Diversity patterns of free‐living marine nematodes in the southwest continental shelf off Bay of Bengal and their link to abiotic variables

Marine sediments in continental shelf ecosystems harbor a rich biodiversity of benthic communities. In this study, the spatial and temporal diversity and community assemblages of free‐living marine nematodes were studied by sampling at six depths and over 3 years from the southwest continental shelf off Bay of Bengal, one of the least explored tropical shelf ecosystems. The dominant marine nematode species were related with abiotic variables as part of this study. The effects of sediment granulometry generally decreased with increasing depth and the highest nematode density and species diversity were recorded on coarse sand (shallower depths). Multivariate analysis of the nematode community data showed that community structure differed significantly among depths as well as among years. Statistical analyses showed significant correlations between the nematode community and abiotic variables. Sediment texture, organic matter, water pressure and depth profile were crucial factors for determining diversity, vertical profile and feeding types of the nematode community. Other environmental factors, including anthropogenic pressure, did not have an effect on nematode diversity except for the presence of some tolerant species (Metachromadora spp., Sabatieria spp. and Siplophorella sp.). This study represents a baseline of knowledge of free‐living marine nematode communities that can be used in the future to compare nematode assemblages from temperate shelf ecosystems.     

频谱分解技术在泥页岩储层含气性预测中的应用——以柴达木盆地鱼卡凹陷为例

针对柴达木盆地北缘鱼卡凹陷中侏罗统大煤沟组泥页岩,利用地震频谱曲线在不同流体介质储层中的形态、斜率、主频与中心频率的差值等属性参数特征,识别陆相泥页岩层系的地震频谱属性特征,预测含气性。研究结果表明,中侏罗统大煤沟组上部能量系数较低,平均为0.6719,下部能量系数较高,平均为0.7521,结合现场含气量和全烃特征认为,可以以能量系数0.7为界线,作为识别下部和上部含气性的标志,下部明显比上部含气性好。平面上进一步圈定了2个有利目标区,得到柴页1井勘探验证。因此,频谱分解技术可应用于中国陆相页岩气的勘查开发。     

Distribution and feeding modes of macrobenthos within three oceanographic feature areas of the KwaZulu-Natal Bight,South Africa

The composition and distribution of macrobenthic communities was investigated in three areas in the KwaZulu- Natal Bight, a section of shelf off the east coast of South Africa. Areas were pre-selected on the basis of three known oceanographic features, posited to deliver land- or Agulhas Current-derived nutrients onto the shelf and to drive ecosystem functioning in this region. Replicate sediment samples were collected with a 0.2 m² van Veen grab, during two surveys (A, B) corresponding with normal periods of high and low rainfall, respectively. A subset of the full station array was selected across the shelf in an arrangement of increasing depths (inner-, mid- and outer shelf) through each feature area to investigate the spatial distribution and feeding modes of macrobenthic taxa. The two periods showed some differences in abundance and numbers of macrobenthic taxa, but were not statistically different. Total macrobenthic abundance from Survey A was 20 215 individuals from 642 taxa, decreasing to 18 000 individuals from 503 taxa during Survey B. Polychaeta and Crustacea were the dominant taxa sampled; abundance of the latter was attributed largely to a proliferation of Paguristes sp.1 at inner-shelf samples in the midbight (Thukela) region during Survey B. Similarity classification distinguished seven sample groups reflecting differences in feature areas and shelf positions under investigation. The Thukela River midshelf community supported the highest macrobenthic abundance, while the midshelf off the southern bight (Durban region) was most species rich. Findings were attributed to the habitat complexity of the midshelf which includes a palaeo-dune cordon at the 60 m isobath. Functionally, the community was dominated by interface- and deposit-feeding fauna, emphasising the importance of trophic plasticity in an environmentally variable and heterogeneous shelf environment.     

