Geological characteristics and the origin of ore-forming materials of(Laozhaiwan gold deposit, Yunnan Province

"Golden triangle"area bordered on Yunnan-Guizhou-Guangxi was one of the most important Carlin-type gold deposits concentration areas.Deep understanding of Carlin-type gold deposits in Guizhou and Guangxi Province had reached through several decades studies,but geological environment was very complex in the southeastern Yunnan,and Carlin-type gold deposits produced in the southeastern Yunnan were different from that of America,few studies were taken there.Based on a large number of field work,studies on the geological characteristics combining with geochemistry characteristics were taken,and analysis the genesis of Laozhaiwan gold deposit.The types of alteration in Laozhaiwan gold deposit were mainly silicification and pyritization,and Gold grade was high when silicification and pyritization were both occurred.It could be caculated that fluid density(g/cm3)varied from 0.7 to 4.9,salinity varied from 0.76%to 0.95%and ore-forming pressure(Pa)varied from 1.81×105 to 49.96×105 according to fluid inclusion test results,showed that Laozhaiwan gold deposit was hypabyssal hydrothermal deposit in low temperature and low salinity.According to composition of fluid inclusion analysis,combining with H-O isotope,made theδD-δ18O figure,showed that the fluid of the deposit rooted in formation water and mixed with meteoric waters later.

Adverse Geology Identification Through Mineral Anomaly Analysis During Tunneling:Methodology and Case Study

Accurate and effective identification of adverse geology is crucial for safe and efficient tunnel construction.Current methods of identifying adverse geology depend on the experience of geologists and are prone to misjudgment and omissions.Here,we propose a method for adverse geology identification in tunnels based on mineral anomaly analysis.The method is based on the theory of geoanomaly,and the mineral anomalies are geological markers of the presence of adverse geology.The method uses exploration data analysis(EDA)to calculate mineral anomaly thresholds,then evaluates the mineral anomalies based on the thresholds and identifies adverse geology based on the characteristics of the mineral anomalies.We have established a dynamic expansion process for background samples to achieve the dynamic evaluation of mineral anomalies by adjusting anomaly thresholds.This method has been validated and applied in a tunnel excavated in granite.As shown herein,in the tunnel range of 142+800–142+860,the fault F37 was successfully identified based on an anomalous decrease in the diagenetic minerals plagioclase and hornblende,as well as an anomalous increase in the content of the alteration minerals chlorite,laumonite,and epidote.The proposed method provides a timely warning when a tunnel enters areas affected by adverse geology and identifies whether the tunnel is gradually approaching or moving away from the fault.In addition,the applicability,accuracy,and further improvement of the method are discussed.This method improves our ability to identify adverse geology,from qualitative to quantitative,and can provide reference and guidance for the identification of adverse geology in mining and underground engineering.

Geological Anomaly of China

Geological anomaly is a geological body or geological body combination different from its surroundings in composition, structure, or genetic sequence. If there is a value (value interval ) that works as a valve representing the background field, exceeding or lower than the valve value,it is called a geological anomaly. Geological anomalies can be divided into high geological anomaly and low geological anomaly .The former shows the area that is more complex in composition, Structure or genetic sequence than its surroundings; while the latter just gives an opposite indication, i. e. much simpler. According to their distribution and delimitation markers, geological anomalies can be classified into (1)global geological anomaly; (2)regional geological anomaly; (3) local geological anomaly; (4) minor geological anomaly and (5)micro-geological anomaly .The methods for delimiting geological anomalies include (1)crustal elevation-subsidence coefficieat (G value ) determination; (2) geological complex coefficient (C value ) determination; (3) entropy (H value ) determination; (4) geological similarity coefficient (S value ) determination and (5 ) geological correlation coefficient (R value ) determination. As the result of the movements of Eurasian, Pacific and Indian Plates, the Chinese geological anomalies, including 11 regional ones and 32 main local ones, most Paleozoic in age, are distributed in strip on the margin or the outer and inner folded zones in the east and west arcs of the block symmetric arc tectonic system (BSATS), which controls the distribution of various minerals in China. Thus, geological anomaly theory is of great significance in searching for large, super-large and very large ore deposits.

