浙江长兴煤山地区吴家坪阶-长兴阶界线地层的再认识

浙江长兴煤山的 D剖面经多年研究 ,已成为二叠系长兴阶的单位层型和二叠系 -三叠系全球界线层型 ,并被推荐为吴家坪阶 -长兴阶全球界线层型的候选剖面 ,因该剖面上龙潭组地层出露较少 ,以致国内对长兴组与龙潭组的接触关系存有不同意见 ,给层型剖面的建立带来不利影响。在清理和研究了 D剖面西侧 30 0 m处 C剖面的吴家坪阶 -长兴阶界线层段后 ,证实了煤山地区龙潭组与长兴组为整合接触 ,对相关化石的地层分布也获得进一步的认识     

福建的长兴阶

福建长兴期地层发育,包括碎屑岩相的大隆组和灰岩相的长兴组,长兴组分布于大田及其与永安、漳平交界处,大隆组主要分布于闽西南地区。根据生物群特征,建立了全省长兴阶7个生物带,并和华南地区长兴阶生物群作了对比。论证了福建长兴阶底界应划在大隆组下部,以Oldhamina squamosa 为代表的含海相腕足化石层下部砂岩之底。省内通常划归翠屏山组第四段的海相层应划归长兴阶。福建的长兴组含长兴阶上部生物群,其下含长兴阶下部生物群,福建长若灰岩应为长兴阶上部,大致为大隆组中上部的相变,其所含 Palaeofusulina sinensis带相当于大隆组上部 Pseudotirolites-Pleuronodoceras 带。     

长兴阶名考

长兴阶是由中国命名的第一个被列入国际地质年表的阶名，现在其顶底界线定义及界线层型都已确定。但有关长兴阶命名的历史说法不一。     

贵州安顺长兴阶顶部三叶虫化石

三叶虫是二叠纪末生物集群灭绝中消失的生物门类之一,但是关于该门类生物化石在中国消失的确切层位未见报道。贵州安顺新民剖面大隆组顶部的三叶虫化石Pseudophillipsia sp.产于火山成因的黏土岩之炭质泥岩夹层中,相邻的泥灰岩结核中产牙形石化石Clarkina meishanensis。该黏土岩及炭质泥岩夹层可以与浙江长兴煤山D剖面的第25层对比,这说明三叶虫延续到了主灭绝事件层位,对研究二叠纪末生物集群灭绝的原因具有一定的意义。     

湖南郴县红旗岭锡多金属矿床地质特征及成因

红旗岭锡多金属矿床位于东坡矿田北东角,是千里山花岗岩岩体北侧的一个重要的矿床。该矿床赋存于震旦系下组浅变质砂岩中,受断裂裂隙控制,品位富,探明储量达6.3万t,属裂隙充填型(大型)高—中温热液矿床。     

Gallowayinella的时代——兼论长兴阶与吴家坪阶的分界

<正> 陈旭教授1934年建立Gallowayinella属,是纪念美国有孔虫学者Galloway的。初发表时称为Gallowaiina,1937年被Dunbar和Skinner改为Gallowaiinella。1964年,Thompson指出这两个属名的拼法都有缺陷,把Galloway的最后一个字母变成“i”,与国际动物命名法32条a(ii)和c的规定不符,应予改正。但如果机械地改成Gallowayina,则此名又早在1932年被有孔虫圆片虫类(orbitoid)的Gallowayina Ellis所占用。因此,Thompson(1964)将其改成Gallowayinella,并认为符合国际动物命名法56条a的规定的。     

华南二叠系长兴阶灰岩的碳同位素地层对比

以浙江长兴煤山长兴阶层型剖面、江西上高七宝山剖面、陕西汉中梁山剖面为代表的华南长兴阶碳酸盐岩碳同位素地层,清楚地显示出长兴阶顶、底为碳同位素低值区,其中Ｐ－Ｔ界线附近的碳同位素出现强烈负异常事件。在长兴阶内部两次碳同位素低值异常区,将长兴阶碳同位素演化曲线由下至上明显分为３个旋回,其中长兴阶顶,也即Ｐ－Ｔ界线,碳同位素强烈负异常与生物绝灭事件有关,时间短,变化幅度大,是全球界线对比的重要标志。而其它碳同位素负漂移和由此构成的３个旋回,在华南可以追踪对比。上旋回与长兴阶上段煤山段相当;而中、下旋回则与下段葆青段相当,并将其两分。碳同位素地层对比表明江西上高地区长兴组的中、上部可能属长兴阶,而下部厚约９０ｍ的含Ｇａｌｏｗａｙｉｎｅｌａ灰岩可能属吴家坪晚期。     