陆相红层型铜铅锌矿床与红层盆地热卤水成矿作用

新疆乌恰县乌拉根超大型铅锌矿是中国发现的首个产于陆相红层盆地中的红层型铅锌矿床,对其成矿作用及成因有多种不同认识,但都将其归入现有的一些矿床类型,如喷流沉积型、砂岩型等,却均不能反映其独特的成矿环境与成矿作用。为此,在广泛收集和研究全国陆相红层盆地及其矿产的地质资料基础上,通过区域地质构造背景、含矿建造、矿床特征、控矿因素、成矿物质来源、成矿流体等方面对比分析,认为乌拉根铅锌矿与中国大量产于陆相盆地内红色建造中的红层铜矿,在矿床特征、控矿条件、矿床成因等方面具有高度的一致性,均为陆相红层盆地热卤水作用的结果,是同一类型的矿床。红层型矿床是地洼区的特有矿产,是地球地质演化到地洼阶段才出现的新的矿床类型,陆相红层盆地热卤水作用是一个完全独立的成矿系统,因此将其作为一个单独的矿床类型——红层型矿床是合理的,既具有重要理论意义,也具有重要的实践意义,为铅锌矿找矿开辟了新的方向和领域。     

对冀北-辽西-大兴安岭地区晚中生代地层划分、对比的区域构造学思考

根据冀北-辽西-大兴安岭地区晚中生代具有相关沉积建造组合、火山-沉积建造组合、生物组合和构造类型组合特征,提出建立与造山运动"同期"的构造地层单位概念.认为这种构造地层单位的概念有利于以区域构造演化为主线,理解"同造山期"陆缘活化区陆相沉积以及火山-沉积盆地地层系统的复杂性,并从区域构造学角度提出该地区地层划分、对比的方案.     

中亚陆间区南带上古生界构造和油气远景(代序)

安加拉-阿尔丹和华北-塔里木两大克拉通之间地壳相对活动性的地区,地质界多称为中亚陆间区,其南带大部分在中国境内。近年来,中国开始把其上古生界作为油气新区、新领域。多数人认为,其在晚古生代已形成过渡型地壳区,其中有许多地块已逐步拼合,在其上发育裂谷型沉积地质体,未受到区域变质,若干实体变形微弱并被上覆层掩盖而得到保存。源于上古生界的油气既可赋存在其内,也可运聚于中生界或基岩内,在其西段已发现了大中型油气田群。但其整体地质研究程度偏低,仍有许多重大区域地质、油气地质问题存在歧见。针对其近年来的进展、存在的问题和油气远景评价作了概括性的评论。     

Isotope stratigraphy and U-Pb dating of detrital zircons from the Vendian-Cambrian deposits of the North Muya block

U-Pb dating of detrital zircons from the sandstones of the Mamakan Formation has been made. Geochemical and isotope parameters of the carbonate deposits of the Yanguda Formation in the Vendian-Cambrian cover of the North Muya continental block have been estimated. It has been established that only the Neoproterozoic (630-915 Ma) rocks of the North Muya block were the provenances of terrigenous material. In the least altered carbonate rocks of the Yanguda Formation, the ⁸⁷Sr/⁸⁶Sr ratio is within 0.70814-0.70879 and δ¹³C varies from -0.4 to + 1.9‰. Comparison of the evaluated isotope parameters with those of carbonate rocks of typical Vendian-Cambrian sections shows that the carbonate deposits of the Yanguda Formation accumulated in the Early Cambrian, about 520 Ma. Sedimentation of the Mamakan and Yanguda Formations took place in the local sedimentary basin in the Vendian-Early Cambrian, in the absence of tectonic activity within the North Muya block. Detrital material that formed during the destruction of the rocks of the Siberian Platform basement and cover was not supplied into the basin.     

