湘西铁路沿线红层边坡工程地质研究

地处湘西山区的湘黔、焦柳铁路沿线分布众多的红层边坡。因其工程地质条件的特殊性,边坡灾害时有发生,严重影响了列车的安全运行。文章首先对这一地区红层的工程地质特性进行研究,在此基础上,对边坡破坏形式、规律、机理等进行深入探讨。研究表明:分布在湘西铁路沿线的红层具有岩性多变、软硬互层、浸水崩解、遇水软化、结构面众多及泥化软弱夹层发育等工程特性;红层边坡变形破坏的主要形式有风化剥落、坡面变形、崩塌落石和顺层滑坡等。文章通过湘西湘黔、焦柳铁路沿线12处较大红层路堑滑坡的调查及综合分析,得出这一地区红层路堑滑坡形成的基本规律并根据滑坡体物质及滑动面特征对其进行了分类。分析了该地区红层滑坡的形成机理并提出红层边坡地质灾害的防治措施。     

湘西要坝洞沉积堆积特征及形成时代

要坝洞在保靖县城北5km,是有旅游和科研价值的洞穴。洞穴发育在保靖-复兴断裂带的裂隙破碎构造控制的白云岩、白云岩化灰岩残体中,是断面陡转缓地段的垂向洞穴,成洞原因与所处的特定地质构造环境有关。在阐述洞穴形成特征的基础上,详细论述了洞穴沉积物及其相关性。洞穴碎屑沉积、次生化学沉积类型齐全,组成高、中、低三个沉(堆)积台面,构成多期(次)沉(堆)积的伴生共存组合体,展示洞穴及其沉积特征和过程。笔者进一步完善了次生化学沉积的成因分类,认为壁流石、钟乳石、石笋、石柱聚集匹配,构成景点,具有旅游观赏价值。同时,选择具有代表性的1号石笋进行同位素测年和综合研究,以其完好的沉积旋回、结构构造特征,显示3～1万a间的冰期气候沉积特征,其冷暖气候转(突)变标志明显。在洞穴及其沉(堆)积综合研究的基础上,根据洞穴沉(堆)积、洞内外新近系、古近系、白垩系的伴生沉积、储存关系,判断要坝洞形成于白垩纪前后。     

湖南省湘潭市地下水质量现状与保护措施

通过对湘潭市区地下水13年监测资料的系统分析与综合研究，将工作区中地下水划分为白垩系岩溶水与第四系孔隙水两类。并对两类地下水水质进行了评价，其中某些元素已有超标现象，总体可达到饮用水标准，最后提出了相应的保护措施。     

湖南宝山多金属矿田构造控矿特征

宝山多金属矿田由四个大型矿床组成。主要控矿条件包括地层、构造和岩浆岩。矿床的空间分布范围、规模与构造有关。褶皱与断裂的组合构造体系控制了矿床的空间定位，构造型式及其构造作用方式控制了矿体的产状与形态。     

GEOCHEMICAL CHARACTERISTICS OF THE EARLY MESOZOIC GRANODIORITES AND THEIR TECTONIC IMPLICATIONS

The early Mesozoic granodiorites (ca. 165 Ma) in the northeastern Hunan Province (NEH) have SiO2=65.4-69.65%, K2O/Na2O=0.95-1.38 and K2O Na2O＞6%, A/CNK=0.96-1.13 and belong to metaluminous high-K calc-alkaline series. They are characterized by LREE and LILEs enrichment, and HFSE depletion with slightly negative Eu anomalies (Eu/Eu*=0.62-0.90). The initial 87Sr/86Sr ratios are in range from 0.711458 to0.717461, and εNd values vary from -9.4 to -12.3, distinct from those of the contemporaneous granodiorites mantle-derived from the Southeastern Hunan Province (SEH) (87Sr/86Sr(i)=0.707962～0.710396, εNd(t)=-6.98～-2.30).By contrast, such signatures are roughly similar to those of the neighboring other Mesozoic granitic plutons (Eu/Eu*=0.30-0.70; 87Sr/86Sr ＞0.710; εNd = -12 to -16) in South China Block (SCB), which have been interpreted as the remelting products of Precambrian basement. The Proterozoic lower-middle crust is an important contributor to the petrogenesis of these early Mesozoic granodiorites in the NEH. An intracontinental extension setting is present in the northeastern Hunan Province at that time due to the demand of enough thermal transfer.     

