河南西部“山西组”含大羽羊齿植物的层位

<正> 大羽羊齿类植物是二叠纪华夏植物群的典型代表,它们的始现时间一直是地质古生物工作者所关注的问题。近年来,不断有关于华北山西组中发现大羽羊齿类植物化石的报道,但由于对山西组的含义认识不同,或者没有图片佐证,因而大多对此持保留态度。本文以河南西部(图1)几个“山西组”剖面中产大羽羊齿类植物化石的层位为例,讨论一     

贵州西部晚二叠世大羽羊齿类植物的生态

根据大羽羊齿伴生植物群、叶相、生活型、钩状物、表皮、气孔、叶子解剖、分泌结构、保存环境等多方面的研究,认为本区大羽羊齿类植物为热带一亚热带季雨林植物。但大羽羊齿类不是本区的主要成煤植物。      

甘肃永昌乌拉尔世Sphenopteris(楔羊齿)新记录: 兼论晚古生代Sphenopteris多样性及古地理演化*

Sphenopteris(楔羊齿属)叶化石在全球晚古生代地层中广泛出现,但该属的系统分类位置及演化特征仍有待深入探讨,而且只有极少数种的表皮及气孔微细构造得到揭示。笔者在甘肃永昌乌拉尔统山西组中发现了2种形态保存较好且具有角质层的楔羊齿,分别是 Sphenopteris yongchangensis sp. nov.(永昌楔羊齿—新种)和Sphenopteris nystroemii (弱楔羊齿)。前者小羽片呈扇形,基部连合,侧脉分叉1次,气孔作椭圆状且为两面生; 后者小羽片呈梭形且顶端钝圆,侧脉分叉1次并达缘,气孔分布于脉间区。经对比,文中报道的2种楔羊齿可能属皱羊齿目(Lyginopteridales)。此外,统计了Sphenopteris在晚古生代的269个化石记录,结合该属的形态学、解剖学特征和分布记录,探讨了其多样性演化和古地理分布,结果表明: 宾夕法尼亚亚纪至乌拉尔世,Sphenopteris广泛分布于全球中低纬度地区,呈现出高度变异和分化; 自晚泥盆世至二叠纪,Sphenopteris型叶化石在中国自华南向华北迁移演化,说明其多样性特征不仅与湿润气候密切相关,而且与其古地理分布相耦合。     

中国晚泥盆世至早三叠世楔叶类植物多样性研究

化石类群的分类单元多样性和形态多样性变化是生物宏演化的 2 个基本方面,而以往的研究对于后者的关注较少.晚古生代的楔叶类植物易于识别,化石记录丰富,但针对这一类群多样性演化的研究还较为缺乏.基于华北板块、华南板块晚泥盆世至早三叠世楔叶类植物属、种以及叶片形态编码数据库,对楔叶类植物宏演化历程进行详细研究.中国(华北板块...     

北祁连山东段晚石炭世巴什基尔期植物群 ——兼论华夏植物群起源中心

北祁连山东段纳缪尔晚期(相当于巴什基尔期)植物群,共33属95种植物,其中地方性的土著分子(属、种)占有整个植物群总数的80%以上,华夏植物群(Cathaysia Flora)的典型特征分子较多,如①东方型鳞木类占植物群总数的25%左右,包括从早石炭世延续下来的华夏木(Cathaysiodendron)、多种东方型鳞木(Lepidodendron)、窝木(Bothrodendron)及扁圆封印木(Sigillaria brardii);②由晚泥盆世开始出现的龙潭楔叶(Sphenophyllum lungtanense)、长沙楔叶?(Sphenophyllum?(Tetrafolia)changshaense)、早石炭世的靖远楔叶(Sphenophyllum jingyuanense)到纳缪尔晚期的微缺楔叶(Sphenophyllum emarginatum),这类具有长楔形叶的植物出现得比欧美地区早许多,可能是二叠纪瓣轮叶(Lobatannularia)的最早祖先;③齿叶属(Tingia)在早石炭世晚期已经出现,到纳缪尔晚期(红土洼组)已有三种之多,加上贝叶属(Conchophyllum),这两属一直被认为是华夏植物群的典型代表;④多种早石炭世中、晚期繁盛的真蕨类植物偶脉羊齿(Paripteris)及网羊齿(Linopteris)到晚石炭世早、中期仍十分发育,是华夏植物群早期最显著的特征;⑤早石炭世的畸羊齿(Mariopteris(Karinopteris))继续发育,而后可能演化成大羽羊齿类植物(Gigantopterids)的先祖。本文通过对比研究证实,北祁连山东段的纳缪尔晚期植物群已经进入华夏植物群的早期演化阶段;自从晚泥盆世的沙流水组开始,先后经历了早石炭世的臭牛沟组,靖远组及晚石炭世红土洼组和羊虎沟组(本溪组)代表了前华夏植物群(Procathaysian Flora)演替为华夏植物群的关键地质时期。北祁连山东段亦成为前华夏植物群和华夏植物群早期发育、繁盛之地区,在纳缪尔期可能是华夏植物群的起源和早期演化中心。     

