滇西昌宁——孟连带西区两个地层问题——兼论昌宁——孟连带的闭合 …

对昌宁－－孟加带西区的两个地层问题进行了讨论。根据牙形刺和放射虫的发现将原定为拉巴组的塔拉弄－南雅条带的时代厘定为晚泥盆世至早石炭世,时代大致与南皮河群的弄巴组或“中区”的“上泥盆统”相当,它们之间的确切关系仍有待进一步研究。怕拍组实际上主体属晚二叠世晚期,仅顶部可能包含有少量下三叠统印度阶最底部的沉积。对怕拍组的研究证实了澜沧运动的存在,昌宁－孟连带自此开始了由海洋盆地向造山带的演变进程,这一过     

Early Paleozoic Structural and Metamorphic Evolution of Western Sierra de San Luis (Argentina), in Relation to Cuyania Accretion

Structural, metamorphic and isotopic data obtained from the Nogoli Metamorphic Complex of western Sierra de San Luis indicate that the Early Paleozoic Famatinian Orogeny overprinted an already structured and metamorphosed older basement. The older geological features are relict NW trending fabric associated with high-grade (amphibolite facies) regional metamorphism preserved within thin strips of schists and paragneisses and in the core of mafic to ultramafic lenses. Arc magmatism, medium P (Barrovian type)/high T (amphibolite to granulite facies) regional metamorphism and penetrative NNE to NE trending foliation are related to the building of the Famatinian orogenic belt. The P-T conditions of the Famatinian prograde metamorphism reached a pressure peak of ca. 8 kb, with a thermal peak from -750°C up to -820°C. U-Pb conventional and chemical dating and Ar-Ar plateau ages constrain the peak of the main orogenic phase related to the Famatinian belt to 470–457 Ma (Early to Mid-Ordovician). Greenschist facies retrograde metamorphism closely associated with shear zones and secondary Ar-Ar plateau and Sm-Nd ages suggest that a late to post-orogenic phase of the Famatinian belt was active at least since -445 Ma. This phase continued during the Silurian to Late Devonian times through multiple reactivation of early shear zones. The Famatinian Orogeny reset a previous thermal history and therefore, the timing of the relict fabric could not be constrained conclusively with radiometric dates. Despite this difficulty, a range of 520 to 490 Ma suggests some inheritance from Pampean events registered by the older NW-SE fabric. The Early to Mid-Ordovician regional metamorphism and ductile deformation of the western Sierra de San Luis is interpreted as the orogenic effects of the collision of the allochthonous Cuyania terrane with the autochthonous proto-Pacific margin of Gondwana during the Famatinian Orogeny.     

Diapiric emplacement in the upper crust of a granitic body: the La Bazana granite (SW Spain)

The ascent and emplacement of granites in the upper crust is a major geological phenomenon accomplished by a number of different processes. The active processes determine the final geometry of the bodies and, in some favourable cases, the inverse problem of deducing mechanisms can be undertaken by relying on the geometry of plutons. This is the case of the La Bazana granitic pluton, a small Variscan igneous body that intruded Cambrian rocks of the Ossa-Morena Zone (SW Iberian Massif) in the core of a large late upright antiform. The granite shows no appreciable solid-state deformation, but has a late magmatic foliation whose orientation, derived from field observations, defines a gentle dome. The regional attitude of the main foliation in the country rock (parallel to the axial plane of recumbent folds) is NW–SE, but just around the granite, it accommodates to the dome shape of the pluton. Flattening in the host rock on top of the granite is indicated by boudinaged and folded veins, and appears to be caused by an upward pushing of the magma during its emplacement. The dome-shaped foliation of the granite, geometrically and kinematically congruent with the flattening in the host rock, can be related in the same way to the upward pushing of the magma. The level of final emplacement was deduced from the mineral associations in the thermal aureole to be of 7–10 km in depth. Models of the gravity anomaly related to the granite body show that the granite has a teardrop–pipe shape enlarged at its top. Diapiric ascent of the magma through the lower middle crust is inferred until reaching a high viscous level, where final emplacement accompanied by lateral expansion and vertical flattening took place. This natural example suggests that diapirism may be a viable mechanism for migration and emplacement of magmas, at least up to 7–10 km in depth, and it provides natural evidence for theoretical discussion on the ability of magmatic diapirs to pierce the crust.     

库车坳陷沉降与天山中新生代构造活动

位于塔里木盆地北缘、天山南侧的库车坳陷为中新生代发育的构造单元。坳陷与天山造山带在成因上紧密相连，坳陷的沉降是由于天山山体隆升扩展引起的岩石圈挠曲响应。根据纵横向不同位置盆地沉降史的分析对比，该坳陷为典型的挤压盆地。推测中生代时期天山造山带以走滑和逆冲作用为主，新生代时期至少在库车坳陷北缘，天山造山带以向南冲断作用为主。库车坳陷强烈沉降时期并不对应于粗碎屑沉积，而对应于细碎屑沉积时期，即天山造山带构造强烈活动时期。天山造山带强烈活动造成库车坳陷强烈沉降，其主要原因与塔里木板块南侧的羌塘地体、拉萨地体、科西斯坦杂岩和印度次大陆的增生碰撞有关。     

