全球早古生代造山带(Ⅲ):华南陆内造山

华南早古生代加里东期变形、岩浆、沉积等特征表现为陆内造山带特征。通过对加里东期角度不整合分布、褶皱、断裂逆冲极性等特征的分析,发现大明山、大瑶山地区EW轴向的寒武系褶皱不对称性和角度不整合空间上向北的拓展变新规律,指示晚寒武世—早奥陶世的由南向北推覆挤压可能是云开、滇—桂北越地块依次向北推挤的结果;从全球背景看,可能和华南陆块南部一些地块与冈瓦纳大陆北缘依次碰撞接触导致的远程陆内效应有关。然而,湘赣边境、桂北元宝山及越城岭地区的早古生代NE向褶皱不对称性指示向西拓展,这可能是由于华夏地块与扬子地块在晚奥陶世—早志留世沿郴州临武断裂陆内收缩挤压的结果,其全球背景可能和华南陆块顺时针旋转与冈瓦纳全面碰撞相关。总之,加里东期构造运动总体由南向北、由东向西渐新,变形强度由强到弱的特征,反映华南陆内碰撞造山事件的根本原因是其与冈瓦纳北缘碰撞的远程效应。450~420 Ma华南已经属于冈瓦纳北缘一部分。     

下扬子盆地石炭纪层序地层研究及盆地演化

以层序地层学概念，探讨石炭纪的下扬子盆地—陆表海盆地。下扬子盆地的石炭系，沉积厚度薄，岩相变化大，界面多而不清晰。研究结果表明，它可以分为 6个三级层序，而且层序的界面大多数与组的界限相吻合。层序 A由金陵组的碎屑岩和灰岩组成；层序 B由高骊山组碎屑岩组成；层序 C由和州组碳酸盐岩组成；层序 D由黄龙组底部碎屑岩和白云岩组成；层序 E由黄龙组中、上部灰岩组成；层序 F由船山组灰岩组成；其中层序 A、 B、 E属于Ⅱ型层序，层序 C、 D、 F属于Ⅰ型层序。石炭纪下扬子海盆的演化可以分为 3个阶段，即坳陷、隆起、扩展沉陷阶段，它们分别对应于层序 A－ B、 C和 D－ F。     

准噶尔盆地火山岩分类研究与应用

岩石分类一直是人们长期探索的课题。由于油气勘探的需要,针对储层研究的盆地火山岩分类已经成为火成岩研究的重要新方向。在综合分析国内外火山岩分类研究的基础上,根据3条野外剖面和21口钻井岩心岩屑的观察描述、岩石薄片鉴定和化学成分分析等资料,依照结构-成分-成因分类原则,建立了适于储层评价的准噶尔盆地石炭系火山岩及其他岩类的岩性分类体系和识别标准。将本区火山岩划分为火山熔岩、火山碎屑熔岩、火山碎屑岩、沉火山碎屑岩等4大类;同时将盆地内与火山岩共生的其他岩类也进行分类和识别,共划分出8大类45种基本类型。与我国东部的中新生代盆地火山岩不同,本区古生代火山岩普遍遭受较长期风化改造和蚀变作用,常见有绿泥石化、碳酸盐化和黏土矿化。这些蚀变会影响到TAS图解岩性判别的结果,因此笔者探讨了蚀变条件下的岩石识别和定名方法。本文分类体系针对火山岩储层研究,结果显示,基于该分类体系岩性与储集空间的类型及其变化规律呈现明显相关性,不同岩性的储集空间类型、组合方式和发育程度存在差异,由此可指导火山岩油气勘探。     

大同地区早中生代煌斑岩—碳酸岩岩墙群

大同地区密集分布的岩墙群由基性－超基性煌斑岩和碳酸岩组成,侵入石炭－二叠纪煤层中。与地层的接触关系和Rb-Sr,K-Ar同位素年代学数据表明墙群的侵位于晚三叠世。Sr,Nd同位素比值显示,碳酸岩和煌斑岩都来源于壳幔混合型岩浆源区。稳定元素比值和相容,不相容元素同等富集则表明是碳酸岩和硅酸盐混合的原始母岩浆液态不混熔的产物。 岩墙群形成的地质条件和构造背景表明,它们是在伸展构造背景下,受到不同级别的构造控制,大同岩墙群的研究对进一步认识华北早中生代岩石圈演化有重要的意义。     

河南商城—固始地区石炭系沉积环境及其构造意义

根据沉积相分析,同时综合分析区域地质资料,笔者提出河南商城－固始地区石炭系及安徽金寨地区梅山群为典型前陆磨拉石含煤建造,其沉积相主要为滨海、潮坪、泻湖、局限台地及砾质辫状河－冲积扇相,代表了统一的石炭纪一二叠纪合肥弧后前陆盆地的南部边缘相,说明大别地块（北大别弧）于早古生代晚期－晚古生代早期即与华北板块碰扪结成一体。     

