Geologic and geotechnical effects of an impact caused by an airplane crash

A Turkish Airlines (THY) Boeing 737-400 plane crashed into alluvial soils creating an approximately 13 m deep and 30 m wide crater near the village of Adatepe, Ceyhan in southern Turkey. Effects of the impact on the soils in and around the crater were investigated from both the geological and soil mechanics point of view.

The results show that the impact caused severe deformations in the soils in and around the crater. The soils deformed similar to metamorphic rocks seen at many terrestrial hypervelocity impact craters around the world and became overconsolidated up to a distance of about 10 m from the crater wall as a result of the impact.

Also, the crash was recorded as a 2.7 magnitude earthquake by a nearby microtremor seismograph which provided both the location (epicenter) and time of the crash which was not known immediately after the crash.     

Orogenic Gold Mineralization in the Qolqoleh Deposit, Northwestern Iran

The Qolqoleh gold deposit is located in the northwestern part of the Sanandai‐Sirjan Zone, northwest of Iran. Gold mineralization in the Qolqoleh deposit is almost entirely confined to a series of steeply dipping ductile–brittle shear zones generated during Late Cretaceous–Tertiary continental collision between the Afro‐Arabian and the Iranian microcontinent. The host rocks are Mesozoic volcano‐sedimentary sequences consisting of felsic to mafic metavolcanics, which are metamorphosed to greenschist facies, sericite and chlorite schists. The gold orebodies were found within strong ductile deformation to late brittle deformation. Ore‐controlling structure is NE–SW‐trending oblique thrust with vergence toward south ductile–brittle shear zone. The highly strained host rocks show a combination of mylonitic and cataclastic microstructures, including crystal–plastic deformation and grain size reduction by recrystalization of quartz and mica. The gold orebodies are composed of Au‐bearing highly deformed and altered mylonitic host rocks and cross‐cutting Au‐ and sulfide‐bearing quartz veins. Approximately half of the mineralization is in the form of dissemination in the mylonite and the remainder was clearly emplaced as a result of brittle deformation in quartz–sulfide microfractures, microveins and veins. Only low volumes of gold concentration was introduced during ductile deformation, whereas, during the evident brittle deformation phase, competence contrasts allowed fracturing to focus on the quartz–sericite domain boundaries of the mylonitic foliation, thus permitting the introduction of auriferous fluid to create disseminated and cross‐cutting Au‐quartz veins. According to mineral assemblages and alteration intensity, hydrothermal alteration could be divided into three zones: silicification and sulfidation zone (major ore body); sericite and carbonate alteration zone; and sericite–chlorite alteration zone that may be taken to imply wall‐rock interaction with near neutral fluids (pH 5–6). Silicified and sulfide alteration zone is observed in the inner parts of alteration zones. High gold grades belong to silicified highly deformed mylonitic and ultramylonitic domains and silicified sulfide‐bearing microveins. Based on paragenetic relationships, three main stages of mineralization are recognized in the Qolqoleh gold deposit. Stage I encompasses deposition of large volumes of milky quartz and pyrite. Stage II includes gray and buck quartz, pyrite and minor calcite, sphalerite, subordinate chalcopyrite and gold ores. Stage III consists of comb quartz and calcite, magnetite, sphalerite, chalcopyrite, arsenopyrite, pyrrhotite and gold ores. Studies on regional geology, ore geology and ore‐forming stages have proved that the Qolqoleh deposit was formed in the compression–extension stage during the Late Cretaceous–Tertiary continental collision in a ductile–brittle shear zone, and is characterized by orogenic gold deposits.     

湘西合仁坪钠长石-石英脉型金矿床围岩蚀变及质量平衡

湘西柳林汊一带钠长石-石英脉型金矿十分发育。为了揭示该区金矿的成矿物质来源、成矿过程及成矿流体信息,对该区最典型的合仁坪钠长石-石英脉型金矿床围岩蚀变特征进行研究,并利用标准化Isocon图解法,对围岩蚀变过程中物质带入、带出进行质量平衡计算。结果表明:合仁坪金矿床的围岩蚀变主要包括绢云母化(褪色化)、黄铁矿化和绿泥石化,其中褪色化分布最为广泛,是该区金矿床最重要的蚀变类型;在合仁坪金矿床形成过程中,围岩中的Al2O3为惰性组分,Na2O、Sr、V、Cr、W、Nb、Th及部分挥发分(S、CO2和H2O)等组分被带入围岩中,而SiO2、Fe2O3、K2O、CaO、MgO、Cu、As、Pb、Zn、Ni、Co、Sb、Li、Rb、Ba等组分从围岩中迁出;轻稀土元素的迁出程度远远大于重稀土元素,围岩蚀变过程中轻、重稀土元素发生强烈的分异;矿脉中钠长石的钠质并非来自赋矿围岩,而是由成矿流体从外界带入的;矿脉石英中硅质则部分来自赋矿围岩。     

