Tmax of asphaltenes: a parameter for oil maturity assessment

A new maturity parameter determined on both oil and bitumen samples, the asphaltene T_max, is proposed and discussed. This parameter could be very useful to address the maturity of the source rock. The asphaltene T_max is measured by programmed Rock-Eval pyrolysis, using a modified temperature program. Some phases of the experimental procedure, such as the asphaltene preparation and the Rock-Eval measurement substratum choice, are crucial in order to achieve reliable data. Laboratory simulations were carried out in order to assess the possible effects of both primary and secondary migration on asphaltene T_maxin the expelled oil: the original value of the asphaltene T_max in the bitumen is not substantially modified and it is very close to that measured on kerogen. Examples of the determination of asphaltene T_max on many samples, collected from different areas and with different organic matter composition, are given. Results show that T_max values from oil asphaltenes are reasonable indicators of source rock maturity.     

DISCUSSION ABOUT THE PETROGENESIS OF THE CENOZOIC VOLCANIC ROCKS FROM YUMEN AND HOH XIL AREA, QINGHAI-TIBET PLATEAU

DISCUSSION ABOUT THE PETROGENESIS OF THE CENOZOIC VOLCANIC ROCKS FROM YUMEN AND HOH XIL AREA, QINGHAI-TIBET PLATEAU     

大兴安岭—燕山晚中生代岩浆活动与俯冲作用关系

本文通过对华北的大兴安岭－燕山地区晚中生代火山－深成岩岩石化学、同位素地质学的分析，认为该地区岩浆的形成和演化与板内伸展环境下的底侵作用有关，而与太平洋板块俯冲无直接的成因联系。本文展示了较高分辨率的日本海沟－长白山－蒙古额尔德尼查干的地震层析图像，揭示了太平洋俯冲板片的形态特征；再结合对俯冲时间及俯冲作用与岩浆作用时差的研究，进一步证明板块俯冲与研究区的岩浆活动无直接关系。最后通过底侵作用年代学的研究，将大兴安岭－燕山中生代岩浆活动与层析图象显示的大陆板内软流圈上涌体联系起来。     

Implications of εNd—La／Nb,Ba／Nb,Nb／Th Diagrams to Mantle Heterogeneity—Classification of Island—arc Basalts and Decomposition of EMII Component

A group of εNd/Nb,Ba/Nb,Nb/Th diagrams are used to study mantle heterogeneity.Island-arc basalts(IAB) are distributed in a triangle of these diagrams. Three end-member components (the MORB-type depleted mantle, the fluid released from subducted oceanic crust and the sediments from the continental crust) of the source of IAB may be displayed in these diagrams. Two types of IAB are identified .They are of the two-component type (with little continental sediments), such as the basalts from Aletians and New Britain ,and the three-compeonent type, such as those from Sunda, Lesser Antilles and Andes. In addition ,the EMII type mantle-derived rocks may also be divided into two groups. One is exemplified by continental flood basalts and some peridotite xenoliths, similar to IAB, with high La/Nb and Ba/Nb and low Nb/Th ratios, The other includes the Samoa-type oceanic island basalts, with low La/Nb and Ba/Nb and high Nb/Th ratios. The corresponding two sub-components of EMII are EMIIM, which is related to the metasomatism of lithosphere mantle by fluids released from the subducted oceanic crust, and EMIISR, related to the intervention of recycling continental sediments into the convective mantle.     

磁法勘探在新疆尉犁县且干布拉克蛭石、磷灰石矿床普查评价中的应用效果

尉犁县且干布拉克蛭石矿为特大型,磷灰石矿为大型.蛭石、磷灰石均赋存于磁性较强的透辉石岩及超基性岩中,矿体与围岩间有较明显的磁性差异,含矿母岩70%被第四系覆盖.利用地面磁测,较好地圈定了含矿母岩的边界,提供了含矿体的平面形态及产状,为勘查缩小了靶区.磁法勘探不仅是直接找磁铁矿床及某些有关金属矿床的有效方法,而且在间接寻找非金属矿床上亦能发挥作用.     

