Trace Element Geochemistry of Magnetite from the Fe(-Cu) Deposits in the Hami Region, Eastern Tianshan Orogenic Belt, NW China

Laser ablation–inductively coupled plasma–mass spectrometry(LA–ICP–MS) was used to determine the trace element concentrations of magnetite from the Heifengshan, Shuangfengshan, and Shaquanzi Fe(–Cu) deposits in the Eastern Tianshan Orogenic Belt. The magnetite from these deposits typically contains detectable Mg, Al, Ti, V, Cr, Mn, Co, Ni, Zn and Ga. The trace element contents in magnetite generally vary less than one order of magnitude. The subtle variations of trace element concentrations within a magnetite grain and between the magnetite grains in the same sample probably indicate local inhomogeneity of ore–forming fluids. The variations of Co in magnetite between samples are probably due to the mineral proportion of magnetite and pyrite. Factor analysis has discriminated three types of magnetite: Ni–Mn–V–Ti(Factor 1), Mg–Al–Zn(Factor 2), and Ga– Co(Factor 3) magnetite. Magnetite from the Heifengshan and Shuangfengshan Fe deposits has similar normalized trace element spider patterns and cannot be discriminated according to these factors. However, magnetite from the Shaquanzi Fe–Cu deposit has affinity to Factor 2 with lower Mg and Al but higher Zn concentrations, indicating that the ore–forming fluids responsible for the Fe–Cu deposit are different from those for Fe deposits. Chemical composition of magnetite indicates that magnetite from these Fe(–Cu) deposits was formed by hydrothermal processes rather than magmatic differentiation. The formation of these Fe(–Cu) deposits may be related to felsic magmatism.     

Provenance, Tectonic Setting and Geochemistry of Ahwaz Sandstone Member (Asmari Formation, Oligo-Miocene), Marun Oilfield, Zagros Basin, SW Iran

The Asmari Formation deposited in the Zagros foreland basin during the OligoceneMiocene. Lithologically, the Asmari Formation consists of limestone, dolomitic limestone, dolomite, argillaceous limestone, some anhydrite(Kalhur Member) and sandstones(Ahwaz Member). This study is based on the analysis of core samples from four subsurface sections(wells Mn-68, Mn-281, Mn-292 and Mn-312) in the Marun Oilfield in the Dezful embayment subzone in order to infer their provenance and tectonic setting of the Ahwaz Sandstone Member. Petrographical data reveal that the Ahwaz Sandstone comprises 97.5% quartz, 1.6% feldspar, and 0.9% rock fragments and all samples are classified as quartz arenites. The provenance and tectonic setting of the Ahwaz Sandstone have been assessed using integrated petrographic and geochemical studies. Petrographic analysis reveals that mono- and poly-crystalline quartz grains from metamorphic and igneous rocks of a craton interior setting were the dominant sources. Chemically, major and trace element concentrations in the rocks of the Ahwaz Sandstone indicate deposition in a passive continental margin setting. As indicated by the CIW′ index(chemical index of weathering) of the Ahwaz Sandstone(average value of 82) their source area underwent "intense" recycling but "moderate to high" degree of chemical weathering. The petrography and geochemistry results are consistent with a tropical, humid climate and low-relief highlands.     

关于郯庐断裂巨大平移问题的商榷

本文以大量地质事实证明郯庐断裂在新生代经历了强烈的水平挤压,中生代则经历了侏罗纪时的水平挤压和白垩纪时的强裂拉张。从古构造和古地理分析,郯庐断裂也未造成过太古界、元古界和古生界地层的明显错移,它们都是受当时的古构造和古地理控制而原地沉积,并非由于郯庐断裂的“巨大平移”才具有现在的布局。郯庐断裂形成于太古代末-元古代初,其后经历了地槽阶段、地台阶段和地洼阶段的漫长演化。不同时期表现出不同的活动特点,但基本上以差异升降和水平挤压及拉张形式为主,未见巨大平移的证据。     