Theory of Geological Anomaly in Remote Sensing

Geological anomaly is geological body or complex body with obviously different compositions, structures or orders of genesis as compared with those in the surrounding areas. Geological anomaly, restrained by the geological factors closely associated with ore forming process, is an important clue to ore deposits. The geological anomaly serves as a geological sign to locate ore deposits. Therefore, it is very important to study how to define the characteristics of geological anomaly and further to locate the changes in these characteristics. In this paper, the authors propose the geological anomaly based on the remote sensing images and data, and expound systematically such image features as scale, size, boundary, morphology and genesis of geological anomalies. Then the authors introduce the categorization of the geological anomalies according to their geneses. The image characteristics of some types of geological anomalies, such as the underground geological anomaly, are also explained in detail. Based on the remote sensing interpretation of these geological anomalies, the authors conclude that the forecasting and exploration of ore deposits should be focused on the following three aspects: (1) the analysis of geological setting and geological anomaly; (2) the analysis of circular geological anomaly, and (3) the comprehensive forecasting of ore deposits and the research into multi source information.

Geological factors controlling deep geothermal anomalies in the Qianjiaying Mine,China

Here,the geological factors controlling deep geothermal anomalies in mines were studied based on the geotemperature,lithologic thermal conductivity,and related geological data collected from the Qianjiaying Mine,China.A simulation of the change in magma waste heat,conducted using the ANSYS Workbench,revealed the distribution characteristics of geothermal anomalies in this mine and the corresponding geological control factors.The results revealed the following points.(1)First-degree heat hazard level(temperature=31-37℃)occurred in the central and southwestern parts of the mine at an^600-m depth,while second-degree heat hazard level(temperature≥37℃)occurred at an^800-m depth.The geotemperature and geothermal gradient in the southwestern part of the mine were anomalously high.(2)The geotemperatures measured in the mine generally reflected a standard increase with depth,while the geothermal gradient remained unchanged with depth.The geothermal gradient and its average value in the study area were 0.70-4.23 and 2.12C·hm^-1,respectively.(3)A combination of stratum characteristics,geological structure,and groundwater characteristics led to geothermal anomalies in mines;additionally,the waste heat from magma had no significant effect on the geothermal field.

3D modeling of geological anomalies based on segmentation of multiattribute fusion

3D modeling of geological bodies based on 3D seismic data is used to define the shape and volume of the bodies, which then can be directly applied to reservoir prediction, reserve estimation, and exploration. However, multiattributes are not effectively used in 3D modeling. To solve this problem, we propose a novel method for building of 3D model of geological anomalies based on the segmentation of multiattribute fusion. First, we divide the seismic attributes into edge- and region-based seismic attributes. Then, the segmentation model incorporating the edge- and region-based models is constructed within the levelset- based framework. Finally, the marching cubes algorithm is adopted to extract the zero level set based on the segmentation results and build the 3D model of the geological anomaly. Combining the edge-and region-based attributes to build the segmentation model, we satisfy the independence requirement and avoid the problem of insufficient data of single seismic attribute in capturing the boundaries of geological anomalies. We apply the proposed method to seismic data from the Sichuan Basin in southwestern China and obtain 3D models of caves and channels. Compared with 3D models obtained based on single seismic attributes, the results are better agreement with reality.

