青藏高原东缘中更新世伸展作用及其新构造意义

基于区域TM遥感影像资料解译和野外构造地貌调查以及晚第四纪沉积物光释光测年分析,论述了青藏高原东缘复杂地貌边界带晚第四纪伸展构造及其构造地貌特征。结果显示,伸展构造主要见于下列几个构造带:沿南北走向的安宁河谷地、大凉山构造带、若尔盖盆地、岷江断裂带等。其典型的地貌特征表现为充填晚第四纪沉积物的狭窄河谷。根据盆地沉积物的地层时代和年龄推断,正断作用主要发生在中更新世时期,大约起始于早更新世末期(1.2～0.9Ma),结束于中更新世晚期(100～200ka)。晚更新世以来,构造体制转化为走滑—逆冲机制。青藏东缘中更新世伸展构造作用可能与该地貌边界带晚新生代造山后的高原垮塌有关。     

Chronology, Geochemistry and Tectonic Settings of the Hadamiao Granodiorite on the Northern Margin of the North China Platform

<正>The Hadamiao granodiorite,located on the northern margin of the North China platform and acting as the country rock of gold deposits in the Hadamiao region,was formed in the same age and similar tectonic settings with the Hadamiao gold deposit and the large-scale Bilihe gold deposit in the same area.By using the LA-ICP-MS method,the U-Pb age obtained is 267±1.3 Ma,which represents the crystallized age of the granodiorite,and that of the xenolithic zircon is 442.8±5 Ma. Base on the main elements,it exhibits the features of calc-alkaline to high-potassium calc-alkaline series,low silicon,and quasi-aluminous I-type granites,and with high magnesium(Mg~#=0.45-0.57) and high sodium contents(Na_2O/K_2O=0.98-2.29).The SREE values(81.6-110.15 ppm) are relatively low,the fractionations between LREE and HREE are obvious,showing a right-inclined dispersion in the REE distribution diagram.Compared with the primitive mantle,the rock is relatively rich in LREE(La and Ce),LILE(K,Sr,and Th),and intensively depleted in HFSE(Ti,P,Nb and Ta).The ratios of Sr/Y and(La/Yb)_N and the contents of Rb,Nb and Y are relatively low,the Sr values are high (436.35-567.26 ppm),and the Yb contents of most samples are low(1.25-1.8),which indicate the features of typical continental margin arc and adakitic rocks.According to the values ofε_(Nd)(t)(-2.4 to +0.2) and I_(Sr)(0.7028-0.7083),and variations of the La/Sm ratios,the Hadamiao granodiorite was formed from mixing of the thickened molten lower crust and the mantle wedge substances.The rock was related to the southward subduction and accretion of the Paleo-Asia Ocean in the Late Paleozoic, being Late Paleozoic magma of the continental margin arc formed on the basement of the Early Paleozoic accretion complexes,and showing a trend of turning into adakitic rocks,which indicates their great metallogenic(Au) potential.     

灌注桩后注浆单桩竖向极限承载力研究

近年来,后注浆技术得到了广泛的应用。钻孔灌注桩可大大降低建筑物的沉降,并使建筑物的沉降更加均匀,文章介绍后注浆工艺的承载力提高机理及在天津地区的几个工程实例,分析了注浆前后单桩竖向极限承载力对比情况及影响单桩竖向极限承载力的几个因素。     

福建泰宁长兴金矿床地质特征及成因探讨

长兴金矿床主要产于长兴岩体钾长混合花岗岩及其外接触带交溪组变质岩中,矿体受断裂(裂隙带)控制,呈透镜状、不规则脉状分布,综合分析认为交溪组变质岩为初始矿源层,加里东期混合岩化使金在有利构造部位形成初步富集,印支晚期-燕山早期构造-岩浆热液叠加成矿,矿床成因类型为中温热液充填交代型金矿床,其工业类型为破碎带蚀变岩型金矿床。     

中亚地区阿姆河盆地查尔朱、布哈拉阶地构造特征及演化

阿姆河盆地是中亚地区重要的含油气盆地,位于阿姆河北岸的查尔朱阶地和布哈拉阶地为盆地的二级构造单元,其油气资源量占全盆地的一半。油气主要富集于阶地的局部背斜构造和生物礁圈闭中,这些圈闭与该区构造形成演化密不可分。利用常规地质资料,通过精细地层对比和地震资料解释,识别出两个关键界面:侏罗纪末的断拗转换面和早第三纪末的区域角度不整合面,并结合板块构造理论确定了构造变形时期。研究认为,侏罗纪以来两阶地经历了侏罗纪—白垩纪断陷—拗陷期和早第三纪抬升—改造期两个重要演化阶段,形成了上、中、下三大构造层。断陷—拗陷阶段的沉积控制了该区的构造格局;中构造层膏盐层的发育丰富了后期的构造样式。早第三纪—晚第三纪的构造运动使该区构造发生了强烈变革,形成了典型的逆断裂、走滑断裂带和不对称复合背斜构造带。     