Numerical modeling of the formation of Indo-Sinian peraluminous granitoids in Hunan Province: Basaltic underplating versus tectonic thickening

The genesis of Indo-Sinian granitic plutons with peraluminous and potassium-rich affini-ties from Hunan Province, China has been investigated by numerical modeling using the numericalcode FLAC. On the basis of the regional geological evolution in South China, we employed a real-istic numerical model in an attempt to unravel the influences of basaltic underplating and tectoniccrustal thickening on the crustal anatexis. Heat production derived from basaltic underplating (e.g.ca. 220 Ma gabbro xenoliths) can result in dehydration melting of fluid-bearing minerals in crustalrocks such as gneisses and metapelites, but its effect is limited in a relatively short time span (5-15 Ma) and on a small scale, Accordingly, it is very difficult for basaltic underplating to generate thelarge-scale Indo-Sinian granitic bathliths unless voluminous mafic magmas had been underplatedat the lower/middle crust during this period. Alternatively, crustal thickening induced by tectoniccompression can also lead to geothermal elevation, during which the temperature at the boundarybetween lower and middle crusts can be up to or greater than 700℃, triggering dehydration melt-ing of muscovite in gneiss and metapelite. The proportion of melts from muscovite-induced dehy-dration melting is close to critical melt percentage (≥20%) once the thickening factor reaches 1.3.These melts can be effectively transferred to the crust-level magma chamber and form large-scalegranitic batholiths. In combination with the Indo-Sinian convergent tectonic setting in South Chinaas well as sparse outcrops of contemporary mafic igneous rocks, we consider that tectonic crustalthickening is likely to be the predominant factor controlling the formation of the Indo-Sinian per-aluminous and potassium-rich granitoids in Hunan Province.     

湖南慈利晚二叠世长兴期珊瑚礁白云石化及其成岩环境

笔者对近期在湖南慈利发现的长兴期珊瑚礁的白云石化作用及成岩环境进行了研究。通过对礁灰岩白云石化的分布、岩石结构构造、微量元素和碳、氧稳定同位素成分的测试研究,对白云石化的环境进行了分析。主要有:①潮上蒸发形成的高盐度交代白云石化;②深埋藏高盐度热水条件下白云石化;③区域抬升埋藏变浅,大气水渗入淡化的热水条件下发生的白云石化。据各类白云石化在礁岩成岩序列中的位置,从早到晚分别命名为Ⅰ、Ⅱ、Ⅲ3个世代,并分析了埋藏白云石化的物源,建立了Ⅱ、Ⅲ两个世代埋藏白云石化的概略模式。最后通过实例说明了研究礁岩埋藏白云石化作用对油气、铅锌矿产勘探的实用意义。     

金鸡岭岩体北外带富铀成矿构造地球化学特征及构造成矿模式探讨

金鸡岭岩体北外带不仅存在良好的铀成矿地质条件，而且还具有富大铀矿的形成条件。构造控制占有重要而独特的地位。通过对含矿断裂带元素分带性研究，总结出铀矿体部位的元素组合特征：Ba,P,Co,Ni，V为铀矿床原生晕前缘元素组合，Zn,Cu为近矿指示元素组合，Mo,Sn,As,Sb为铀矿床尾部矿根元素组合。U，Pb,Cr,Be为铀矿体中组合元素。建立了本区铀矿构造地球化学成矿模式。     

湖南省韧性剪切系统基本特征

河南省的地壳结构是不均一的。它的基本特征是以雪峰弧形韧性剪切带和其它几条NE、NW向的韧性剪切带与菱形弱应变区有规律的组合。这些大型韧性剪切带都是不同尺度的构造边界，对它们的深入研究有助于省内某些重大基础地质问题的解决。 通过对雪峰弧形和永州－株洲NE向韧性剪切带较详细的研究，指出在中浅变质岩区，强直面理化带是韧性剪切带的基本特征之一。     

湖南省矿产资源形势与发展战略问题探讨

湖南省矿产资源比较丰富，有色金属及非金属矿产具有明显优势，但矿产资源形势严峻，保有储量不足，难选治、低品位、共伴生矿多，开发利用难度大，地勘体制改革滞后。矿产资源自给能力明显下降，且矿山数量多、规模小、利用效率低、深加工落后、矿山环境问题严重。应从建立多元化的矿产资源供应体系、调整能源结构、开展科技攻关、改善矿业开发的生态环境等方面实施一系列战略转变，采取建立矿产资源规划体系、建立矿产勘查基金、改善矿业投资环境、提高矿山地质环境保护水平等政策措施，实现湖南矿业的可持续发展。