An Expression for Gravity Generated by an Anomalous Geological Body and Its Application in Bathymetry Inversion

The gravity anomaly and vertical gravity gradient due to anomalous geological bodies are mainly computed by numerical methods,so it is difficult and time-consuming to use the gravity-geological method to invert seafloor topography.This paper addresses this issue by deriving an expression for gravity generated by a cylinder based on a series expansion.The choice of number for terms in the series is estimated by comparing with the numerical method,especially when the depth H=4000m,the accuracy of 1 mGal(1 Gal=10^(-2)m/s^(2))can be achieved when the series are 9.The expressions can be used to establish the relationships between the shape of an anomalous body and the generated vertical gravity and vertical gravity gradient,respectively.Finally,the potential applications of the expressions in inverting seafloor topography are illustrated by synthetic examples.

Using satellite magnetic data to divide geological tectonic units of South China Sea

The South China Sea locates at the convergence center of the Eurasian Plate,the Pacific Plate and the Indo-Australia plate. The Cenozoic seafloor spreading in the South China Sea Basin is an important part of the tectonic evolution of the South China Sea that records information of the continental margin tectonic history and its impact on regional geologic evolution. Magnetic data contains abundant geological structure information from the surface to deep. This paper reports magnetic data of the South China Sea. Through the conventional processing of these magnetic data,we report general results on the regional magnetic anomalies,such as the upward continuation graph,the polar magnetic anomaly map and the magnetic anomaly partition map. The magnetic anomaly field in the South China Sea is divided into eight areas,of which the characteristics are explained,and the tectonic evolution of the South China Sea is preliminarily discussed.

Geological inferences about the upper crustal configuration of the Medellin-Aburra Valley(Colombia)using strong motion seismic records

In regions of complex geology and tectonic assembly, strong motion seismic arrival time records can be used to test the plausibility of existing hypothesis about the origin of lithological and tectonic features and how they are related in space and time. In this study we use differential travel time residuals at some strong motion accelerographic stations in the Medellin-Aburra Valley, in the northern Central Cordillera of the Colombian Andes, to discuss some aspects of the geological configuration. We based our work on the hypothesis that the differences between seismic travel time residuals among pairs of stations are a function of the differences in the surface geology and the near-surface upper crustal configuration. Our results are consistent with the volcanic rocks of the Quebradagrande Complex being less mafic, more weathered or more tectonically affected than previously thought, with the presence of a relatively thin dunite body on top of the metamorphic basement, and with a large lateral heterogeneity in the mainly mafic San Diego Stock.

三维并行高密度电法在六国化工磷石膏堆场场地勘察中的应用

工程项目实施前,确定工区地下空间分布详情是不可缺少的工作内容。三维高密度电法观测系统的布设难度大,使用常规电法仪进行采集耗时较长,在真实复杂地质条件下,应用难度大。利用并行电法采集技术,可以达到高效采集数据的目的。为准确查明某磷石膏堆场下部及周边可能形成渗漏管道的区域的三维形态,结合实际地质情况,采用并行电法进行数据采集,获取测区内真三维观测系统下的三维电法勘探数据体,然后对数据进行带地形三维反演处理和解释。结果表明:三维并行高密度电法探测场地地下空间分布具有一定的有效性和准确性。本次现场探测共圈定了5个异常区。与钻孔揭露资料吻合,为后期指导防渗帷幕施工提供准确依据.

基于瓦斯防治工程的隐伏构造勘查与瓦斯异常区域预测

隐伏构造勘查与瓦斯异常区域预测研究是瓦斯灾害防治工程的基础。根据中国煤矿生产法律规章,开采具有瓦斯灾害危险的煤层前,必须实施瓦斯抽放工程。通常,地质异常区域即是瓦斯灾害危险区,构造应力场和采动应力场的叠加会扰动煤体并加压瓦斯。为精准定位地质异常区,评价其瓦斯致灾潜能,提出了一种基于瓦斯抽采工程进行瓦斯异常区域勘测的研究方法。该方法利用抽采钻孔参数和施工记录,采集钻孔数据并计算煤层顶底板控制点坐标,进而利用二维投影图件及三维应力场模型对隐伏地质构造(如小的断层、褶曲、局部煤厚异常变化等)进行勘查和预测;通过分析小型地质构造周围的附加应力场,并对瓦斯致灾潜能进行动态预测。应用该方法,可以对地质异常区进行精细调查,揭示采煤工作面瓦斯地质演化的一般规律。其研究结果为高瓦斯或突出煤层瓦斯灾害防治措施优化设计及有效实施提供科学依据。