大羽羊齿煤系研究的进展

最近,湖南公司一队程正修和中科院植物研究所朱家楠、胡雨帆合作完成了“湘南早二叠世晚期泥巴口植物群”课题的研究工作。根据永兴泥巴口实测地层剖面及常宁斗岭、盐湖和白沙向斜、永耒向斜、石里山向斜各煤产地采集的大量化石的鉴定,共计有22属39种,其中新种1个,新组合、国内新记载和新模式种各1个。对斗岭煤系的成煤植物系统分类、各属种比例提供了基础资料。同时,对单网羊齿叶片上附生的龙介类螺旋虫也作了描述与生态研究。值得一提的是烟叶大羽羊齿这种化石,1883年,Schcnk根据1870年Richthofen采自中国     

中国晚泥盆世至早三叠世楔叶类植物多样性研究*

化石类群的分类单元多样性和形态多样性变化是生物宏演化的2个基本方面,而以往的研究对于后者的关注较少。晚古生代的楔叶类植物易于识别,化石记录丰富,但针对这一类群多样性演化的研究还较为缺乏。基于华北板块、华南板块晚泥盆世至早三叠世楔叶类植物属、种以及叶片形态编码数据库,对楔叶类植物宏演化历程进行详细研究。中国(华北板块和华南板块)楔叶类植物的属、种丰富度在晚古生代呈现出不稳定的持续增长,表现为晚泥盆世的初始兴盛、早石炭世杜内期至早二叠世萨克马尔期的缓慢上升、早二叠世萨克马尔期至晚二叠世吴家坪期的快速上升;晚二叠世长兴期,总体的属种多样性骤减;每百万年属种多样性在二叠纪—三叠纪之交亦有明显降低。华南板块楔叶类植物的属种多样性总体上小于华北板块,达到峰值的时间为卡匹敦期—吴家坪期,而华北楔叶类植物的属级多样性在空谷期—沃德期达到峰值。中国楔叶类植物叶片的形态多样性的剧烈变化与属种丰富度并不同步,表现为法门期至韦宪期较小,在宾夕法尼亚亚纪达到峰值,随后稍微下降并在二叠纪的大部分时段保持平稳。在晚古生代的叶片形态演化过程中,楔叶类植物的叶面积由小变大、叶片由深裂至不裂、叶尖形状由分裂变为圆形或钝圆、叶轮中的叶从大小相等到大小不等并出现叶镶嵌,这可能与当时植物群落中林下层光照强度的变化有关。     

黔南上二叠统大隆组海相地层中的植物化石研究

贵州安顺新民剖面大隆组海相地层产出一批丰富的植物化石,以裸子植物和带羊齿类为主要成分,另有石松纲、楔叶纲、真蕨纲和种子蕨纲,与国内外同期植物群对比发现,华南、华北和欧美地区植物群同反映出晚二叠世末松柏类进入繁盛期,属级成分的差异应为生态气候所致,新民植物群生活型可分为两个基本层次,局部的高地生长着松柏类等旱生群落,湿水沼泽旁乔木、小乔木、树蕨和灌木植物发育,对其反映的气候信息分析表明,华南晚二叠世已不及之前的湿热,为早三叠世干旱的气候类型埋下伏笔。     

论华南地区二叠纪成煤期

长期以来,我国华南地区二叠纪的成煤时代,一般认为只有早三叠世早期的梁山期和晚二叠世早期的龙潭期。后者以含大羽羊齿植物群为特征,所以又常被称为“大羽羊齿煤系”。近年来,随着区调和煤田地质工作的深入开展,华南二叠系研究获得了新的进展,证明了“大羽羊齿煤系”实际上包含了二叠纪不同时期的含煤地层,尤其是华南地区具有工业价值的煤层,并不限于赋存在上述两个含煤地层中。因此,不同成煤期的正确划分,将     

