Petrology and geochemistry of the ultramafic–mafic Mawpyut complex,Meghalaya: a Sylhet trap differentiation centre in northeastern India

The present article describes, for the first time, petrological and geochemical details of the Mawpyut differentiated complex which is related to the Sylhet trap located at Jaintia Hills district, Meghalaya, northeastern India. The Mawpyut complex occurs as an arcuate body that intrudes into the surrounding Shillong Group rocks. The complex in general contains ‘ultramafic’ and ‘mafic’ rocks, as well as minor syenitic veins that postdate the main units. The lithotypes correspond to cumulate and noncumulate units. The cumulate unit is represented by olivine clinopyroxenite, clinopyroxenite, plagioclase‐bearing ultramafic, olivine gabbronorite, mela‐gabbronorite, melagabbro, orthopyroxene gabbro, and gabbro, all with a pronounced cumulus texture. The noncumulate unit is marked by gabbro, monzonite, monzodiorite, and quartzsyenite. The use of several major and trace element variation diagrams suggests that magmatic differentiation led to the formation of cumulate and noncumulate units. In chondrite‐normalized REE diagrams the cumulate rocks show flat LREE and MREE patterns and a moderate positive Eu anomaly (in plagioclase‐bearing ultramafics) due to plagioclase cumulation. The rocks of the noncumulate unit show a strongly fractionated REE pattern and no Eu anomaly. The noncumulate mafic rocks are geochemically comparable to high‐phosphorous/high‐titanium basalts (HPT) indicative of low pressure fractional crystallization. In a primitive mantle‐normalized multielement diagram some of the cumulate rocks show pronounced negative anomalies for K and P, indicating anorogenic mafic magmatism in a within‐plate setting. The rocks of the noncumulate unit show a slight negative anomaly for Yb and a Nb–Ta trough, indicating a subduction‐related signature that perhaps is inherited from subducted sedimentary rocks incorporated during crustal contamination of the derived magma (left after crystal cumulation) with country rocks. Various trace element ratios for the cumulate mafic rocks indicate parent EMI/EMII/HIMU sources with a very limited crustal signature. The noncumulate mafic rocks (corresponding to the derived evolved magma) indicate EMI/EMII/HIMU sources with a pronounced crustal contamination. The Sr–Nd isotopic compositions of the Mawpyut samples typically plot in the continental flood basalt field, with an affinity to the EMII source. The isotopic compositions of the noncumulate rocks also clearly indicate crustal contamination. We suggest that partial melting (involving garnet in the residue) of the enriched mantle source EMI/EMII/HIMU could have derived the parental melt; this melt, in turn, underwent assimilation and fractional crystallization to produce the variety of cumulate‐noncumulate lithologies of the Mawpyut complex. Copyright © 2013 John Wiley & Sons, Ltd.     

高精度地表油气化探技术的发展及应用--以济阳凹陷垛石桥地区土壤酸解烃为例

酸解烃技术是油气化探的一个重要方法,在常规的油气化探中被普遍应用,然而多解性一直影响其应用效果。本文选择济阳凹陷垛石桥地区作为研究区,利用改进的酸解烃技术,分析研究区已知背景区和产油气区土壤中的酸解烃含量及其碳同位素特征,以验证改进酸解烃技术在复杂含油气区块油气化探工作中的有效性,为油气化探提供高精度的技术方法。研究结果表明,垛石桥地区地表土壤酸解烃中甲烷的含量受干扰因素较多,与下伏油气藏没有明显的对应关系;而乙烷和丙烷等重烃含量与下伏油气藏的对应关系较好,可以较好地揭示深部油气运移的贡献。另外,该地区土壤酸解烃的组成特征指示其深部油气源以油藏为主,部分为凝析油藏,与实际地质情况较为吻合,表明改进的酸解烃技术可以作为复杂含油气区块指示深部油气藏的有效化探方法。     

超前侧喷绳索取心钻具的研制

[摘 要]针对破碎、软弱等复杂地层岩心采取率低的问题,本文通过无泵接手、岩心抓取机构和超前侧喷钻头的设计与结合,研制了一套超前侧喷绳索取心钻具;该钻具是一种基于普通绳索取心钻具及无泵反循环钻具设计的新型钻具,能实现孔内钻井液的局部反循环并改变孔底冲洗液流向,从而达到排粉及提高岩心采取率的目的;现场试验表明,超前侧喷绳索取心钻具能够实现破碎、软弱等难取心地层的正常钻进,试验孔段岩心采取率为94%,大幅度提高了岩（矿）心的采取率。     

河北涞源木吉村铜矿ZK6801孔深孔绳索取心钻进体会

结合河北涞源木吉村铜矿ZK6801孔深孔绳索取心钻进实践,总结了金刚石绳索取心钻探工艺在地层复杂的深孔钻探施工的几点经验和体会,着重论述了泥浆护壁堵漏、水泥浆护壁以及套管护壁的应用原则。     

御道口油页岩矿区钻井液的研究与实践

油页岩矿区地层结构复杂,钻孔施工中常有坍塌、掉块、缩径、钻井液漏失等现象发生,易造成埋钻、卡钻、烧钻等事故,且取心困难。通过综合分析并进行实验室试验研究,选择对御道口油页岩地层有较好抑制性的钻井液配方,在生产中选择正确的配制方法并保持好钻井液的性能。通过施工验证,取得了较好的施工效果和经济效益,并收集了大量经验数据,为今后在类似矿区钻探施工提供了技术支撑。     