OCTEM法探测地下空间地质病害体的应用研究

城镇地下空间地质病害体造成地面塌陷事故时有发生,对人民群众的生命财产安全构成巨大威胁。采用地球物理方法探测和预报地下空间地质病害体是预防城镇地面塌陷事故的重要方案。瞬变电磁法(TEM)是探测地下空间地质病害体的重要方法之一。等值反磁通瞬变电磁法(OCTEM)采用免接地、小体积、弱耦合的收发一体小型天线,便于在城镇硬化地面及施工空间受限的场地进行快速探测。本文结合理论计算和实际应用来研究OCTEM对地下地质病害体的探测能力。首先基于矢量有限元实现OCTEM三维正演,研究不同地电类型地质病害体的OCTEM响应特征。根据地下地质病害体的电性特征,构建了纯低阻型、纯高阻型、低阻-高阻复合型3类地质病害体地电模型,对比分析不同地电类型的地质病害体的异常响应,并计算包含地质病害体时的响应与不包含地质病害体时的背景响应之间的相对异常。计算结果表明:OCTEM对纯低阻型和低阻-高阻复合型地质病害体比较敏感,对纯高阻型地质病害体相对不敏感。对于低阻型或低阻高阻复合型地质病害体,低阻部分与围岩电阻率差异越大、厚度越大、埋深越浅,则相对异常越大,越容易被探测。随着深度加大,OCTEM探测分辨能力将减小。最后,通过在湖南浏阳某村镇试验剖面探测地下岩溶地质病害体案例,分析OCTEM的探测效果。

巷道前方地质异常八点电源电法随掘探测响应

为可靠探查掘进巷道前方地质异常体情况,提出了八点电源随掘超前探测方法。从巷道迎头向后沿巷帮中线布置32道电极,电极间距5m。近工作面8个电极顺次做为点电源电极,采集整条测线单极-偶极装置视电阻率值。根据微分电测深探测原理,每个点电源所测得的视电阻率值可视为该点电测深结果,得到电测深曲线图和视电阻率成像图。巷道每掘进20m,将最后4个电极滚动布置到新测线前4个电极,再进行八点电源电测深数据采集,得到连续变化的电测深曲线和电测深成像结果。根据单极-偶极装置视电阻率响应公式计算了工作面超前方向地质异常球体的响应,研究结果表明:对同一地质异常球体,距离掘进工作面由远到近,电阻率响应越来越明显;低阻球体边缘到点电源距离不大于球体半径时,可以探查;高阻球体边缘到点电源距离不大于1/2球体半径时,可以探查;低阻球体的响应强于高阻球体。地质异常体半径越大,能够被探查出的超前距离越大。因此,超前0~50m范围地质异常探测精度高;超前50~100m范围地质异常探测可靠性低,适宜解释是否有较大范围的地质异常区。八点电源电法随掘超前探测能够可靠探测工作面前方地质异常的赋存情况,为工作面安全快速掘进提供地质保障。

基于重磁数据研究江苏岸外滨海断裂带及邻区构造特征

江苏岸外滨海断裂带是南黄海西部一条重要的活动断裂,孕育了多次M≥5.0的破坏性地震。该断裂带所在海域特殊的自然地理条件限制了海洋地质调查的开展,导致目前对其展布特征、断面结构、活动强度和力学性质等仍存在争议。文章基于重磁异常的定性分析和定量计算并结合前人研究成果,对滨海断裂带及邻区的构造特征进行研究,追踪了滨海断裂带可能的展布特征,并探讨了不同分段构造属性和活动性。结果表明,滨海断裂带在江苏岸外20~30 km处大致平行于岸线延伸,在废黄河口以北分叉为东、西两支。推测大致以射阳和如东海域为界,将断裂带分为3段。中段构成苏北盆地的东部边界,为长期继承性活动的深大断裂;南段为形成时代较新的平移断裂,构造活动性最强;北段的存在与否和活动性仍有待进一步调查确认。

