泰国北部三叠系Lampang群Doi Long组的有孔虫组合与沉积环境

A rich foraminiferal assemblage, consisting of abundant Aulotortus sinuosus and A. tumidus in association with Lamelliconus multispirus, Endoteba ex gr. controversa, E. ex gr. badouxi, Endotebanella kocaeliensis, Endotriada tyrrhenica, Endotriadella wirzi, Malayspirina fontainei, Ammobaculites rhaeticus, Diplotremina astrofimbriata, Agathammina austroalpina, and others, was found in the Doi Long Formation of the Triassic Lampang Group, Northern Thailand. These foraminifers suggest that the formation is referable to the Carnian (early Late Triassic), which is consistent with the age estimated by ammonoids. In microfacies, peloidal grainstone, bioclastic grainstone, sponge-microbial boundstone, and oolitic grainstone were recognized in the Doi Long Formation. Based on microfacies, three depositional facies, the lagoon facies, reef facies, and shoal facies, are recognized in this formation. These lines of evidence are suggestive that the Doi Long Formation was deposited in a reef or bank setting rather than a ramp setting.     

Huanggang Intrusive Complex in Northern Tongbai Area: Island-Arc Tectonic Environment and Its Geological Significance

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西秦岭断裂构造系统基本特征及其对地质灾害的控制 作用

通过对青藏高原东北缘西秦岭地区断裂构造系统的特征及与滑坡、泥石流等地质灾害关系的分析研究,探讨了断裂构造系统对滑坡、泥石流等地质灾害的形成和分布的控制作用。认为虽然滑坡、泥石流等地质灾害是内外动力地质作用复杂的联合作用的结果,但断裂构造系统及其活动性对滑坡、泥石流等地质灾害形成具有关键性的作用,这种作用方式有直接和间接之分。西秦岭地区典型的滑坡、泥石流等的形成大多与断裂构造及其活动密切相关,主要表现在:(1)断裂构造发育的区域一般是滑坡、泥石流高发区;(2)断裂带活动为滑坡和泥石流的发生提供了物源和结构条件;(3)断裂的地震活动是诱发滑坡的关键因素;(4)断裂带的长期活动形成的构造破碎带和地形高差易于为流水的侵蚀而形成泥石流沟和陡坡地形。因此在对滑坡、泥石流等地质灾害研究中,不应孤立的认识单个滑坡、泥石流的形成与发展,而应把其放在区域地质环境演化中去认识,尤其是把区域断层格架、断层带结构和断层活动性研究作为地质灾害形成与发展的关键影响因素深入研究,从而为科学认识崩塌、滑坡、泥石流等地质灾害的形成过程、制定科学的灾害的防御和治理方案提供科学依据。     

安徽大别山北部红刚玉岩石的成因

大别山北部红刚玉矿产在太古代大别山群黑云角门外长片麻岩以及超基性岩中。赋存红刚玉的刚玉黑云二长片麻岩的原始岩石为富铝泥质岩,在角门岩相变质条件下,通过两种脱硅方式,即变质分异作用和超基性岩侵位,形成刚玉黑云二长片麻岩。它们形成的温压条件：Ｔ＝５００℃～７００℃,Ｐ＝０．４～０．７ＧＰａ。刚玉形成的可能的化学机制是白云母在缺硅条件下的分解。     

中生代复杂构造体系的成矿过程与成矿作用——以华北大陆北缘西拉木伦钼铜多金属成矿带为例

西拉木伦钼铜多金属成矿带处于华北克拉通与中亚造山带的过渡区,是古生代古亚洲构造域与中生代西太平洋构造域的交汇部位。在中生代受多种构造体系的制约,如中亚造山带造山后期局部伸展、蒙古-鄂霍茨克俯冲-碰撞造山作用、古太平洋板块的向西俯冲和中国东部岩石圈减薄事件的影响等。西拉木伦成矿带成矿斑岩锆石U-Pb年龄和辉钼矿Re-Os同位素年龄资料显示,钼铜矿成岩成矿主要集中在260～220Ma、180～150Ma和140～120Ma三个时期。结合华北克拉通北缘构造演化历史,推测这三期成矿作用主要与造山后局部伸展、构造体系转折和陆内伸展(岩石圈减薄)过程有关,并相应建立了"车户沟式"、"鸡冠山式"和"敖伦花式"三类斑岩钼铜矿床成矿模式。进一步研究表明,岩石的酸碱性、岩浆来源、岩浆的氧逸度、岩浆演化方式、构造背景等因素,制约了成矿作用的专属性。     