基于LiDAR点云的复杂钢结构模型重建

传统的基于全站仪等单点测量技术难以获取钢结构整体信息,且测量速度慢、模型重建精度低。针对此问题,本文将三维激光扫描技术应用于钢结构模型重建领域,提出了基于LiDAR点云的复杂钢结构模型重建方法。首先,基于标靶球和钢结构面信息实现多测站点云的高精度配准,并通过半径滤波算法去除噪点,以得到完整的激光点云数据;然后,对复杂钢结构单体模型进行分割,以实现各个部件的模型重建;最后,根据现场实测数据对重建的三维模型进行精度评估。试验结果表明,基于该方法得到的模型精度较高,与实际尺寸差值均小于1 cm,为复杂钢结构的三维模型重建提供了有效解决方案。     

COVID-19期间国家关系交互网络时空分析研究

COVID-19疫情不断蔓延为国际政治、外交关系等带来深刻影响。目前基于复杂网络方法的国际关系研究较少考虑节点的空间属性,难以探索国际关系的动态演化模式及其空间分布特征。该文提出一种结合时间序列聚类与空间统计的国家关系交互网络演化模式探测方法。基于2020年1月-2021年3月的GDELT数据构建国家关系交互网络,基于节点的演化特征,应用K-means聚类算法将节点划分为6种类型,结合局部连接统计方法分析节点演化模式的空间分布特征。研究表明:面对疫情冲击,各国为控制疫情蔓延倾向于参与合作交互事件;国家关系交互网络中的不同时序演化模式总体按照节点的点度中心性强度由高到低分布;疫情防控期间网络中始终处于边缘地位的节点在空间分布上呈现聚集特征,而核心节点空间分布较分散。通过研究网络节点的时序演化模式及空间分布特征可为公共卫生危机事件期间国际关系与地缘政治研究提供新思路,对于危机事件期间制定外交政策与应对策略具有一定参考价值。     

U–Pb ages of detrital zircons within the Inthanon Zone of the Paleo-Tethyan subduction zone,northern Thailand: New constraints on accretionary age and arc activity

U–Pb dating of detrital zircons was performed on mélange-hosted lithic and basaltic sandstones from the Inthanon Zone in northern Thailand to determine the timing of accretion and arc activity associated with Paleo-Tethys subduction. The detrital zircons have peak ages at 3400–3200, 2600–2400, 1000–700, 600–400, and 300–250 Ma, similar to the peaks ages of detrital zircons associated with other circum-Paleo-Tethys subduction zones. We identified two types of sandstone in the study area based on the youngest detrital zircon ages: Type 1 sandstones have Late Carboniferous youngest zircon U–Pb ages of 308 ± 14 and 300 ± 16 Ma, older than associated radiolarian chert blocks within the same outcrop. In contrast, Type 2 sandstones have youngest zircon U–Pb ages of 238 ± 10 and 236 ± 15 Ma, suggesting a Middle Triassic maximum depositional age. The youngest detrital zircons in Type 1 sandstones were derived from a Late Carboniferous–Early Permian ‘missing’ arc, suggesting that the Sukhothai Arc was active during sedimentation. The data presented within this study provide information on the development of the Sukhothai Arc, and further suggest that subduction of the Paleo-Tethyan oceanic plate beneath the Indochina Block had already commenced by the Late Carboniferous. Significant Middle Triassic arc magmatism, following the Late Carboniferous–Early Permian arc activity, is inferred from the presence of conspicuous detrital zircon U–Pb age peaks in Type 2 sandstones and the igneous rock record of the Sukhothai Arc. In contrast, only minimal arc activity occurred during the Middle Permian–earliest Triassic. Type 1 sandstones were deposited between the Late Permian and the earliest Triassic, after the deposition of associated Middle–Late Permian cherts that occur in the same mélanges and during a hiatus in Sukhothai Arc magmatism. In contrast, Type 2 sandstones were deposited during the Middle Triassic, coincident with the timing of maximum magmatism in the Sukhothai Arc, as evidenced by the presence of abundant Middle Triassic detrital zircons. These two types of sandstone were probably derived from discrete accretionary units in an original accretionary prism that was located along the western margin of the Sukhothai Arc.     

复杂地质条件下桩基础施工难点分析

随着北京地区基坑深度及单桩承载力要求的提高,基础施工面在不断向下移动,桩深度也在不断加深,使得施工情况也越来越复杂,如承压水的处理,相对水位的变化、地层的变化、施工设备的选择、场地的局限性等,针对这些问题,以北京地区某工程深桩基施工为例,介绍了承压水条件下,砂层、粉粘土层和卵石层多层互层复杂地质条件下的深桩基现场施工设备的选择和现场管理工作。介绍施工过程中的一些难点、要点及其解决方法。本研究可为类似工程提供参考。     

汶川地震断裂带科学钻探三号孔（WFSD-3）事故处理与认识

WFSD-3孔因地层破碎、缩径,不可预知因素多,发生多起孔内事故,通过对钻铤脱扣、下套管卡钻、埋钻等不同事故原因分析、事故处理,对WFSD-3孔施工工艺做出了改进与调整,总结了对科学钻探孔事故预防与处理的经验体会。