Hydrogeology of thermal waters in Viterbo area, central Italy

A conceptual hydrogeological model of the Viterbo thermal area (central Italy) has been developed. Though numerous studies have been conducted on its geological, geochemical and geothermal features, there is no generalized picture defining the origin and yield of the hydrothermal system. These latter aspects have therefore become the objectives of this research, which is based on new hydrogeological and geochemical investigations. The geological setting results in the coexistence of overlapped interacting aquifers. The shallow volcanic aquifer, characterized by fresh waters, is fed from the area around the Cimini Mountains and is limited at its base by the semiconfining marly-calcareous-arenaceous complex and low-permeability clays. To the west of Viterbo, vertical upflows of thermal waters of the sulphate-chloride-alkaline-earth type with higher gas contents, are due to the locally uplifted carbonate reservoir, the reduced thickness of the semiconfining layer and the high local geothermal gradient. The hot waters (30–60°C) are the result of deep circulation within the carbonate rocks (0.5–1.8 km) and have the same recharge area as the volcanic aquifer. The upward flow in the Viterbo thermal area is at least 0.1 m³/s. This flow feeds springs and deep wells, also recharging the volcanic aquifer from below.     

Secular variations of the upper crust composition: Implication of geochemical data on the Upper Precambrian shales from the Southern Urals western flank and Uchur-Maya region

In the mid-1980s, it was concluded based on geochemical study that Th, Sc, La concentrations and ratios Th/Sc, La/Sc and Eu/Eu* did not wary significantly in the post-Archean time. It was impossible to judge about compositional variations of upper crust during the Riphean and Vendian, because data of that time characterized a limited number of samples from the post-Archean basins of Australia, New Zealand, and Antarctic. Considered in this work are variations of Eu/Eu*, LREE/HREE, Th/Sc, and La/Sc ratios in Upper Precambrian fine-grained siliciclastic rock of the Southern Urals western flank (Bashkirian meganticlinorium) and Uchur-Maya region (Uchur-Maya plate and Yudoma-Maya belt). As is established, only the Eu anomaly in the studied siliciclastic rocks is practically identical to this parameter of the average post-Archean shale. Three other parameters plot on the Riphean-Vendian variation curves with positive and negative excursions of diverse magnitude, which do not coincide always in time. It is assumed that these excursions likely mark stages of local geodynamic activity, destruction of pre-Riphean cratons, and progressing recycling of sedimentary material during the Riphean.     

江西省宜春城区地面塌陷特征及防治建议

宜春城区属岗阜低丘地形,分布石炭系-二叠系覆盖型及裸露型碳酸盐岩,占城区面积近70%。浅部岩溶发育,覆盖层厚度一般小于20m,土洞较多,基岩面起伏大,第四系岩性结构复杂,地下水埋藏浅。由于抽采地下水及建筑施工振动等人为因素影响,诱发地面塌陷12处,造成重大经济损失。在城市规划功能布局时应充分考虑地面塌陷的易发程度及场地建设适宜性;应限制诱发塌陷因素的强度,在易发区须严格控制地下水开采,严禁新建开采井;塌陷治理的主要方法有填堵、跨越、灌注、深基础控制抽排水强度、及其它综合治理或避让方法,同时做好灾害的监测预报工作。     

邢台矿区山字型构造的发现及其地质意义

邢台山字型构造位于河北省邯邢煤田内，其前弧向ES突出，脊柱呈ES-WN走向。分别分析了山字型构造脊柱及其东、西翼反射弧构造形迹特征，对研究区找矿具有重要意义。     

Early Proterozoic syn-and postcollision granites in the northern part of the Baikal fold area

Early Proterozoic granitoids are of a limited occurrence in the Baikal fold area being confined here exclusively to an arcuate belt delineating the outer contour of Baikalides, where rocks of the Early Precambrian basement are exposed. Geochronological and geochemical study of the Kevakta granite massif and Nichatka complex showed that their origin was related with different stages of geological evolution of the Baikal fold area that progressed in diverse geodynamic environments. The Nichatka complex of syncollision granites was emplaced 1908 ± 5 Ma ago, when the Aldan-Olekma microplate collided with the Nechera terrane. Granites of the Kevakta massif (1846 ± 8 Ma) belong to the South Siberian postcollision magmatic belt that developed since ～1.9 Ga during successive accretion of microplates, continental blocks and island arcs to the Siberian craton. In age and other characteristics, these granites sharply differ from granitoids of the Chuya complex they have been formerly attributed to. Accordingly, it is suggested to divide the former association of granitoids into the Chuya complex proper of diorite-granodiorite association ～2.02 Ga old (Neymark et al., 1998) with geochemical characteristics of island-arc granitoids and the Chuya-Kodar complex of postcollision S-type granitoids 1.85 Ga old. The Early Proterozoic evolution of the Baikal fold area and junction zone with Aldan shield lasted about 170 m.y. that is comparable with development periods of analogous structures in other regions of the world.     