1605年海南岛琼州大地震及其发震构造的初步探讨

琼北地区铺前−清澜断裂是一条关系到1605年琼山7½级大地震发震构造判断的重要断裂。为准确厘定该断裂的最新活动特征,针对琼北地区第四纪玄武岩盖层和巨厚海相砂沉积等地质条件,采用大吨位震源的浅层人工地震勘探和小间距钻孔联合地质剖面探测相结合的方法,分别在海口江东三江镇岐山头村和东寨村展开探测。结果表明：(1) 铺前−清澜断裂断错了多个标志地层,最浅断错至全新统烟墩组淤泥层,上断点埋深10 m左右,钻探所揭示的断层面明显具有走滑兼具逆冲性质,是一条具有一定宽度、多分支、多期次活动的大规模断裂带;(2)钻孔联合地质剖面所揭示的地层深度范围内,被断错地层的位移量随着深度增加而加大,铺前−清澜断裂自8 346~7 153 a cal BP以来有过活动,全新世累计垂直位移量4~5 m,垂直位移速率为0.53~0.63 mm/a,推断其为1605年琼山大地震的发震断裂。本研究取得的铺前−清澜断裂全新世活动的新证据,为国土空间规划和区域地震危险性评价提供了科学依据。

     

北秦岭四方台基性-超基性杂岩锆石 LA-ICP-MS年代学研究

四方台杂岩体是北秦岭沿商-丹带出露的基性-超基性杂岩体中最大的一个,出露面积约40 km2,由超基性-基性-中性岩石组成,侵入到丹凤群中。对四方台杂岩体中辉长岩锆石进行LA-ICP-MS微区定年研究,获得岩体的成岩时代为460±29 Ma。获得的32个测点可明显地分为400~500 Ma、700~900 Ma、1 800~2 600 Ma和2 700~2 918 Ma这4个时段,可能分别代表了北秦岭造山带不同地质时期的构造-岩浆事件的时代信息。其中400~500Ma与北秦岭地区表现强烈的加里东运动时限一致,而700~900 Ma则可能与830~740 Ma中国中西部地区响应积极的、造成Rodinia超大陆裂解的地幔柱活动有关。     

History of faulting in the Northern Hastings Block,southern New England Orogen

Brittle failure is common in the Devonian to Permian rocks in the Northern Hastings Block (NHB) and is manifested by faults of different orientation and kinematic histories, but the timing of fault movement is not well defined. In this study, faults in the NHB were analysed with the map pattern of cross-cutting faults used to estimate the relative time of movement and relationship to other faults. We defined five episodes of faulting or fault reactivation that affected the NHB. The Yarras Fault System on the southwestern side of the NHB and the Parrabel Fault and related faults on the eastern side of the NHB are the two major fault systems responsible for transporting and rotating the NHB in the late Carboniferous. Faults on the eastern, northeastern and northern part of Parrabel Dome started and stopped moving after emplacement of the Hastings Block and before the intrusion of the Werrikimbe Triassic granitoids. We suggested that the movement on the major bounding faults is related to the accommodation of the NHB to the folding and cleavage development in the adjoining Nambucca Block, and is associated with the earliest part of the Hunter–Bowen Orogeny. Limited dextral movement on the extensions of the Taylors Arm Fault System caused minor displacements in the northeastern part of the NHB during the Late Triassic. Some small faults cut the Triassic granitoids or Triassic Lorne Basin sediments indicating tectonic activity continued post-Triassic.     

Mapping Proterozoic unconformity-related uranium deposits in the Rockhole area, Northern Territory, Australia using landsat ETM+

The Rockhole area, Northern Territory, Australia, hosts a number of Proterozoic unconformity-related uranium deposits. The geology of the area features within Paleoproterozoic rocks of the Pine Creek Orogen, near the unconformity with overlying platform cover sandstone of the Paleo- to Mesoproterozoic McArthur Basin. Landsat Enhanced Thematic Mapper plus (ETM+) data was used in the Rockhole area to assist in mapping geological structures and lithology, and to identify anomalous concentrations of ferrous minerals, the product of alteration, which can be indicators of buried uranium mineralization. Several image-processing procedures were applied to the ETM+ data to identify, isolate and enhance mineralogical information as simple and complex false color composites. ETM+ 754 shown as red green and blue respectively was the best simple image. Overall, complex images based on Principal Component Analysis proved to be the most useful products. Sandstone, shale and siltstone, the target lithologies, Koolpin Formation, the target stratigraphic unit, and bleaching pattern due to the removal of iron(II) compounds, the target alteration pattern, were confidently mapped to provide information required by the mineral emplacement model, which ultimately identified areas of likely uranium mineralization. Thus the contrasting behavior of the two principle oxidation states of uranium and iron can be utilized to map/delineate bleached alteration zones associated with economic concentrations of uranium using multispectral sensors like Landsat or better hyperspectral sensors.