岩石综合物性差异与变化的特征

从岩石物性与化学元素原子结构的关系出发，从密度、弹性、电性和放射性等诸方面，论述了岩石综合物性差异与变化的特征；并结合实例，得出岩石综合物性参数发生变化反映了组成岩石的原子、分子、矿物和结构发生了变化，且各参数之间具有某种相关性的结果．      

抗滑桩内力计算“K”法的改进与应用

对传统的抗滑桩内力计算“K”法作了一些改进,如建立了滑动面上下统一的坐标系,将桩视为一个整体进行考虑,通过合理的假定,保证了桩身在滑动面处内力和位移的连续性,同时,采用名的MATLAB数学软件设计了“K”法的计算程序,适用于滑坡推力和桩前滑体抗力分布的各种形式以及抗滑桩为刚性桩和弹性桩的情况,实例计算结果表明,较之传统的查表法,该方法有效地提高了抗滑桩内力和位移计算速度和精度,同时可得到理想的可视化计算结果,有助于抗滑桩结构的优化设计。     

新构造运动在塔里木盆地演化中作用

在第四纪以来的新构造运动的影响下,塔里木盆地逐渐向封闭的干旱盆地演化。由于波动式的新构造运动在每阶段表现的形式有差异,因而盆地的演化也相应表现出明显的阶段性。该盆地新构造运动大致经历了上新世末—早更新世、早更新世末—中更新世以及晚更新世三个阶段,其中以早更新世末的一次构造运动对盆地的地貌影响最大。新构造运动是由印度板块和欧亚板块挤压引起的,故塔里木盆地与青藏高原的演化阶段在时间上大致吻合。     

论找矿勘查的风险性和降低风险的预测性勘查战略

找矿勘查的高风险性表现在找到可赢利矿床的成功率低和找矿发现的成本越来越高,这不仅影响了矿业经济的发展,也影响了公众对地球科学的认识。根据国际找矿勘查的一些统计资料和实例分析了造成找矿勘查高风险性的原因,提出降低风险的预测性勘查战略。区域地质背景、成矿作用的复杂性和勘查者所具有的知识、思维能力、技术手段的局限性等客观因素使找矿勘查的风险不可避免,但不少找矿勘查的失败是由勘查者在资料使用、观察、思维等方面的主观失误造成的。勘查者可以通过增加尝试的次数来获取成功,更可取的是通过提高矿床预测的准确度,以预测性勘查促找矿发现,进而降低找矿勘查的风险。     

高岭石的胶体稳定性与其电荷零点的关系

高岭石的胶体稳定性与其表面电荷性质有密切关系。高岭石既带有正电荷又带有负电荷,高岭石与腐殖酸复合可增加负电荷,降低电荷零点,增加粒间斥能,提高了它的胶体稳定性。     

元素活动态测量法在鄂尔多斯盆地砂岩型铀矿勘查中的应用

常规化探方法勘查砂岩型铀矿难以奏效。应用深穿透地球化学方法系列中的元素活动态测量法在鄂尔多斯盆地砂岩型铀矿上的试验结果表明,几种U元素活动态在矿体上方都有异常出现,特别是其中的粘土吸附态U含量级别高、异常衬度大。因此,土壤粘土吸附态U测量法是本区化探找铀矿的有效方法;取样深度和取样粒级分别以60～90cm和-120目为宜;采用400m的取样点距基本不影响本区砂岩型铀矿的找矿效果。在盆地东北部应用土壤粘土吸附态U测量法预测了3个有利地段,并在其中1个地段的深部发现了较好的铀矿化。     

大别山高压变质杂岩中的硬玉

本文描述了在大别山高压变质杂岩中新近发现的石榴硬玉石英岩的岩石学物质特征。对高压指示性矿物硬玉的物理性质、光学性质、化学成分及结构进行了精确测定和研究。认为石榴硬玉石英岩与柯石英榴辉岩形成于同一高温超高压物理化学条件，硬玉的出现主要受控于原岩特定的化学成分。