岩石组合,岩石具富硅碱、高钾、过铝、低铁钛镁等特点,属于过铝质高钾钙碱性系列,富集LREE,亏损HREE、Y和HFSE,高Sr,低Yb,高La/Yb、Sr/Y比值,具有“C型”埃达克质岩的特点。该花岗岩的形成与蒙古鄂霍茨克洋闭合引起的陆陆碰撞造山作用密切相关,岩浆源于造山带加厚的下地壳底部基性岩的部分熔融,岩浆形成演化中有富铝地壳物质的加入。该系列花岗岩与紧邻的早、中侏罗世TTG花岗岩反映侏罗纪蒙古鄂霍茨克洋经历了由洋壳俯冲到陆陆碰撞的构造演化。     

对吉林省“晚印支亚构造层”归属的一点认识

本文对吉林省“晚印支亚构造层”的归属进行了重新认识,建立了“晚印支—燕山亚构造层”,这一认识可以通过上三叠统沉积建造、地层接触关系,构造变形特征及构造格局转化加以证明,并与按大地构造性质所划分的构造层具有一致性。     

广西象州崖脚晚泥盆世—晚石炭世巴平组的地质时代

本文通过重新测制剖面和补充采样,系统检查和研究了崖脚剖面晚泥盆世晚期—晚石炭世早期牙形石生物地层。通过对在17个牙形石样品中获得的丰富的牙形石材料鉴定,厘定了一些重要牙形石分类。在此基础上,根据牙形石垂向分布特征,确定了带化石的层位。崖脚剖面五指山组上部和巴平组划分出7个牙形石带:五指山组上部为Palmatolepis graciliss辔moidalis带;巴平组下段分别为Siphonodella duplicate带,S.crenulata带,S.isosticha带,Scaliognathus preaanchoralis带和S.anchoralis带下部;巴平组上段为S.anchoralis带上部和Declinognathodas noduliferus noduliferus亚带;巴平组的牙形石带特征显示巴平组的地质时代为晚泥盆世—晚石炭世早期。巴平组地质时代的确定为不同相区层序地层划分,特别是对早石炭世斜坡相区地层划分与对比提供了可靠的依据。     

藏北双湖地区才多茶卡一带构造混杂岩中发现晚泥盆世和晚二叠世放射虫硅质岩

报道了在西藏北部双湖才多茶卡地区新发现的晚泥盆世和晚二叠世放射虫硅质岩,实测剖面的第9层硅质岩以产Neoalbaillella动物群为特征,其中N.ormithoformis,N.optima是晚二叠世长兴阶的2个带化石;第14层硅质岩以产Entactinids动物群为特征,其中Stigmosphaerostylusoumonhaoensis,Triloneheechinata,Archocyrtiumriedeli等主要见于晚泥盆世法门阶。上述2个动物群在西藏尚属首次发现。才多茶卡地区晚古生代放射虫硅质岩的发现为重新认识双湖构造混杂岩带的形成时代、构造环境、“构造带是否东延”等重大地质问题,提供了新的重要资料。     

晚石炭世腕足动物古生物地理区

本文详细研究了晚石炭世腕足动物地理分布，辅之以、双壳和植物等资料，确定了晚石炭世腕足动物的三个古生物地理大区（ｒｅａｌｍ）：冈瓦纳大区；古地中海大区；北极大区。指出冈瓦纳和北极大区为凉水型腕足动物大区，古地中海大区为暖水型的腕足动物大区。将古地中海大区进一步划分为区（ｐｒｏｖｉｎｃｅ），小区（ｓｕｂｐｒｏｖｉｎｃｅ），并指出了北美北部阿舍尔期古生物地理的变化。筛选出了各大区、区及小区的腕足动物特征属，简要叙述各大区、区及小区腕足动物群分布情况。     

The age and formation mechanisms of Late Triassic fissure deposits,Gloucestershire, England: Comments on Mussini,G. et al. (2020). Anatomy of a Late Triassic Bristol fissure: Tytherington fissure 2

In the Late Triassic the landscape NE of present-day Bristol, SW England was dominated by Carboniferous Limestone ridges and cuestas that became progressively buried by continental Mercia Mudstones and finally inundated during the Rhaetian marine transgression. Mussini et al. (2020) adopt the assertions of earlier collaborators back to Whiteside and Marshall (2008) that terrestrial vertebrate assemblages from sediments contained within karstic fissure systems in the former limestone ridges at Cromhall, Tytherington and elsewhere are restricted to the Rhaetian. We review and reject the sedimentological, stratigraphic, geomorphological and topographic arguments for this and reassert a long pre-Rhaetian (Norian) history for the vertebrate-bearing fissure systems at both Tytherington and Cromhall. We also reject the contemporaneous Rhaetian freshwater-seawater mixing zone dissolution model for the fissure systems adopted by Mussini et al. (2020) and reaffirm that the Tytherington and Cromhall fissures developed as conduit caves with a long Triassic history. Applying a new regional study of the Rhaetian transgressive surface, we also show that whilst the fissures at Cromhall remained sealed after the Norian, those at nearby Tytherington were re-exposed in the Late Rhaetian. Already partially filled with Norian sediments, the Tytherington fissures were subject to reworking on the seabed. Internal collapses, probably triggered by well documented repeated regional seismicity, led to the chaotic state of the Tytherington fills when downward moving Rhaetian marine components came to lie amongst and mix with earlier Norian terrestrial sediments. The vertebrate associations in the Tytherington fissures therefore contain a substantial Rhaetian input whilst those at Cromhall do not.     