浙江长兴地区长兴组放射虫化石及其指相意义

浙江省长兴地区的长兴组煤山剖面一直作为中国乃至世界研究二叠系-三叠系界线的经典剖面之一。在该剖面,长兴组主要由灰黑、黑色碳酸盐组成,厚度约为30-45m。依据沉积岩性特征大致可划分上下2段:下段以灰黑或黑色的纹层状粒泥岩和泥粒岩为主,厚度约13m;上段由薄一中层状灰黑或黑色泥粒岩和粒泥岩组成,其中夹有极薄层的黑色钙质泥岩或泥岩和细条带状或透镜状硅质岩,厚27m左右。     

湖南郴县红旗岭锡多金属矿床的成矿时代应为燕山早期

载于《云南地质》1984年第l期(总9期)的“我国锡矿的成矿地质特征及成矿远景区划浅析”一文,在阐述我国锡矿成矿时代的多期性时,把湖南省郴县红旗岭锡多金属矿床作为燕山晚期成矿期的一个实例,笔者认为不妥,说明如下: 与红旗岭锡多金属矿床有成因关系的千里山花岗岩体是个复式岩体,位于红旗岭矿区的西南缘,岩体呈岩株产出,出露面积9.5平方公里,侵入下限为D_8s。主体花岗岩同位素年龄测定值为1.72和1.39亿年(黑云母),湖南地质408队将其归入燕山早期第一阶段(γ_5~(2-1)),湖南地质科研所将其归入燕山早期第二阶段(γ_5~(2-2))。1982年11月《湖南地质科技情报》第6期刊登的“对     

湖南郴县野鸡尾锡多金属矿床地质特征及成矿规律

野鸡尾锡多金属矿床位于千里山花岗岩东南接触带外部,产于浅部石英斑岩相岩枝及与其侵入的中泥盆统棋梓桥组白云质灰岩中。已探明主矿体3个,分别为石英斑岩型、矽卡岩型、网脉大理岩型,属大型锡多金属矿床。     

The Changhsingian small foraminifers from the Gyanyima section in southern Tibet, China

The Gyanyima section is located in the Himala-yan Tethys Zone, just south of the Indus-Tsangbo su-ture. The Permian part of the section is made up of grayish to reddish white reefal limestone that yields rich warm-water faunas of Changhsingian age. We recently found highly diversified smaller foraminifers dominated by Colaniella parva in association with the genera Pachyphloia, Frondina, Nodosaria, Robuloides, Geinitzina, Tetrataxis, Tuberitina, Abadehella, Cli-macammina, Dagmarita, Postendothyra, Neoendo-thyra, Globivalvulina, Paraglobivalvulina, Agatham-mina, Multidiscus, and Kamurana. In comparison, fusulinoideans are a minor element of the fauna and include Nankinella, Staffella, Reichelina pulchra, and Codonofusiella?. In addition to these fusulinoideans, a new boultoniid genus is found in the upper part of the section. This form shares some similarities with Codonofusiella and Parananlingella in its un-coiling or loose-coiling tendency in the last volution, but it is distinct from these two boultoniid genera in having a rapidly expanding but fully coiled last half volution.     

The Changhsingian Foraminiferal Fauna of the Meishan D Section,Zhejiang, China,and their Ecostratigraphic Implications

Samples were collected continuously and systematically from Beds 2 to 30 of the Meishan D section, and nearly 4,000 foraminiferal specimens were recognized. In total, 72 species (partially including undetermined species and conformis species) in 34 genera of foraminifers were identified. Twelve foraminiferal community zones were established from Beds 2 to 27 based on the abundance, dominance, diversity, and equitability of the foraminiferal fauna and a functional morphological analysis of the dominant and characteristic species. The habitat type indicated by each community zone and the sedimentary features were used to determine the paleo‐water depths and the relative changes in sea level. We generated curves of both the habitat type and the hydrodynamic conditions, which together indicate the relative changes in the paleo‐water depth and the substrate features in the studied area during the Changhsingian. This study discusses the possible relationship between the foraminiferal community zones and the sea‐level changes based on a statistical analysis of the foraminiferal community zones.     

甘肃成县庙沟铅锌矿成矿环境及控矿构造分析

甘肃成县庙沟铅锌矿床位于秦岭造山带西部,西(和)-成(县)铅锌矿田东段,矿床类型属喷流沉积型。岩石、矿石微量元素特征表明矿区形成时为贫氧环境;稀土元素Eu异常特征反映矿区古成矿流体温度较低,与厂坝-李家沟铅锌矿床形成条件相似; Ce异常特征亦反映矿区形成于贫氧的还原环境。通过探矿工程揭露,认为银洞湾矿段受其北东侧断层(F)与南西侧陡倾矿体共同控制,构造挤压是矿区形成高品位矿石的主要原因。结合区域上的研究成果,建立了矿区成矿模式,指出矿区应注意寻找块状、网脉状矿体,赋存于标高1700～1500m空间内的矿体,以及被断层(F)断失的矿体。     

Research on Ecostratigraphy of Changhsingian at Meishan Section D, Changxing, Zhejiang Province

On the basis of researches over several years on biostratigraphy of Changhsingian at Meishan Section D in Changxing County, the abundant materials were accumulated. This paper studies the escostratigraphy and establishes 7 community zones (CZ), in ascending order, Sinoplatysomus-Gernitzina-Clarkina subcarinata, Tapashanites-Nodosaria-Clarkina subcarinata,Crurithyris-Geinitzina-Clarkina subcarinata,Glomospira-Clarkina changxingensis, Colaniella-Clarkina changxingensis,Rotodiscoceras-Palaeofusulina-Hindeodus typicalis,Clarkina meishanensis-Hypophiceras.The habitat type (HT) is diffent from upper shallow sea to the lower part of the lower shallow sea.     

