地震预报思路的再讨论

文中回顾了1974年提出的“块、带、源、兆、触、报”六字预报思路，并基于近20年来的研究对此进行了补充和深化。     

新疆且末县吐孜敦古地震形变带及其年代问题

新疆且末县拟在吐拉乡阿尔金活动断裂带上修建水库。水库近场区内沿阿尔金活动断裂存在一条古地震破裂形变带。为了对水库进行安全性评价 ,采用地貌风化剥蚀法确定了古地震形变带的形成年代。该次古地震事件的发生时间大约距今 4 0 0年前     

南北地震带强震复发间隔的估计

通过对南北地震带各主要断裂带历史强震的时空特点研究 ,试图寻找出带内各主要构造带强震的复发和填充特征 ,并在此基础上研究其差异性 ,对未来各带发生强震的危险性作出估计     

天山西部中山带积雪变化趋势与气温和降水的关系——以巩乃斯河谷为例

根据位于巩乃斯河谷的天山积雪雪崩研究站近30年来的年最大雪深、月平均气温、月降水量观测记录，用平均差值法、最小二乘法、自回归滑动平均法检验了天山西部中山带积雪、冷季降水、冷季平均气温的变化趋势，结果表明，天山西部中山带积雪呈增加趋势，近30年来年平均增加1.43%，与青藏高原、南极大陆及格陵兰冰盖表面积雪积累增加相一致。天山西部中山带冷季气温和降水的变化趋势也是增加的，其中冷季降水平年平均增加0．12％，而冷季气温升高了0．8℃，积雪与冷季气温之间存在着弱的负相关关系，而与冷季降水呈显著的正相关关系。积雪的增加主要是因为气候变暖引起的冷季降水的增加对积雪增加的贡献大于由于冷季气温升高而造成积雪减少的贡献的结果。     

Use of Noise to Augment Training Data: A Neural Network Method of Mineral–Potential Mapping in Regions of Limited Known Deposit Examples

One of the main factors that affects the performance of MLP neural networks trained using the backpropagation algorithm in mineral-potential mapping isthe paucity of deposit relative to barren training patterns. To overcome this problem, random noise is added to the original training patterns in order to create additional synthetic deposit training data. Experiments on the effect of the number of deposits available for training in the Kalgoorlie Terrane orogenic gold province show that both the classification performance of a trained network and the quality of the resultant prospectivity map increasesignificantly with increased numbers of deposit patterns. Experiments are conducted to determine the optimum amount of noise using both uniform and normally distributed random noise. Through the addition of noise to the original deposit training data, the number of deposit training patterns is increased from approximately 50 to 1000. The percentage of correct classifications significantly improves for the independent test set as well as for deposit patterns in the test set. For example, using ±40% uniform random noise, the test-set classification performance increases from 67.9% and 68.0% to 72.8% and 77.1% (for test-set overall and test-set deposit patterns, respectively). Indices for the quality of the resultant prospectivity map, (i.e. D/A, D × (D/A), where D is the percentage of deposits and A is the percentage of the total area for the highest prospectivity map-class, and area under an ROC curve) also increase from 8.2, 105, 0.79 to 17.9, 226, 0.87, respectively. Increasing the size of the training-stop data set results in a further increase in classification performance to 73.5%, 77.4%, 14.7, 296, 0.87 for test-set overall and test-set deposit patterns, D/A, D × (D/A), and area under the ROC curve, respectively.     

Use of Fuzzy Membership Input Layers to Combine Subjective Geological Knowledge and Empirical Data in a Neural Network Method for Mineral-Potential Mapping