Isotopic-geochemical evidence for crustal contamination of eclogites in the Kokchetav subduction-collision zone

This paper reports isotopic and geochemical studies of eclogites from the western ultrahigh pressure (UHP) and eastern high-pressure (HP) blocks of the Kokchetav subduction-collision zone. These HP and UHP eclogites exhumed in two stages: (1) The rocks of the western block metamorphosed within the field of diamond stability (e.g., Kumdy-Kol and Barchy); (2) In contrast, the metamorphic evolution of the eastern block reached the pressure peak within the stability field of coesite (e.g., Kulet, Chaglinka, Sulu-Tyube, Daulet, and Borovoe). The eclogites vary widely in the ratios of incompatible elements and in the isotope ratios of Nd (¹⁴³Nd/¹⁴⁴Nd = 0.51137-0.513180) and Sr (⁸⁷Sr/⁸⁶Sr = 0.703930.78447). The Sulu-Tyube eclogites display isotope-geochemical features close to N-MORB, while those from the other sites are compositionally similar to E-type MORB or island arc basalts (IAB). The model ages T_Nd(DM) of eclogites vary between 1.95 and 0.67 Ga. The Sulu-Tyube eclogite yields the youngest age; it has the values of ε_Nd(T) (7.2) and ⁸⁷Sr/⁸⁶Sr (0.70393) close to the depleted mantle values. The crustal input to the protolith of the Kokchetav eclogites is evident on the ε_Nd(T)-⁸⁶Sr/⁸⁷Sr and ε_Nd(T)-T plots. The eclogites make up a trend from DM to country rocks. Some eclogites from the Kulet, Kumdy-Kol, and Barchy localities display signs of partial melting, such as high Sm/Nd (0.65-0.51) and low (La/Sm)_N (0.34-0.58) values. The equilibrium temperatures of these eclogites are higher than 850 °C. The geochemical features of eclogites testify to the possibility of the eclogite protolith formation in the tectonic setting of passive continental rift margin subducted to depths over 120 km.     

扬子地块西缘峨山新元古代A2型花岗闪长岩的成因及构造意义

在扬子地块西缘出露有大量的新元古代岩浆岩,这些岩石对于重建罗迪尼亚超大陆有着重要的意义。本文对云南峨山岩体的花岗闪长岩和似斑状黑云母二长花岗岩开展了详细的岩石学、岩石地球化学和年代学研究,结果表明,似斑状黑云母二长花岗岩侵位于826.6±2.5 Ma,而花岗闪长岩有着较年轻的结晶年龄818.3±2.8 Ma,花岗闪长岩比似斑状黑云母二长花岗岩有着更低的SiO₂含量,但是更高的Al₂O₃、MgO、Fe₂O₃、TiO₂和P₂O₅含量。在稀土元素配分曲线和微量元素蛛网图上,两种岩性呈现出相似的特征,都是具有右倾的稀土元素配分样式,呈现出Eu负异常,相对于大离子亲石元素（LILEs）更亏损高场强元素（HFSEs）。似斑状黑云母二长花岗岩富集Nd同位素组分,而花岗闪长岩与之有着相似的Nd同位素值。地球化学数据显示可能的岩石学成因是变质火成岩源区在826 Ma时发生部分熔融形成了峨山似斑状黑云母二长花岗岩并且残留下来了一个麻粒岩化的源区;麻粒岩源区在818 Ma时再次发生部分熔融形成了具有A型属性的峨山花岗闪长岩。结合前人的数据和本文的研究,认为扬子西缘在新元古代时期是一个活动大陆边缘,而华南地块当时在罗迪尼亚的位置更可能是在边缘而不是中心。     

冰核观测中两种滤膜采样方法的比较

大气冰核观测是研究自然冷云降水和人工影响天气的一项基础性工作,滤膜—扩散云室法是观测冰核浓度的主要方法之一。为检测分析两种滤膜采集方法对冰核观测结果的影响,2011—2015年用自制的大气颗粒物采样器和FA-3型撞击式9级采样器开展了平行采样试验,采集的滤膜样本均在同一静力扩散云室中进行冰核活化显现分析。结果表明：自制采样器较9级采样器观测的冰核浓度高数倍甚至数十倍,但两者随季节和不同气象条件的变化表现出一致的起伏特征。自制采样器适用于对大气中总的冰核浓度分布及理化特征研究;9级采样器适用于对PM₁₀中不同粒径段大气冰核浓度和尺度分布以及理化特征的研究。滤膜法对冰核数量的低估与采样体积成正比,改变采样器气泵的抽气流量和控制采样体积对改进“体积效应”影响均有明显效果。