Eustatic and tectonic controls on Quaternary Ras Leona marine terraces (Strait of Gibraltar, northern Morocco)

Well-preserved Quaternary staircased marine terraces appear on Ras Leona limestone relief. This is a peculiar sector of the Betic-Rif Cordillera, lying in the four-way junction between the Atlantic and the Mediterranean, and Europe and Africa. The age and altitude correlation of the Ras Leona terraces with travertine-covered lateral equivalent terraces fashioned in the neighbouring Beni Younech area, and comparison with those along the Moroccan Atlantic coasts, would suggest that the Ras Leona terraces were mainly formed by eustatic factors. The importance of the eustasy is supported by further comparisons with Spanish and Moroccan Mediterranean terraces and with different marine terraces developed on passive-margin coasts around the world. A tectonic event occurred mainly during the period between the formation of the Maarifian and the Ouljian terraces (i.e., between 370 and 150 ka). The moderate Quaternary tectonic uplift deduced from the marine terraces and its comparison with uplifted marine terraces developed in active subduction setting disagrees with the model of an active eastwards subduction below the Gibraltar tectonic arc.     

Perched lobe formation in the Gulf of Cadiz: Interactions between gravity processes and contour currents (Algarve Margin, Southern Portugal)

The Gulf of Cadiz is swept by the strong saline Mediterranean Outflow Water (MOW). On the Algarve Margin (South Portugal), this current has constructed fine-grained contourite drifts. This margin is dissected by the Portimao Canyon and three short channels that only incise the upper slope, and are absent on a terrace located at mid-slope depths along the Algarve Margin. High-resolution seismic profiles and sediment cores highlight the original architecture of the sedimentary deposits on this terrace. Coarse-grained lenticular chaotic bodies formed during major relative sea-level lowstands are intercalated within the drift. The lobate shape and sandy nature of the lenticular chaotic bodies and their location at the mouths of the three short channels suggest they are gravity-generated deposits that are perched on the middle continental slope.In the Gulf of Cadiz, the interaction between contour current and gravity processes is strongly controlled by climatic variations and relative sea-level changes during the late Quaternary. During cold periods when sea-level was low, erosion intensified on the continental shelf and the deepest part of MOW was active. Sediment was transported downslope through the channels and deposited on sedimentary lobes perched on the mid-slope terrace. During warm periods when relative sea-level was high, the supply of sediment from the shelf was shut off and the shallowest part of MOW was more active. Contourite drifts fill the channels and bury the sandy lobes.     

综合物探技术在煤系上覆薄硬岩矿区的应用初探——以山西潞安集团司马矿区为例

山西潞安集团司马矿区东高西低,西部延至长治盆地,矿区水系发育。主采3#煤层埋藏较浅,层位稳定。新生界不整合于下伏基岩之上,厚度变化较大,属典型的薄硬岩煤矿区。为准确提供矿区煤炭开采上限的地质依据,采用了综合勘探技术,其中利用三维地震勘探技术追踪新生界底面反射波及第四系"天窗"位置,利用直流电法与瞬变电磁法提供电性分层,并对其解释结果进行相互印证。勘探实例表明,三维地震勘探、电法勘探与钻探的综合运用不仅可解决薄硬岩煤矿区新生界厚度、含水层富水性及第四系缺失等问题,还可提供新生界含水层与基岩含水层之间的水力联系、制约因素等资料。     

嵊泗海域地下淡水资源开发利用方案评价

在上海南汇至浙江省嵊泗列岛之间的长江古河道海底延伸部分,形成于早更新世地层中,蕴藏着丰富的优质地下水资源,是嵊泗岛理想的供水水源。根据"嵊泗二井"勘探资料,在研究海域长江古河道发育规律以及海域地下水赋存规律的基础上,运用MODFLOW软件对嵊泗海域第四系第Ⅰ、Ⅲ含水层,用两种开发方案进行数值模拟。结果表明,在研究区域内可以获得9×104m3/d的地下水资源量;在该海域可以建立永久性的水源地。     

钻探岩心高光谱数据管理与分析系统的构建

钻探岩心编录一直是地质勘探中至关重要的环节,高光谱探测技术的发展为岩心分析提供了一种新的编录技术。为了使获得的岩心资料能永久保存且便于使用和分析,笔者开发了钻探岩心高光谱数据管理与分析系统。通过该系统使用者能方便管理、查看钻探岩心数据,快速提取、分析岩心矿物的光谱特征,为后期矿物的识别奠定了基础。