华北板块大羽羊齿植物的成煤古气候含义

华北板块存在3个大羽羊齿分布区:Ⅰ—大羽羊齿植物贫乏区;Ⅱ—Gigantonoclea分布区;Ⅲ—Gigantonoclea—Gigantopteris共存分布区。根据大羽羊齿植物的地理限制、叶相特征和其他标志重建了华北板块早二叠世晚期至晚二叠世早期的古气候分带格局:其东南部（Ⅲ区）处于无季节性分化的热带雨林气候,并逐渐向西北过渡为萨旺纳气候（Ⅱ区）和热带草原气候（Ⅰ区）。上述古气候分带的现今取位方向（北东向）是华北板块于二叠纪的北向漂移过程中,伴随35°～45°逆时针旋转造成的。正是这种运动机制,使得华北板块逐渐脱离赤道附近的热带雨林成煤气候带,导致早二叠世早期广泛存在的聚煤作用,在早二叠世晚期—晚二叠世早期收缩至现今华北地台的东南一隅。      

细茎苏铁植物—新属Cathaysiocycas及其演化意义

新属Cathaysicycas产自河南禹县早二叠世早期神垕组(“山西组”)的中部。该属具Taeniopteris型叶,松散螺旋状着生于较光滑的细轴上。大孢子叶的中上部全部深裂成线形裂片,种子着生于线形细裂片之顶端。Cathaysiocycas线形裂片顶端着生种子的形式可视为自Spermopterist种子着生于叶边缘的类型进一步演化的阶段,并由此而进化为中生代Beania状的复合种子的形式。     

藏南舌羊齿植物群的发现和其在地质学及古地理学上的意义

喜马拉雅地区一直被传统地质学认为是一个典型的古地槽区,属于劳亚和冈瓦纳两古大陆之间的古地中海的一部分,具有很厚的古生代到老第三纪的海相沉积。本世纪上叶,魏格纳就提出大陆漂移的假说,设想陆块之间曾有过大规模的水平移动,可是大陆固定和海洋永存的传统观念在人们脑海中根深蒂固。     

豫西—皖北地区二叠纪植物地理区系性质探讨

基于对豫西－皖北地区和华北、华南二叠纪植物化石分布状况的全面对比统计,简略分析了豫西－皖北地区二叠纪植物群演替,将该区各阶期与华北及华南同期植物群进行了工对其间Simpson相似性系数作了求算。结果表明它应作为华夏植物各华北植物区内的一个次级植物地理单元对待其成因与华北、华南二叠纪时古板块的旋转、漂移、聚散等行为及其特定的古地理条件密切相关。     

Characteristics of Triassic epithermal Au mineralization at the Q prospect,Chatree mining area,Central Thailand

The Chatree deposit is located in the Loei‐Phetchabun‐Nakhon Nayok volcanic belt that extends from Laos in the north through central and eastern Thailand into Cambodia. Gold‐bearing quartz veins at the Q prospect of the Chatree deposit are hosted within polymictic andesitic breccia and volcanic sedimentary breccia. The orebodies of the Chatree deposit consist of veins, veinlets and stockwork. Gold‐bearing quartz veins are composed mainly of quartz, calcite and illite with small amounts of adularia, chlorite and sulfide minerals. The gold‐bearing quartz veins were divided into five stages based on the cross‐cutting relationship and mineral assemblage. Intense gold mineralization occurred in Stages I and IV. The mineral assemblage of Stages I and IV is characterized by quartz–calcite–illite–laumontite–adularia–chlorite–sulfide minerals and electrum. Quartz textures of Stages I and IV are also characterized by microcrystalline and flamboyant textures, respectively. Coexistence of laumontite, illite and chlorite in the gold‐bearing quartz vein of Stage IV suggests that the gold‐bearing quartz veins were formed at approximately 200°C. The flamboyant and brecciated textures of the gold‐bearing quartz vein of Stage IV suggest that gold precipitated with silica minerals from a hydrothermal solution that was supersaturated by boiling. The δ¹⁸O values of quartz in Stages I to V range from +10.4 to +11.6‰ except for the δ¹⁸O value of quartz in Stage IV (+15.0‰). The increase in δ¹⁸O values of quartz at Stage IV is explained by boiling. P_H2O is estimated to be 16 bars at 200°C. The f_CO2 value is estimated to be 1 bar based on the presence of calcite in the mineral assemblage of Stage IV. The total pressure of the hydrothermal solution is approximately 20 bars at 200°C, suggesting that the gold‐bearing quartz veins of the Q prospect formed about 200 m below the paleosurface.     

