Sulfur Content and Isotopic Ratio of Cambro-Ordovician Carbonate Rocks from South Korea: A Possible Source for Mesozoic Magmatic-hydrothermal Ore Sulfur

Abstract: Carbonate rocks of Cambrian (18 samples) and lower-middle Ordovician (11 samples) ages from South Korea were analyzed for sulfur contents of structurally substituted sulfate (SSS) and sulfides and their δ³⁴S values. The δ³⁴S values of SSS ranging from +25.9 to +45.2 permil, are averaged as +33.6 and +33.5 permil for the Cambrian and Ordovician rocks, respectively, which indicate high δ³⁴S values of the Cambro-Ordovician seawater. The SSS contents in the carbonate rocks are low being 2.9 to 17.3 ppm S (averaged as 7.0 ppm S). Sulfide sulfur, on the contrary, is much abundant containing 3 to 1,880 ppm S and the δ³⁴S values range widely between –17.6 and +31.1 permil. Sulfide sulfur of the studied rocks excluding impure carbonates has an average content of 187 ppm S and δ³⁴S value of +12.8 permil (n=24). The estimated δ³⁴S (sulfate–sulfide) values, which range from 13.8 to 25.4 permil in general with a few exceptions from 36.5 up to 52.3 permil for some impure carbonates, may provide evidence for the persistent oceanic anoxia with its temporary recovery during the Cambro-Ordovician time.
The SSS and sulfide sulfurs have often higher δ³⁴S values than the Mesozoic-Cenozoic ore sulfur (Ishihara et al., 2000). Since carbonate rocks are very reactive with circulating hydrothermal ore solution, high δ³⁴S values of the Korean ore deposits might be caused to some extent by ³⁴S enrichment from the host carbonates, resulting in the low SSS contents observed.     

Study on Paleoenvironment since Late Glacial Eooch in Lanzhou Area, China

The Hongzuisi Section in Lanzhou area is used to infer the paleoclimate since the late glacial epoch. Through combined analysis of organic carbon isotope and CaCO3 content, paleoenvironment evolution of Hongzuisi Section since the late glacial epoch is discussed. There were changes in both drymoist and warm-cold. Especially the climate changes can be compared with synchronous sections of other areas, which provides useful information for our future forecast.     

云南水汞在姚安6.5级地震前的异常特征分析

对2000年1月15日姚安6．5级地震前后云南水汞异常进行分析研究，结果表明：在9个观测台站中，地震前有1个观测台站的水汞出现中期趋势异常，1个台站的水汞出现远震异常，4个台站的水汞出现短期异常，1个台站的水汞出现临震异常。地震前3个月内，水汞短期异常有活跃，平静的过程，在平静中(仅1个台站出现临震异常)发生姚安6．5级地震。姚安地震发生在距出现远震异常的水汞观测台站70km的地方。出现远震异常的水汞观测台站附近，可能是未来强震的发震地区。     

Simultaneous radio and optical observations of the mid-latitude atmospheric response to a major geomagnetic storm of 6–8 April 2000

Basic properties of the mid-latitude traveling ionospheric disturbances (TIDs) during the maximum phase of a major magnetic storm of 6–8 April 2000 are shown. Total electron content (TEC) variations were studied by using data from GPS receivers located in Russia and Central Asia. The nightglow response to this storm at mesopause and termospheric altitudes was also measured by optical instruments FENIX located at the observatory of the Institute of Solar-Terrestrial Physics (51.9°N,103.0°E), and MORTI located at the observatory of the Institute of Ionosphere (43.2°N, 77.0°E). Observations of the O (557.7 and 630.0 nm) emissions originating from atmospheric layers centered at altitudes of 90 and 250 km were carried out at Irkutsk and of the O₂(b¹∑_g⁺−X³∑_g⁻) (0-1) emission originating from an atmospheric layer centered at altitude of 94 km was carried out at Almaty. Our radio and optical measurement network observed a storm-induced solitary large-scale wave with duration of 1 h and a wave front width of no less than 5000 km, while it traveled equatorward with a velocity of 200 m/s from 62°N to 38°N geographic latitude. The TEC disturbance, basically displaying an electron content depression in the maximum of the F2 region, reveals a good correlation with growing nightglow emission, the temporal shift between the TEC and emission variation maxima being different for different altitudes. A comparison of the auroral oval parameters with dynamic spectra of TEC variations and optical 630 nm emissions in the frequency range 0.4–4 mHz (250–2500 s periods) showed that as the auroral oval expands into mid-latitudes, also does the region with a developed medium-sale and small-scale TEC structure.     