A组煤底板灰岩地质异常体地震响应特征研究

淮南矿区A组煤的安全高效开采是保证华东地区能源供应的重要前提,准确掌握地下煤层的构造形态、发育情况是安全生产和减少事故发生的必要条件。以张集矿1613A工作面为工程背景,采用被动成像和噪声成像技术,对工作面顶底板的微地震监测资料进行分析,工作面已注浆治理的断层破碎带附近微地震事件较多,最深达到工作面下方约80 m的位置,有效验证了该断层破碎带的存在。通过反演的方法分析检波器中接收到的波形信号,获取工作面附近的波速场信息;利用西二、西三_(1)煤采区三维偏移数据体,计算了多种属性,研究了已揭示地质异常体的地震响应特征和属性特征,发现本区构造与地质异常体的研究需要特别注意蚂蚁体、最大曲率、最小曲率、局部异常、落差5个属性的指示作用。研究表明,以三维偏移数据体为基础,提取的各个属性对大断层均有显示,能够进行有效解释;对落差较小断层显示较好的属性是蚂蚁体属性和最大曲率、最小曲率、局部异常、落差属性。

Plume-lithosphere interaction in the Comei Large Igneous Province: Evidence from two types of mafic dykes in Gyangze, south Tibet, China

Two suites of mafic dykes,T1193-A and T1194-A,outcrop in Gyangze area,southeast Tibet.They are in the area of Comei LIP and have indistinguishable field occurrences with two other dykes in Gyangze,T0902 dyke with 137.7±1.3 Ma zircon age and T0907 dyke with 142±1.4 Ma zircon age reported by Wang YY et al.(2016),indicating coeval formation time.Taking all the four diabase dykes into consideration,two different types,OIB-type and weak enriched-type,can be summarized.The“OIB-type”samples,including T1193-A and T0907 dykes,show OIB-like geochemical features and have initial Sr-Nd isotopic values similar with most mafic products in Comei Large Igneous Provinces(LIP),suggesting that they represent melts directly generated from the Kerguelen mantle plume.The“weak enriched-type”samples,including T1194-A and T0902 dykes,have REEs and trace element patterns showing withinplate affinity but have obvious Nb-Ta-Ti negative anomalies.They show uniform lowerεNd(t)values(−6‒−2)and higher 87Sr/86Sr(t)values(0.706‒0.709)independent of their MgO variation,indicating one enriched mantle source.Considering their closely spatial and temporal relationship with the widespread Comei LIP magmatic products in Tethyan Himalaya,these“weak enriched-type”samples are consistent with mixing of melts from mantle plume and the above ancient Tethyan Himalaya subcontinental lithospheric mantle(SCLM)in different proportions.These weak enriched mafic rocks in Comei LIP form one special rock group and most likely suggest large scale hot mantle plume-continental lithosphere interaction.This process may lead to strong modification of the Tethyan Himalaya lithosphere in the Early Cretaceous.

瓦斯抽采地质异常区微震响应规律研究

瓦斯抽采活动会使得煤岩体应力分布发生变化,导致煤岩体内裂隙扩展发育直至破坏,出现微小量级的高频率微破裂信号。利用微震监测技术可有效识别这种微破裂信号,对抽采过程进行实时动态监测,可探查地质异常区、隐伏构造等。九龙矿15240工作面在瓦斯抽采活动影响下,在距离采线较远的某一空间区域内,单日微震事件数量成倍增长(2~12倍)且时间序列连续,该区域则识别为瓦斯抽采地质异常区。通过分析微震数据时空序列演化、垂向发育、能量等信息并总结其响应特征,结果表明:随着瓦斯抽采时间序列的延续,地质异常区微震事件活动性由强到弱,空间分布呈现“集中式-分散式”演化趋势。顶板0~5 m占比明显高于正常回采阶段,底板5~15 m占比较大。微震事件能量呈不规则U型分布,整体能量相比回采数据增长38倍,应注意加强水文地质观测。