吉林延边地区下白垩统长财组铁角蕨属一新种

现生铁角蕨Asplenium Linn.种类繁多,广布于热带—温带地区,以热带—亚热带为分布中心。确切的Asplenium Linn.化石最早出现于东亚和俄罗斯远东地区的下白垩统地层中,是西伯利亚—加拿大区白垩纪的新生分子。根据吉林延边地区下白垩统长财组发现的铁角蕨化石的营养羽片和生殖羽片标本,在原位孢子研究基础上,通过与现生铁角蕨植物繁殖器官的对比,确认当前材料属于Asplenium Linn.;并进一步与国内外相关属种进行比对,建立了一个新种——长财铁角蕨（新种）（Asplenium changcaium Sun et Liu, sp. nov.）。该新种原位孢子的研究为深入探讨铁角蕨属乃至铁角蕨科的系统演化奠定了基础。     

A Preliminary Study on Skarn-Related Calc-silicate Rocks Associated with the Batu Hijau Porphyry Copper-Gold Deposit, Sumbawa Island, Indonesia

Batu Hijau is a world-class gold-rich porphyry copper deposit, situated in Sumbawa Island, Indonesia. Deep drilling indicates that several intervals of calc-silicate rock were intersected, where they are apparently interbedded with volcaniclastic rocks. The calc-silicate rocks occur at the contact with copper-gold-bearing tonalite porphyries. The rocks are fine-grained and granular with green, reddish-brown and white layers. The green layers consist mostly of fine-grained clinopyroxene (diopside and hedenbergite) and the reddish-brown layers consist mostly of garnet (andradite), whereas the white layers are commonly composed of calcite and zeolite (chabazite). The calc-silicate rocks were formed by contact metasomatism of andesitic volcaniclastic rocks, as it is calcic in composition. Paragenesis study reveals at least two stages of calc-silicate mineralization. Stage 1 (prograde) is characterized by the presence of garnet (andradite), clinopyroxene (diopside and hedenbergite), anorthite and quartz at 340–360 C (high salinity 35–45 NaCl wt percentage eqn.). Stage 2 (retrograde) is characterized by chlorite and rare epidote at 280–300 C (low salinity 1–10 NaCl wt% eqn.). Late calcite ± quartz veinlets and calcite + chabazite veins/veinlets may also be related to this stage and cross cut the oldest mineral assemblages. Mineralization (magnetite, chalcopyrite and pyrite) may occur during the retrograde stage. Clinopyroxene and garnet were modified by Fe-rich hydrothermal fluid (oxidizing condition) indicated by increase of Fe from core to rim of both the cogenetic minerals. The presence of the calc-silicate rocks associated with massive magnetite-chalcopyrite-pyrite assemblage indicates the occurrence of calcic-exoskarn surrounding the Batu Hijau porphyry copper-gold deposit.     

Formation and compositional variation of phlogopites in the Horoman peridotite complex,Hokkaido, northern Japan: implications for origin and fractionation of metasomatic fluids in the upper mantle

Harzburgite and lherzolite tectonites from the Horoman peridotite complex, Hokkaido, northern Japan, contain variable amounts of secondary phlogopite and amphibole. Phlogopite-rich veinlets parallel to the foliation planes usually cut olivine-rich parts of the rocks; single-grained interstitial phlogopites are usually associated with orthopyroxene grains. Amphiboles are disseminated in rocks or sometimes occur in the phlogopite-rich veinlets. Within individual veinlets, phlogopites show extensive inter-grain variations in K/(K + Na) ratio (0.96–0.75), generally decreasing from the central (usually the thickest) part towards the marginal parts of veinlets. In contrast, Ti contents are nearly constant in Ti-poor veins or decrease slightly with decreasing K/(K + Na) in T-rich veins. Variation of Ti in phlogopites is very large (0.1–6.8 wt%) and is inversely correlated with Mg/(Mg + Fe^*) (Fe^*, total iron) atomic ratios, which vary from 0.96 to 0.88. Intra-vein variation of phlogopite chemistry (especially K/(K + Na) ratio) could be achieved by in situ fractional crystallization of trapped fluids; variation of Ti, however, cannot be explained by in situ fractionation of the fluids, indicating various Ti contents of the parent fluids. It is suggested that fluids responsible for the formation of the Horoman phlogopites and amphiboles were magmatic volatiles successively released from evolving alkali basaltic magmas. Individual fluids trapped within peridotites were fractionated, precipitating phlogopites successively poorer in K. When the fluids became rich enough in Na, amphiboles co-precipitated with phlogopites. Similar fractional crystallization of phlogopites and amphiboles is expected in the upper mantle on a larger scale if fluids move upwards. This process may control, at least partly, a lateral K/Na distribution in the upper mantle; K and Na may be concentrated in deeper and shallower parts, respectively.     