Use of GIS layers, in which the cell values represent fuzzy membership variables, is an effective method of combining subjective geological knowledge with empirical data in a neural network approach to mineral-prospectivity mapping. In this study, multilayer perceptron (MLP), neural networks are used to combine up to 17 regional exploration variables to predict the potential for orogenic gold deposits in the form of prospectivity maps in the Archean Kalgoorlie Terrane of Western Australia. Two types of fuzzy membership layers are used. In the first type of layer, the statistical relationships between known gold deposits and variables in the GIS thematic layer are used to determine fuzzy membership values. For example, GIS layers depicting solid geology and rock-type combinations of categorical data at the nearest lithological boundary for each cell are converted to fuzzy membership layers representing favorable lithologies and favorable lithological boundaries, respectively. This type of fuzzy-membership input is a useful alternative to the 1-of-N coding used for categorical inputs, particularly if there are a large number of classes. Rheological contrast at lithological boundaries is modeled using a second type of fuzzy membership layer, in which the assignment of fuzzy membership value, although based on geological field data, is subjective. The methods used here could be applied to a large range of subjective data (e.g., favorability of tectonic environment, host stratigraphy, or reactivation along major faults) currently used in regional exploration programs, but which normally would not be included as inputs in an empirical neural network approach.     

火山活动与金矿床

火山活动不仅对铁、铜多金属矿床的形成具有重要意义，而且对金矿形成也是至关重要的。笔者多年在火山岩分布区的工作的整理大量国内外大型超大型矿床矿田地质资料，深切地认识到火山作用在金矿形成过程中的重要意义。本文将从金矿床地质成因类型划分及其规模和资源量、各类型矿床的地质条件分析来说明这一认识，并初步总结了找矿工作中应注意的问题和标志，试图来推动火山岩地区金矿找矿工作。由于陆相火山岩金矿较为直观，因此本文着墨较少，而着重说明海底火山活动与金矿形成的内在联系。     

西藏斑岩铜矿的前景展望

世界斑岩铜矿主要产于中生代一新生代环太平洋带、古特提斯带和古生代中亚—蒙古带，因为上述3带为聚合板块集中分布地区。中国西藏集中了金沙江聚合带、雅鲁藏布江聚合带和怒江—班公错聚合带，为世界上聚合板块最发育地区之一，具有较长的大洋板块俯冲和陆—陆碰撞的造山历史，构造—花岗质岩浆十分发育，其中深源高侵位的花岗质斑岩分布广泛，对于形成斑岩铜矿和其他相关矿床十分有利，为找矿评价斑岩铜(金)矿很有前景的地区。笔者借鉴世界和中国评价斑岩铜矿的经验，同时收集了西藏近年来找寻评价斑岩铜矿有关的地质资料，对西藏斑岩铜矿的前景进行了展望。     

郯庐断裂带的平移运动与成因

在华北、华南板块碰撞期间，郯庐断裂带究竟是何种边界仍是没有解决的重大地学问题，许多学者对此提出了不同的构造解释模式。关于郯庐断裂的平移距离仍存在着较大的分歧与有待深入研究之处。在华北、华南板块拼合之后，郯庐断裂带发生了一次大规模的左行平移，其糜棱岩的^40Ar／^39Ar年龄为132～119Ma，指示为早白垩世的平移活动，平移活动中伴生了强烈的岩浆活动。这期左行平移标志着中国东部构造的重大转折，是滨太平洋构造对前期古特提斯构造的叠加，其动力学机制为太平洋区伊侨奈岐板块突然出现的高速斜向俯冲。     

青藏高原北部可可西里狮头山含硬玉岩类的基本特征及地质意义

描述了可可西里山南狮头山含硬玉岩类的岩石学、矿物学特征。含硬玉岩类的原岩为辉长岩，围岩为石炭—二叠系。由于变质作用不彻底，保留有原岩的矿物组合。典型的高压变质矿物组合为：钠长石 硬玉 霓石 蓝闪石 绿帘石 绿泥石。硬玉SiO2、FeO偏低，Al2O3、Na2O明显偏高，变质矿物组合中以富钠矿物为主，缺少石英，与国内外含硬玉岩类的原岩成分、变质矿物组合均不相同，是一种新的高压低温硬玉岩类。狮头山高压变质带向西延至若拉岗日、大横山一带，与北侧的西金乌兰—金沙江板块缝合带(西段)平行产出，以此推测缝合带南侧的羌北—昌都板块向北消减于巴颜喀拉板块之下。