Sunrise Hill unconformity: A newly discovered regional hiatus between Archaean granites and greenstones in the northeastern Pilbara Craton

Contacts between Archaean granites and greenstones in the northeastern part of the Pilbara Craton have been described as intrusive and tectonic. New field observations in the Shay Gap region demonstrate that greenstones of the Gorge Creek Group unconformably overlie the Muccan and Warrawagine batholiths. Regionally, the unconformity is marked by a persistent but relatively thin basal clastic sequence, locally with a granite boulder conglomerate, overlain by ore‐bearing banded iron‐formation, fine‐grained clastic rocks and chert. The granite basement is dated at 3443 ± 6 Ma. The precise age of the hiatus is unknown but its maximum effect might have been the removal of a substantial thickness of Early to Middle Archaean strata.     

The Eltanin asteroid impact: possible South Pacific palaeomegatsunami footprint and potential implications for the Pliocene–Pleistocene transition

Large asteroid impacts are rare, and those into the deep ocean are rarer still. The Eltanin asteroid impact around 2.51 ± 0.07 Ma occurred at a time of great climatic and geological change associated with the Pliocene–Pleistocene boundary. Numerical models of the event indicate that a megatsunami was generated, although there is debate concerning its magnitude and the region‐wide extent of its influence. We summarise the existing evidence for possible Eltanin megatsunami deposits in Antarctica, Chile and New Zealand, while also examining other potential sites from several locations, mainly around the South Pacific region. In reviewing these data we note that these events were unfolding at the same time as those associated with the Pliocene–Pleistocene boundary and, as such, most of the geological evidence from that time has a climatic interpretation. The potential climatic and geological ramifications of the Eltanin asteroid impact, however, have failed to be considered by most researchers studying this time period. Although we are not advocating that all geological activity at that time is connected with the Eltanin asteroid impact, it raises interesting questions about the role potentially played by such catastrophic events in contributing to or even triggering epochal transitions. Copyright © 2012 John Wiley & Sons, Ltd.     

应用地层放射性元素地球化学参数评价地层含铀远景

根据放射性元素地球化学特性和岩相建造理论,作者研究了沉积建造层位中U、Th、K的分布特征,以及它们的组分参数MA、MB同地层铀富集矿化程度的关系,通过不同矿化程度的地层中MA和MB的对比,得出4种类型矿化程度的含铀层位的MA和MB值范围,为采用放射性元素的多参数定量评价地层含铀远景提供了一定经验。     

江西弋阳港口盆地林山组地层时代讨论

本文讨论了江西弋阳港口盆地林山组中的植物化石群。根据其组份特征,可确定该地林山组时代为早侏罗世中晚期,可与鄂西香溪组中下部的植物群对比。     

川西高原砂金矿床形成规律

砂金富集规律可归纳为五条:(1)砂金比重大,体积小,一般下沉于砂砾层底部基岩之上,形成富矿带。(2)河流流速减缓处是砂金富集之场所,如河流内湾处;两河会流处;河谷由宽突变窄处;河谷由窄突变宽处。(3)河床起伏不平是砂金富集之主要条件。最理想的河床是软硬相间之岩层,如砂页岩互层,且走向横穿河谷,倾斜较陡,这样,便形成具有无数隔梁与隔槽的起伏不平的河床,砂金受阻,易于停积。(4)位于谷旁之古老河床沉积阶地是无水患的易采砂金矿床,不容忽视。(5)红黄杂色铁砂及石英碎屑常为砂金富集标志。     

新疆巴里坤晚志留世地层及四射珊瑚

新疆巴里坤地区晚志留世地层比较发育,层序清楚,化石丰富,其中珊瑚和腕足类最多.巴里坤地区上志留统叫阔克赛尔克组,又分上下两亚组.下亚组丰产床板珊瑚和四射珊瑚.如Holmophyllum,Kodonophyllum,Tryplasma,Chlamydophyllum,Rhizophyllum,Kyphophyllyum,Entelophyllia,Cymatelasma,Cyathophylloides,Micula.Pilophyllum,Pseudamplexus,Ramulophyllum,SPongophyllum,Spongophyl-loides,Nanshanophhpllum and Thecia,Mesofavosites,Favosites,Pentamerus等,厚76—221m.上亚组仅含一些蜂巢珊瑚(Favosites),厚158—170m.阔克赛尔克山上志留统阔克赛尔克组的生物群落是很特殊的,可与吉林省二道沟区小绥河组.辽宁省昭乌达盟敖汉地区的下石碑组及内蒙自治区百灵庙北的巴特敖包群对比,显然,阔克赛尔克组的地质时代相当晚志留世罗德洛阶.     

陕西金堆城钼矿床中铁钼华的矿物学特征及其意义

铁钼华产于陕西金堆城斑岩钼矿床的氧化带内,该矿物以往被认为是钼华。笔者对该矿物进行了物理光学性质、化学成分、X射线衍射、穆斯堡尔谱、红外光谱以及失重和差热分析的研究,定名为铁钼华,其分子式为Fe_2(MoO_4)_3·6.8H_2O。同时,将其与国外天然和人工合成的铁钼华作了对比,确定其是在酸性氧化环境中形成的次生矿物。它是原生钼矿床的直接找矿标志。     

赣西南下奥陶统樟木曲组笔石带的修正和补充

本文在对笔石作系统研究的基础上,对樟木曲组的笔石带进行了补充和修正。由原来的9个笔石带划分为11个笔石带,厘定了各笔石带的范围和笔石群的总体面貌,并逐带与国内外进行了对比。文内还涉及到宁国阶的顶界、上下两层下垂时笔石以及关于肿笔石与心笔石混生的问题。     

Two bioerosion ichnofacies produced by early and late burial associated with sea-level change

In bioerosion, as in trace fossils as a whole, deeply emplaced structures have greater survival value than shallow structures. That is to say, tiering (the relative depth to which rasping, etching and boring organisms penetrate their substrate) is of paramount importance for the preservation potential of individual trace fossils. An Entobia ichnofacies is established for trace fossil assemblages dominated by deep tier borings and arising from long-term bioerosion, such as occurs on sediment-free submarine cliffs or hardgrounds. A Gnathichnus ichnofacies comprises assemblages containing all tiers, including superficial sculptures produced by radulation that have very little preservation potential. Such assemblages occur in short-term bioerosion situations as on shell surfaces and hardgrounds buried early by sedimentation. Correspondence to: R. G. Bromley     

滇中郝家河砂岩铜矿的地球化学及其成因意义

本文论术字滇中生代地层与矿区及春外围马头山组中铜的时空分布与迁移富集规律，揭示了矿床的沉积－后期叠加改造成因。成矿作用经历了同生沉积形成矿源层，后期叠加改造形成矿体的过程。后期改造中铜元素发生了大量迁移，矿质主要来自矿体之下伏紫色矿源层。