藏北若拉岗日岩群变质火山岩的基本特征及构造属性

藏北的若拉岗日岩群，因处于拉竹龙-金沙江缝合带南缘，其成生背景及构造属性历来倍受关注。白头山、岗盖日、狮头山等地的若拉岗日岩群主要为一套变质中基性火山岩系，不同地段夹杂大理岩、变质砂板岩、硅质岩、超基性岩等小岩片或块体，分别具有洋岛型、洋脊型及岛弧型火山岩的基本特征，并构成白头山西以岛弧火山岩为主的弧火山岩片，岗盖日以洋脊型变玄武岩为主夹杂硅质岩、超基性岩小岩片而共同组成的蛇绿混杂岩片及白头山、狮头山以洋岛型火山岩为主夹杂碳酸盐岩块体的大洋海山岩片，从而指出该区若拉岗日岩群为一套不同构造属性的火山岩与大理岩、硅质岩、超基性岩等相伴的构造混杂岩，其中既有某大洋的产物，又有某洋岛及陆缘岛弧的产物。     

中国大陆科学钻探工程主孔100～2000 m 放射性产热元素的垂向分布特征及其成因

地球内部放射性产热元素U、Th及K(HPE)含量如何随深度的变化而变化是固体地球科学中的一个重要参数,在限定地壳的热和流变学结构、地球化学、岩石和构造模型中起关键性的作用。对HPE深部分布的认识主要来自于对大型花岗岩岩基的研究及对地表热流值和产热率之间关系的模拟,对高压-超高压变质地体的HPE随深度的分布缺乏认识。在苏鲁超高压变质带中实施的中国大陆科学钻探工程届时将提供超过5km的岩心,为确定苏鲁超高压带的HPE结构提供了最好的机会。对CCSD的100～2000m岩心的732块样品详细的放射性产热元素含量的测试及现今产热率计算的初步结果表明:(1)花岗质片麻岩具有最高的产热率,平均为1665×10-11W/kg;(2)副片麻岩(变沉积岩)具有中等的产热率,为994×10-11W/kg;(3)金红石榴辉岩及石榴石橄榄岩具有最低的产热率,为17×10-11～20×10-11W/kg;(4)放射性产热元素的浓度及相应的产热率随岩性的变化而变化,呈现阶梯状的分布特征。产热率随深度的变化特征表明CCSD主孔中的HPE三明治结构。该结构可能代表着高压-超高压变质地体中的典型HPE结构,比大型花岗岩岩基的HPE结构更复杂,与传统的HPE指数衰减分布模式不吻合。CCSD主孔中所揭示的三明治式HPE结构是大陆被动陆缘中的基性及超基性岩、沉积岩及花岗岩在深     

江西彭山锡多金属矿田地质地球化学特征研究

彭山锡多金属矿田位于长江中下游的九瑞地区，是近年来发现的一个以富锡、铅、锌矿产为主的大型矿田。以黑云母二长花岗岩与二云母碱长化岗岩组成的彭山隐伏岩体为中心，各类金属矿床呈“晕圈式”分布。矿床的形成分为2个成矿期共7个阶段，通过对彭山岩体、典型矿床及围岩中的硫同位素、铅同位素、包裹体及稀土资料进行分析，反映出燕山晚期钙碱性花岗岩体的缦位与多金属矿床的形成有着密切的联系，岩浆活动为本区提供了大量的成矿物质。     

江西省定南县滑坡形成条件分析

江西省定南县滑坡较为发育，1990～2002年，全县共发生滑坡283处，其规模一般较小，但造成的损失大。滑坡均由降雨诱发，4～6月份降雨量较大、多暴雨，该段时间滑坡较为多发；除此以外，影响滑坡形成的因素还有地形地貌、岩土类型、地质构造、岩土结构类型、人工切坡等。江西省定南县主要为中低山与丘陵地形，山坡坡度较大；岩土类型主要为岩浆岩、变质岩，岩石较为破碎，残坡积层与强风化层厚度大；断裂构造较为发育；居民大量挖山建房，形成大量的人工高陡边坡；这些因素为滑坡的形成提供了必要条件。