卢氏西虎岭黄铁矿床围岩蚀变特征及其找矿意义

文章通过对西虎岭黄铁矿床围岩蚀变的研究认为，围岩蚀变大致可分为６种基本蚀变类型，５个蚀变阶段，３个蚀变带。各蚀变带以矿体为中心对称分布，各带之间呈渐变过渡关系。同时认为矿床成因类型属中低温热液充填型，并指出围岩蚀变的找矿意义。     

洛宁铁炉坪银铅矿床围岩蚀变分带特征

本文通过对铁炉坪银、铅矿床围岩蚀变的研究，划分出６种基本蚀变类型，３种蚀变带。各蚀变带以矿体为中心对称分布，各带之间呈渐变过渡关系。并指出由蚀变作用引起围岩化学成分及微量元素含量的变化，岩石化学成分与矿物成分变化相一致，成矿与围岩蚀变相辅相成。还指出了围岩蚀变的找矿意义。     

中国微细浸染型金矿床围岩蚀变地质特征

微细浸染型金矿的围岩蚀变一般较弱,主要蚀变类型以硅化、碳酸盐化、粘土化、绢云母化为主;围岩蚀变与容矿岩石类型及其岩性组合密切相关,化学组分的变化因围岩的性质而异;金矿化强度与围岩蚀变强度和蚀变组合复杂程度成正比,金矿体出现在蚀变中心部位或蚀变分带的内带.     

模糊层次综合评价在深埋隧道围岩质量分级中的应用

针对现行隧道围岩分类中存在的"模糊性"问题,引进模糊层次分析模型,实现了围岩定性分类向定量分类的转变,经过工程实践取得了良好的效果.首先确定了影响隧道围岩质量的主要因素,如岩块坚硬程度、结构面发育程度、岩石质量指标以及地下水出水特征,然后建立了模糊评价模型,并采用层次分析法确定了各因素的权重,最后针对堡镇铁路隧道围岩采用模糊层次综合评价决策的数学模型所得到的结果对隧道各段岩体质量的级别进行了划分.     

金家庄超基性岩型金矿围岩蚀变地球化学研究

金家庄金矿近围岩蚀变为蛇纹石化、滑石化、碳酸盐化和硅化。岩石化学与微量元素研究表明,从未蚀变－强蚀变透辉岩至矿化蚀变岩,ＳｉＯ２、ＣａＯ、Ａｌ２Ｏ３含量逐渐降低,ＣＯ２、Ｈ２Ｏ、Ｓ和Ａｕ、Ａｇ、Ｃｕ含量逐渐增高。蚀变岩石同位素研究揭示,碳同位素较低（δ＾１８Ｏ＝１２．１０‰～２２．３‰）远高于超基性岩正常范围。围岩蚀变热液主要源于大气降水、碳、硫和成矿元素主要是在围岩蚀变过程中从超基性岩中萃取。     

动力作用下砂土的残余体变及其时域连续模型

通过对砂土动力剪切荷载作用过程中的土骨架的弹性和塑性分析,研究了土骨架接触面部分可能发生的弹性恢复和永久变形以及破碎引起的最剧烈的塑性变形;并且,提出了可以通过液化前后颗粒粒径的质量百分含量的对比试验,来验证破碎模型的合理性;为进行砂土动力非线性变形和液化的数值模拟,结合砂土的剪切非线性的本构,总结了更为简化的时域连续的函数经验公式,使得在时域内进行土壤动力特性和动力非线性反应分析,以及用剪胀性理论解释动力液化和变形问题易于进行。     

地下硐室锚注围岩的变形分析

地下硐室工程加固后围岩存在着继续位移。通过对工程实例的现场实测和大量测定结果进行统计分析,初步掌握了地下硐室工程破碎围岩加固后的岩体位移存在着方向变异性、破坏周期性和速度差异性。变形过程可分为急剧变形、调整变形和缓慢变形3个阶段。在一定的地压条件下,岩性和构造弱面决定着岩体位移的方向、速度和破坏周期。围岩加固后的位移在调整变形阶段可能改变位移方向,注浆加固岩层比未加固岩层的累计位移量小、但每次破裂的位移量大,破坏周期要短。及时锚注,滞后补注,分步加固是充分利用围岩自稳性,加强破碎围岩长期强度的最佳动态支护技术。