野外简易脱气装置简介

根据水力学原理结合水氡在实验室分析中水样鼓泡脱气的方法 ,进行了大量的野外试验 ,研制开发了野外简易脱气装置。通过几个月的试观测 ,脱气装置气流稳定 ,脱气效率高 ,完全可以满足自动化观测仪器对气量的需求。该装置解决了地下水化学在野外冷水泉无法进行气体观测的难题 ,而且制作简单、费用低廉 ,非常便于推广。     

乌鲁木齐10号泉He含量变化的映震特征

本文从监测泉点的水文地质概况入手，结合近19年来的资料分析了10号泉水中氦含量变化的映震特征：氦含量变化的地震前兆异常基本上都是正异常，且具有较好的重复性，泉点即流量测值遵循：背景值一趋势性上升（或突升）－最高值－趋势性下降（或突降）－恢复至背景值的变化过程。而地震常常发生在氦含量由高变低的过程中。最后初步认定了泉点较好的地质构造环境和氦特有的化学特性是该泉氦具有映震灵敏性的原因。     

数字城市建设研究

数字城市建设是一项复杂的系统工程，需要做好规划，解决管理、制度、标准以及必须的关键技术等问题。文章在分析了数字城市建设目标和内容的基础上，探讨了数字城市建设的基本原则，提出了数字城市建设的具体实施方案。     

Sensitivity Analysis of a Feedforward Neural Network for Considering Genetic Mechanisms of Kuroko Deposits

Exploration for volcanogenic massive sulfide deposits of the kuroko-type is underway in many places. Clarifying the spatial patterns of the metals in kuroko deposits will be useful for understanding their genetic mechanisms and for future exploration of such types of deposits. This study represents a spatial distribution analysis on the contents of principal metals of kuroko deposits: Cu, Pb, and Zn, in the Hokuroku district, northern Japan, by a feedforward neural network and 1917 sample data at 143 drillhole sites. The network, which consists of three layers, was trained by the principle of SLANS in which the numbers of neurons in the middle layer and training data are changed to improve estimation accuracy. Using the weight coefficients connecting adjacent neurons, sensitivity analysis of the neural network was carried out to identify factors influencing spatial distributions of the three metals. The coordinates depth (z) direction, Bouguer gravity, and specific lithology such as dacite were determined to be influencing factors. The high frequency of the z coordinate signifies that the metal contents differ to a large extent by depth. The sensitivity vector was defined using sensitivity coefficients for x, y, and z coordinates of an estimation point. We determined that the directions of large vectors were different inside and outside of the Hanawa-Ohdate area. This characteristic is considered to originate from the differences in the permeability of fractures that became the paths for rising ore solutions, and the depths that the solutions mixed with sea water.     

Isotopic Tracing of Trophication Processes over the Last Millennia on Lake Chenghai

Multi-parameter studies (stable isotopes in carbonate and organic matter, pigment,organic carbon and nitrogen contents) from a 660-yr continuous sediment core from Lake Cheng-hai, a closed, eutropic lake in southern China, provide information on lake historical eutrophi-cation. During the last 660 years, great changes have taken place in productivity and eutrophi-cation of Lake Chenghai in response to human activities. In 1690, the productivity of the lakebegan to increase as Lake Chenghai became closed from agriculture in the lake‘‘ s watershed. In 1942, Lake Chenghai evolved to eutrophic state, marked by an increase in organic carbon, ni-trogen, CaC03, pigment contents and obvious negative values of stable isotopes, which is more or less simultaneous with the large-scale population immigration during the period. In 1984, in-tensive human activities induced modern lacustrine productivity and eutrophic level. Human-in-duced trophic changes during the past few decades have affected the Lake Chenghai ecosystem tosuch an extent that it has never experienced before in the last 660 years.     

利用核磁共振方法研究水文地质问题及应用实例

地面核磁共振找水方法是目前唯一直接找水的物探新方法。本文在介绍NMR方法原理的基础上,结合NMR方法技术特点和在中国的应用实例,论述了NMR方法在探测地下水、地下水资源评价等方面的效果,并提出了进一步开展新方法的工作建议。