Late Quaternary environmental phases in the Eastern Cape and adjacent Plettenberg Bay-Knysna region and Little Karoo, South Africa

Four major climato-environmental phases have been identified in the Eastern Cape, Plettenberg Bay-Knysna region and Little Karoo between somewhat before ∼40 000 cal. a BP and the present: the Birnam Interstadial from before 40 000 cal. a BP until ∼24 000 cal. a BP; the Bottelnek Stadial (apparently equating with the Last Glacial Maximum) from ∼24 000 cal. a BP until before ∼18 350 cal. a BP; the Aliwal North (apparently equating with the Late Glacial) from before ∼18 350 cal. a BP until ∼11 000 cal. a BP; the Dinorben (apparently equating with the Holocene) from ∼11 000 cal. a BP until the present. The evidence for, and the characteristics of, these phases is briefly described.     

The upper Coniacian to upper Santonian drowned Arabian carbonate platform,the Mardin-Mazidag area,SE Turkey: Sedimentological,stratigraphic, and ichthyofaunal records

A measured stratigraphic section including the upper Coniacian – upper Santonian interval in the Mardin-Mazidag area in Southeastern Turkey lies on the Arabian Platform and documents the drowning of the Arabian platform. The studied succession transgressively overlies the exposed carbonate platform and exhibits a relatively condensed sequence characterized by presence of fish remains, phosphate nodules, oncoids, phosphatic fragments, glauconites and planktonic foraminifera. Calcareous nannofossils attest a late Coniacian to late Santonian age (zones UC11 UC12). Numerous elasmobranch teeth are also present in this pelagic facies, representing mackerel sharks (Squalicorax, Pseudocorax and Scapanorhynchus) and a ray (Ctenopristis). The presence of pelagic facies and phosphate deposits on the drowned platform may indicate a sudden rise of sea level and increase of nutrient due to upwelling currents. The collapse parts of the Arabian carbonate platform occurred earlier than previously reported, starting from late Coniacian-Santonian onwards.     

Sympatry of two ankylosaurs (Hungarosaurus and cf. Struthiosaurus) in the Santonian of Hungary

A complete and well-preserved right ankylosaurian humerus from the Upper Cretaceous (Santonian) Csehbánya Formation of Iharkút, western Hungary is described here. Based on its osteological features and 21.5 cm adult length, the new specimen is markedly different from the slender humerus of Hungarosaurus, the previously known ankylosaur from the locality, and more similar to that of Struthiosaurus. Thus, the new Hungarian specimen is tentatively assigned here to cf. Struthiosaurus thereby dating back the first occurrence of this genus to the Santonian. The new fossil demonstrates the sympatric co-existence of two different nodosaurid ankylosaurs (a smaller, robust form with 2–2.5 m total body length and a larger, cursorial form with 4–4.5 m body length) in the Iharkút fauna. This also suggests that the pattern of the European ankylosaur diversity was more complex than previously thought.     

Sclerobiont assemblages on the late Eocene bivalve Carolia placunoides: Composition,distribution and their paleoecological significance

Here we describe the composition and distribution of sclerobionts on the late Eocene bivalve Carolia placunoides and provide information about its paleoecology. More than 250 shells were collected from the Temple Member of the Qasr El-Sagha Formation exposed in El-Fayum Province. Nine ichnogenera have been recorded including Gastrochaenolites, Maeandropolydora, Caulostrepsis, Entobia, Centrichnus, Belichnus, Anellusichnus, Oichnus and Trypanites. The dense population of borings made by boring bivalves, Gastrochaenolites, is the most remarkable. Encrusters include serpulid worms (Spirobranchus cf. luxata), balanoid barnacles, and oysters. Shells of juvenile Carolia were the most dominant encrusters. Sclerobionts occurred on left and right valves; they apparently favoured the interior surfaces on both valves but they preferred no special sites. The Carolia placunoides shell concentration is interpreted as para-autochthonous assemblage.     

青海都兰晚石炭世牙形类的发现

青海都兰晚石炭世牙形类的发现１季强（地质矿产部中国地质博物馆北京１０００３４）青海都兰地区石炭纪地层分布广泛，均属浅水相台型沉积，含有丰富的珊瑚、腕足类、类等底栖化石，尤以大海滩、关角牙河和落山一带出露最佳。６０年代，青海省地质矿产局区域地质测量队...