下扬子独立地块与中生代改造型残留盆地

下扬子地块在古纬度、火山岩和花岗岩时空发育、区域成矿专属性、沉积建造和构造变形等方面具独特性,与扬子地块有显著差异,是一个晚古生代——中生代早期的独立地块。受燕山期苏鲁板间造山作用影响,下扬子地块直至燕山中期才“楔入”在印支期已拼合的扬子与华北地块,从而演化成独特的下扬子改造型残留叠合盆地。这种改造型叠合盆地的基本特点是:晚印支-早燕山同造山期前陆盆地沉积层和上叠的中燕山期陆相沉积层遭受大量剥蚀,并与古生-中生界海相沉积层一起被卷入强烈的多期次的燕山造山运动,晚白垩世——古近纪又强烈反转成为断陷盆地,形成鲜明的上部地壳的双层结构。这是造成下扬子地区海相古生-中生界油气地质勘探高复杂性、高难度性和高风险性的根本原因,也造就了下扬子区海相烃源岩的二次生烃和晚期成藏的优势。     

Financial statement as at 31 December 1969

The Tasman Line, a much‐discussed concept in the geology and tectonics of eastern Australia, has a long and chequered history of interpretation. This extends to current debates regarding the age and position of the Tasman Line in Gondwana‐Rodinia reconstructions. We present constraints, from mapping, geochemistry and geophysics, on the interpretation of gravity and magnetic lineaments attributed to the Tasman Line in New South Wales, South Australia, Victoria and Tasmania. These pieces of evidence suggest a protracted and complex latest Neoproterozoic to Carboniferous geological history that produces a variety of geophysical responses, rather than a simple ‘Line’. We also find no evidence of Rodinian breakup age activity responsible for any of the anomalies. In light of these findings, our preference is that the Tasman Line concept be abandoned as misleading, especially with regard to models of Rodinia‐Gondwana breakup, which must have occurred elsewhere, possibly well to the east. Instead, the rocks preserved in the westernmost part of the Tasmanides are consistent with previously proposed ‘Southwest Pacific’‐style models for Neoproterozoic continental breakup, margin formation and reaccretion of continental fragments in the Early Palaeozoic.     

A Pan-African alkaline pluton intruding the Saramuj Conglomerate,south-west Jordan

The geological setting, petrography and bulk mineral chemistry of a monzodiorite and a presumably consanguineous megaporphyry with large (up to 25 cm) labradorite megacrysts, both intruding the upper Proterozoic Saramuj Conglomerate in south-west Jordan (south eastern shore of the Dead Sea), were examined. The crystallization temperatures of the monzodiorite and the megaporphyry as determined from pyroxene thermometry and supported by contact metamorphic mineralogy are about 700 and 900°C, respectively. The intrusion depth of the monzodiorite is about 3–4 km. The monzodiorite was emplaced in the Saramuj Conglomerate at about 595 + 2 Ma ago according to Rb/Sr and U/Pb age determinations.The stratigraphic positions of the monzodiorite, megaporphyry and their host rock (the Saramuj Conglomerate) were compared with time-equivalent lithologies in the Arabian-Nubian Shield. Correspondence to: H. Wachendorf     

庐山运动

本文简述了庐山隆-滑构造的基本特征。在中元古代双桥山群底部的顺层韧变带中，把前人的断层构造砾或沉积成因的巨厚层状变质复成分砾岩，自上而下分离出三层砾：上部砾、中部砾、下部砾。其中上部砾为断层构造砾；中部砾不是砾，而是构造分泌物；下部砾为沉积底砾。在此基础上，同时参考研究区早元古代星子群与中元古代双桥山群构造、岩浆活动、变质作用等方面的差异，建立了“庐山运动”，其活动时间为2200～1800Ma，这可以与华北及华南其它地区同时期的构造运动相对比，但庐山运动的强度相对较弱，表现为以垂直隆升为特色的造陆运动，它曾使研究区早元古代晚期至少遭受过长达200Ma（1800～1600Ma）的风化、剥蚀作用。     

泰国Khorat盆地二叠纪石灰岩的重磁化研究

泰国Ｋｈｏｒａｔ盆地西部的晚二叠世石灰岩的古地磁研究表明磁铁矿为稳定剩磁的主要载体多组分磁分量分离技术揭示了高温磁组分（或高矫顽力）具有呈对分布的正、反极性．但是，应用逐渐展平岩层法可以发现各采样点的平均特征磁化方向在岩层展平至３０％时．磁化方向最为集中．这一发现表明二叠纪石灰岩中所揭示出的磁化方向很可能形成于褶皱（期）过程中．野外观察表明，二叠纪石灰岩在印支期发生强烈褶皱并被晚三叠世湖相石灰岩角度不整合覆盖．所以二叠纪石灰岩的重磁化很可能发生在中、晚三叠世的印支期．这些石灰岩样品切片后经显微镜、扫描电镜和电子探针分析，次生磁铁矿多数与方解石微晶和铁质碳酸钙粒共生，且多分布在方解石脉附近．重磁化很可能是由于印支期造山运动时，铁质碳酸钙受碳水化合物流体的蚀变作用所引起的。