Tektonisches Verhalten und geologische Bedeutung von Kalksilikatfels-Lagen und -Spindeln im Damara-Orogen Südwest-Afrikas

Zusammenfassung Beschrieben wird das Verhalten von frühdiagenetisch gebildeten schichtparallelen Kalksilikatfels-Lagen, -Linsen, -Knollen und diffusen Ansammlungen während der Gesteinsdeformation in Teilen des Damara-Orogens. In Abhängigkeit von ihrer relativen Löslichkeit und/oder Kompetenz sowie vom Winkel zwischen Schichtung und Schieferung können Lagen und Linsen als solche erhalten bleiben oder in spindelförmige Körper zerlegt werden (Verkürzungsboudinage). Knollen werden zu Ellipsoiden oder Spindeln deformiert und diffuse Kalksilikatfels-Ansammlungen in eine Vielzahl von Spindeln aufgelöst. Alle im Zusammenhang mit der Anlage der Schieferung gebildeten Spindeln und Ellipsoïde sind streng in der Schieferung orientiert. Es wird deutlich, daß die Spindelform der Kalksilikatfels-Körper ein Produkt der Gesteinsdeformation ist.In Gebieten, in denen der Verdacht besteht, daß parallel zu einem deutlichen Materialwechsel eine Schieferung verläuft, kann aus der Existenz von Spindeln auf das Vorhandensein dieser Schieferung geschlossen werden.Die ungleichmäßige Verteilung von Kalksilikatfels-Körpern innerhalb der Khomas-Serie ermöglicht eine Unterteilung dieser bisher ungegliederten, bis zu 6000 m mächtigen Gesteinsfolge.

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The behaviour during rock deformation of diagenetically formed layers, lenses, nodules (concretions) and diffuse concentrations of calc-silicate rock is described from parts of the Damara belt. Depending on their relative solubility and/or competency and on the angle between bedding and cleavage planes the layers and lenses may either more or less retain their shape or be cut up into spindle-shaped bodies (boudinage due to shortening). Nodules are deformed to ellipsoides, while diffuse concentrations of calc-silicate rock are transformed into a number of spindles. All spindles and ellipsoides which are formed during the formation of the cleavage are strictly orientated parallel to the cleavage planes. It is therefore obvious that the spindleshape of these bodies is a consequence of rock deformation. Thus, in areas in which a cleavage is suspected to lie parallel to a distinct bedding, the occurrence of spindles may confirm the existence of this cleavage.The non-statistical occurrence of calc-silicate rock bodies within the Khomas Series may render possible a first subdivision of this up to 6000 m thick succession.

Diese Arbeit ist im Sonderforschungsbereich 48 Entwicklung, Bestand und Eigenschaften der Erdkruste, insbesondere der Geosynklinalräume, Göttingen, entstanden.     

Some foundation stability problems of the railway bridge over the Mala Rijeka

SummarySome Foundation Stability Problems of the Railway Bridge over the Mala Rijeka The authors presented an outlay of problems occurring in estimating the stability of rocky slopes loaded by large vertical forces. General attitudes, kept by the authors during the stability analysis for an actual case — foundation of piers No. 3 and 4 of the railway bridge across the Mala Rijeka, are also presented. The results of calculation as well as the advantages of the approach applied are outlined in the paper. Finally, general conclusions are drawn regarding the method to be kept in solving the stability of slopes loaded by large artificial loading.With 7 Figures     

对变质岩区加强岩石学研究的几点看法

文章对1:5万区调工作中变质岩区加强基础岩石学工作的以下3个方面提出了一些看法,1．岩石薄片的研究;2．矿物化学和地质温压计;3．变质岩的岩石组合和构造环境。     

灰岩成因-结构分类的进展及其相关问题讨论

由Folk在1959，1962年及Dunham在1962年所提出的灰岩因－结构分类体系，具有划时代的意义，至今还得到极为广泛的应用，Embry和Klovan在1971年关于生物礁灰岩的成因－结构分类，即关于骨架灰岩，障积灰岩，粘结灰岩的成因－结构分类的第一次重要的补充，它解决了与生物作用有关的灰岩不符合Folk和Dunham的结构成熟度概念的矛盾，而对成岩作用及其产物的更深入研究，地质学家们发现了许多布成岩作用形成的泥晶化作用和颗粒化作用，由它们所形成的岩石也不符合Folk和Dunbam的结构成熟度概念，导致了Wright在1992年提出了一个更完整的灰岩成因－结构分类体系，把灰岩分为生物作用类，沉积作用类及成岩作用类三大类，即Folk和Dumban描述的分类均属于沉积作用类。要特别指出的是，在从松散沉积物到已石化的竖硬石头的成岩过程中，不但灰岩的结构会发生变化，而且组分也会发生变化，从而使灰岩的成因－结构分类变得更加复杂，关于这方面还存在许多有待进一步研究的问题。在审视Wright在1992年的分类体系时，有必要在沉积作用类中增加“非正常沉积作用亚类灰岩”，针对许多非礁相地层中发育的由生物礁岩石构成的生物层及生物丘，因而有必要对生物作用灰灰岩进行更进一步的分类。     

澜沧江某电站右坝肩复杂岩体质量分类

笔者通过对澜沧江某电站右岸坝肩复杂岩体的成因进行分析,采用岩体质量指数Z并结合水利水电工程围岩分级和RMR分级等岩体分类方法对电站右岸坝肩的复杂岩体进行了综合分类。