Gold deposits associated with the gabbroic rocks at Tirek area,western Hoggar,Algeria: fluid inclusion study

The Tirek gold deposit hosted in the Archean shield is one of the richest sources of mined gold for Algeria. The deposit is controlled by the East Ouzzal shear zone (EOSZ), a transcurrent N–S lithospheric fault. The EOSZ is a late Pan-African dextral-ductile shear zone separating two contrasting Precambrian domains: the Archean In Ouzzal block to the west (Orthogenesis with subordinate metasediments reworked and granulitized during the ca. 2 Ga Eburnean event) and a middle Proterozoic block to the east involved in the ca. 600 Ma Pan-African event. The auriferous quartz veins are mainly oriented in two directions, N–S veins hosted in mylonitic rocks and NE–SW veins hosted in gabbroic or gneissic bands. The NE–SW veins contain the richest ore. Gold ore is found in a system of veins and lenticular quartz veinlets arranged in anastomosing networks. The hydrothermal alteration associated with these veins is characteristically a carbonate-sericite-albite-pyrite assemblage. Gold is the main metal of economic importance; it is disseminated in the quartz as grains or fibers along microcracks and as microscopic grains in the host rocks. Microthermometric results and Raman laser data from fluid inclusions demonstrate that the ore-forming fluids contained H₂O-CO₂±CH₄ and were low salinity. Homogenization temperatures are commonly 250–310 °C. In the Tirek deposit, the role of the shear zone that hosts the mineralization was to drain the hydrothermal fluid. Interactions between the fluid and the mafic host rocks and CO₂ also contributed to the formation of the hydrothermal gold deposit at Tirek.     

吉林省小西南岔金铜矿床地球化学特征

小西南岔金铜矿床为浅成金铜共生大型矿床,受岩体-地层-构造联合控制,以叠加富集为主.矿区分为南山和北山两个矿段.矿化主要发育在闪长岩和斜长花岗岩中的北北西向断裂带及岩体接触带中,矿化以含金铜石英硫化物脉型及密集细脉为主.矿区水系沉积物异常元素为Au、Cu、Ag、Bi、Zn、Mo（W、Sb、As）;土壤异常元素为Cu、Mo、Au、Ag、Bi;岩石地球化学异常为Au、Cu、Ag、Bi、Ta、Ba、Sr（As、Sb、Zn、Co、Ni、W、Mo）.原生晕中轴向分带序列为（Bs、Sr）-As-Ag-Pb-Sn-W-Au-Bi-Cu-Sb-CoTe-Ni-Zn-Mo.南山矿段水平分带序列为Au-Cu-Bi-Te-Ag-Pb-Zn-As-Co-Ni-W-Sb-Mo-Sn;北山矿段为Au-Cu-Bi-Te-AgAs-Sb-Mo-Pb-Zn-Co-W-Ni-Sn.矿床地球化学异常特征及其分带性显示北山矿段矿体剥蚀程度大于南山矿段,矿区北西部矿体剥蚀强度大于南东部,表明向矿区南部仍有较大找矿远景.     

冀北水泉沟-后沟偏碱性侵入杂岩体的成矿特征

水泉沟-后沟偏碱性侵入杂岩体地处河北省崇礼-赤城地区,是我国唯一在碱性-偏碱性侵入杂岩体内发现许多具有工业意义金矿床的地区.偏碱性侵入杂岩体的展布受尚义-崇礼-赤城东西向深断裂控制,杂岩体主要由正长岩类、碱性正长岩类、二长岩类以及石英二长岩等岩石组成.综合岩石和矿床的常量元素、微量元素、稀土元素及铅同位素等特征,表明偏碱性侵入杂岩体是深部壳幔混合作用形成的;且金矿床的形成与偏碱性侵入杂岩体是密切相关的.成矿作用在偏碱性侵入杂岩体的东部与西部有所不同,西部多以石英脉、石英细脉、网脉型为主,围岩以正长岩、石英二长岩为主;东部则多为石英细网脉和破碎蚀变岩型,围岩主要是碱长正长岩、正长岩.金矿床受控于尚义-崇礼-赤城东西向深断裂的次一级东西向构造和南北向构造,赋矿部位主要在两组构造的交汇部位.