反射槽波探测法在煤层褶曲与断层识别中的研究与应用

【背景】煤矿智能化转型中,精准识别地下异常体对地质透明化体系构建至关重要,褶曲异常体的精确探测是井下物探技术的难点,其准确辨识对减少掘进成本、回采难度及安全风险有重要意义。【目的和方法】基于以往的槽波勘探实践,发现褶曲对槽波的传播特性具有显著影响,但传统槽波反演技术难以区分褶曲与断层。为此,构建了几何形态类似、勘探距离相等的断层与褶曲数值模型,首先运用三维波场模拟技术挖掘波场信息,明确了二者波场响应差异;其次采用绕射偏移成像方法反演处理,获取了成像结果。【结果和结论】研究结果表明:(1)褶曲异常相较于断层,其反射槽波波形更为分散且模糊,不同反射点能量分布不均。(2)褶曲异常在远偏移距处的直达槽波信噪比高于断层构造,且能减缓直达槽波的衰减速度,使得直达槽波在褶曲异常中的传播距离约为断层构造中的1.5倍。(3)断层的反射槽波与直达槽波能量差异较小,而褶曲异常则表现出较大的能量差异。(4)褶曲异常的反射槽波主频低于断层构造,并导致直达槽波与反射槽波的频带变宽;褶曲异常反射槽波频率和速度均略高于直达槽波,断层构造此特征不明显。(5)断层构造的反射面通常位于断层面中上端,而褶曲异常的反射面则倾向于褶曲面中部,且褶曲异常的绕射偏移成像反射面在连续性上较断层构造差。基于上述波场特征与频散特性的深入分析,以山西阳泉某矿15号煤层为例,通过反射槽波绕射偏移成像技术,成功实现了巷道侧帮煤层中断层与褶曲的定性识别,并清晰描绘了褶曲的发育形态。研究成果不仅为采区工作面的合理布局提供了更为精确的地质依据,也为煤矿的安全生产、高效开采提供了有力的技术支撑。

基于Landsat 8和高分一号卫星数据的青海巴尔达吾地区铅、镍多金属矿化信息提取

本文主要介绍在青海巴尔达吾地区通过运用美国Landsat 8(ETM+)和高分一号数据,提取了铁染遥感异常与羟基遥感异常蚀变信息,识别地层、岩体岩性信息并总结了主要地质体遥感地质特征及解译标志,同时解译出40多条线性构造及4处环形构造。结合区内地质、物化探资料,采用地质土壤(岩石)剖面、化学样等工作手段,对圈定的8处遥感蚀变异常优选了2处进行了含矿验证,在已提取的蚀变异常内发现了品位较高的铅锌矿、镍矿,空间耦合性较高。这不仅为研究区靶区圈定、地质找矿提供了依据,同时也说明遥感技术在矿产勘查中发挥着不可或缺的作用。

无线电波反射法探测回采工作面断层技术应用

为更快捷探明井下构造情况,采用无线电波反射法对工作面断层进行探测。对无线电波传播、反射原理进行分析,通过数值模拟掌握无线电波在空巷传播以及反射能量突变规律:整体上电磁波在无障碍空巷内传播时其H_(x)分量的场强值与距离大致呈线性关系;与无断层工作面相比,存在断层的工作面接收点会在相应位置发生突变,突变幅度随着断层距离增大而减小。在数值模拟基础上,开展12407工作面无线电波反射法勘探,结果证明:无线电波反射法可以对断层构造进行辅助探查,较大落差的断层更有助于反射电磁波的形成。