华南早古生代陆内造山演化

华南早古生代造山带的构造属性长期缺乏统一的定论,且此次构造事件的形成机制与动力学背景研究较少。本文在前人研究成果的基础上,综合沉积环境、岩浆作用与岩浆来源、构造变形以及变质作用等地质证据,再次审视华南早古生代的构造演化过程。研究表明：1）华南广泛发育泥盆系与下伏前泥盆纪地层之间的角度不整合面,早古生代沉积相自江南区到华夏区呈过渡渐变,无同期火山碎屑岩、含鲍马序列的浊积岩等洋盆相关的记录;2）华南出露大规模弥散型面状分布的S型花岗岩,结晶年龄集中于443～423 Ma,在任何方向均无新老演化趋势,且岩浆主要来自壳源物质的熔融再循环,几乎无幔源物质加入;3）华南早古生代以低绿片岩相变质作用为主,仅陈蔡、龙游等地区零星出露绿片岩相—麻粒岩相变质岩;变质时间与岩浆结晶年龄相近,变质P-T-t轨迹均为近等温降压的顺时针轨迹;4）华南早古生代绝大部分构造线为近S-N与NE方向,变形作用以韧性流变为主,以武夷山瑞金—遂昌为轴呈双向逆冲推覆构造模式。根据以上地质事实,本文推断华南早古生代构造事件属性为陆内造山,即华南板块边缘汇聚碰撞产生的应力,经岩石圈远距离传播至大陆内部的远程响应。     

从岩相古地理论塔里木盆地西南地区石炭系油气潜景

石岩系是塔里木盆地西南地区重要的海相烃源岩和储集岩地层，油气潜力很大，但目前仅发现了1个气田、1个油田和2个油藏，勘探程度很低。本文在岩相古地理和地震地层学岩性岩相研究的基础上，对本区石炭系的烃源岩和储集岩的类型、分布及其与沉积环境的关系进行了研究，对盖层性质和分布，尤其对石炭系经过多次大的构造变动后所形成的油气潜景区进行了较深入的探讨，并指出4个有利的油气勘探地区，即巴楚隆起西端、玛扎塔克断裂带-海米-罗斯断裂带、麦盖提斜坡的北缘、南缘推覆体上盘。同时指出了各有利地区的勘探对策。     

U-Pb-Hf isotopic data from detrital zircons in late Carboniferous and Mid-Late Triassic sandstones,and also Carboniferous granites from the Tauride and Anatolide continental units in S Turkey: implications for Tethyan palaeogeography

ABSTRACT

Zircons from Carboniferous sandstones (three samples) and Mid-Late Triassic sandstones (four samples) from the Tauride and Anatolide continental units were analysed for U-Pb-Hf isotopes. For comparison, zircons were also analysed from Carboniferous granites of the Afyon Zone, Anatolides (three samples). A NE African/Arabian source is inferred for both the Carboniferous sandstones of the Taurides (Alada?) and the Anatolides (Konya Complex). In contrast, the Carboniferous Karaburun Melange is characterised by a NW African provenance. A prominent Devonian population occurs in the Carboniferous Karaburun Melange, characterised by mainly positive ε_Hf(t) values that differ significantly from those of the Devonian granites of the Sakarya continental crustal unit (Pontides). Middle-Late Triassic Tauride sandstones include minor Palaeozoic and Early Mesozoic zircons. In contrast, Devonian and Carboniferous zircons are relatively abundant in Late Triassic sandstones of the Karaburun Peninsula. The Hf isotopic compositions of 25 Carboniferous-aged zircons from three samples of Mid-Late Triassic sandstone and one of Late Carboniferous age (one sample) overlap with the ε_Hf(t) values of Carboniferous arc-type granites in the Anatolides. Taking account of the available U-Pb and Lu-Hf isotopic data from comparative crustal units, the Devonian zircon populations from the melanges in the Karaburun Peninsula and the Konya Complex are inferred to have a westerly source (e.g. granitic rocks of Aegean region or central Europe). A tectonic model is proposed in which Palaeozoic Tethys sutured during the late Carboniferous in the west (Aegean region westwards), leaving an eastward-widening oceanic gulf in which sandstone turbidites accumulated, including Devonian zircons.     

Early cretaceous granitoids and their implications for the collapse of the Dabie orogen, eastern China: SHRIMP zircon U–Pb dating and geochemistry

Two stages of early Cretaceous post-orogenic granitoids are recognized in the Dabie orogen, eastern China, which recorded processes of extensional collapse of the orogen. The early stage granitoids ( 132 Ma) are foliated hornblende quartz monzonites and porphyritic monzogranites. They are of high-K calc-alkaline series and metaluminous to weakly peraluminous, with high K₂O and low MgO contents (Mg^# values: 32.0–46.0), they contain high Sr, low Y and heavy rare earth elements (HREE), and have high Sr/Y and (La/Yb)_N ratios, without clear negative Eu, Sr and Ti anomalies. The early stage deformed granitoids have adakitic geochemical compositions and are equilibrated with residues rich in garnet and poor in anorthite-rich plagioclase, and thus indicate the existence of an over-thickened (> 50 km) crustal root beneath the orogen at  132 Ma. The later stage granitoids ( 128 Ma) are undeformed fine-grained monzogranites, fine-grained K-feldspar granites and coarse-grained K-feldspar granite-porphyry. They belong to a peraluminous and high-K calc-alkaline to shoshonite series, and display a flat HREE pattern and have strong negative Eu, Sr and Ti anomalies, with low Sr/Y and (La/Yb)_N ratios. The late stage granitoids are equilibrated with residues rich in anorthite-rich plagioclase, hornblende, ilmenite/titanite and poor in garnet, indicating that the crust of the Dabie orogen became thinner (< 35 km) at  128 Ma. SHRIMP zircon U–Pb ages and changing compositional trends for these two stages of granitoids indicate that the over-thickened crust formed by the Triassic continental subduction/collision under the Dabie orogen remained until the early Cretaceous, and collapsed quickly in a few million years during the early Cretaceous.