重庆巫溪红池坝长兴阶深水相沉积记录及地质意义*

重庆巫溪红池坝剖面长兴阶上部地层出露齐全,产系列牙形刺和深水陆棚相遗迹化石。通过建立牙形刺带,对该剖面长兴阶沉积相类型及特征进行了精细研究,并讨论了区域大隆组/长兴组界线的时代归属。长兴中—晚期开始,沉积环境由深水盆地向深水陆棚逐渐过渡,海洋生态环境的不稳定性开始显现并持续发展,基于时间序列的遗迹化石记录详细刻画了深水陆棚水体含氧量频繁加速波动过程,为系统审视二叠纪末生物与环境协同演化提供了重要依据。     

Fe-rich Li-bearing magnesionigerite-6N6S from Xianghualing tin-polymetallic orefield, Hunan Province, P.R. China

The Fe-rich Li-bearing magnesionigerite-6N6S occurs in the Xianghualing tin-polymetallic ore field, Linwu County, Hunan Province, Peoples Republic of China. It was found near the outer contact zone of the Laizhiling granite body and in the Middle-Upper Devonian carbonate rocks of Qiziqiao Formation. The mineral formed during the skarn stage. Its empirical formula is Sn_1.81Li_0.67(Fe_1.43Zn_1.19 Mn_0.41)_Σ3.03(Al_14.89Mg_1.46 Ti_0.11Si_0.01)_Σ16.47O₃₀(OH)₂. The structure for magnesionigerite-6N6S was solved and refined in space group R-3?m, with a?=?5.7144(8), c?=?55.446(11) Å, V?=?1568.0(4) ų, to R1?=?0.0528. Based on the structural refinement of single crystal diffraction data the formula of magnesionigerite-6N6S is Sn_1.80Li_0.97(Fe_1.89Zn_0.91) _Σ2.80 (Al_14.60Mg_1.63 Ti_0.20)_Σ16.43O₃₀(OH)₂ with Z?=?3. Fe-rich Li-bearing magnesionigerite-6N6S contains 0.74 wt.% Li₂O. The idealized charge-balanced composition of magnesionigerite-6N6S may be expressed by bivalent and trivalent cations: (Mg²⁺)₄(Al³⁺)₁₈O₃₀(OH)₂. The simplified general formula for the 6N6S polysomes in the nigerite and högbomite groups can be given as A _x B_18-x O₃₀(OH)₂, x?=?~4, where A?=?Mg²⁺, Fe²⁺, Zn²⁺; B?=?Al³⁺, Sn⁴⁺, Ti⁴⁺, Li⁺, □.     

Upper Permian (Late Changhsingian) marine strata in Nan Province,northern Thailand

In the Upper Permian of northeastern Thailand (Loei Province), continental plants have been found and to the north in Laos near Luang Prabang, continental vertebrates (Dicynodon species) have been discovered. The Middle Permian is in sharp contrast to this as it is represented only by marine sediments. West of these areas in the province of Nan in Thailand, the Upper Permian is represented by marine sediments which extend to a high level in the Upper Permian and continental beds appear to be entirely absent, at least at Pha Dang Khwai, a locality where limestone extends from the end of the Lower Permian to the Triassic.     

The Wuchiapingian–Changhsingian boundary (Upper Permian) at Meishan of Changxing County, South China

Section D at Meishan, Changxing County in the Zhejiang Province, China, has been extensively studied in various aspects of the stratigraphy during the past 20 years. It was ratified by the International Union of Geological Sciences (IUGS) as the Global Standard Stratotype Section and Point (GSSP) for the Permian–Triassic boundary in 2000, and is also a potential stratotype for the Wuchiapingian–Changhsingian boundary. However, the contact relationship between the Longtan (Wuchiapingian) and Changxing (Chainghsingian) formations has been a controversial subject for years. Recent studies on Section C, about 300 m west of Section D, at Meishan confirm a complete depositional succession around the boundary and suggest that the proposed boundary level, the FAD of Clarkina wangi within the lineage from C. longicuspidata to C. wangi, is consistent with the first appearance of the index Changhsingian fusulinid Palaeofusulina sinensis and tapashanitid ammonoids.