In Situ U‐Th‐Pb Dating and Sr‐Nd Isotope Analysis of Bastnäsite by LA‐(MC)‐ICP‐MS

Bastnäsite is the end member of a large group of carbonate–fluoride minerals with the common formula (REE) CO₃F·CaCO₃. This group is generally widespread and, despite never occurring in large quantities, represents the major economic light rare earth element (LREE) mineral in deposits related to carbonatite and alkaline intrusions. Since bastnäsite is easily altered and commonly contains inclusions of earlier‐crystallised minerals, in situ analysis is considered the most suitable method to measure its U‐Th‐Pb and Sr‐Nd isotopic compositions. Electron probe microanalysis and laser ablation (multi‐collector) inductively coupled plasma‐mass spectrometry of forty‐six bastnäsite samples from LREE deposits in China, Pakistan, Sweden, Mongolia, USA, Malawi and Madagascar indicate that this mineral typically has high Th and LREE and moderate U and Sr contents. Analysis of an in‐house bastnäsite reference material (K‐9) demonstrated that precise and accurate U‐Th‐Pb ages could be obtained after common Pb correction. Moreover, the Th‐Pb age with its high precision is preferable to the U‐Pb age because most bastnäsites have relatively high Th rather than U contents. These results will have significant implications for understanding the genesis of endogenous ore deposits and formation processes related to metallogenic geochronology research.     

对PCM编码式GPS站点布设模式的评价和改进

本文主要对PCM编码式的布设模式进行分析和改进,介绍PCM编码式和闭锁深度倍数式2种站点布设模式,然后在最小有效距离（MED）为6.31倍断层闭锁深度的情况下,通过精度评价方法对比2种布设模式的结果,发现二者相差不大。进一步研究MED的合理选择,结果表明,MED取20倍的闭锁深度比6.31倍的闭锁深度更为合理。在MED为20倍的情况下对比研究PCM编码式和常规闭锁深度倍数式布设模式的优劣,结果表明,PCM编码式的布设模式优于常规模式。将PCM编码式的布设模式应用于川滇地区的巧家-东川剖面进行检验,发现PCM编码式的结果优于目前站点分布得到的结果,说明合理的站点布设可得到精度更优的结果。本文研究对于断层形变监测中精确获取形变参数具有重要意义。     

多测绘技术手段与遗址保护

采用全站仪离散点测量、三维激光扫描、无人机航拍对大型古遗址进行数据采集,分析了各种测绘手段的作业方法及流程,得到一系列测绘成果,并利用三维浏览软件实现遗址的三维展示,为遗址修缮与保护提供了数据支持。     

地球参考框架ITRF2014结果分析

ITRF2014是地球参考系的最新实现。该框架利用正弦函数估计负荷对台站位置的季节性效应,与ITRF2008相比,可以得到更稳定、精确的速度场;另外,ITRF2014引入了震后形变模型,可以更好地分析测站的非线性运动。本文通过分析发现:ITRF2014其原点相较于ITRF2008,其符合精度为3.5 mm;两种技术(VLBI和SLR)在2010.0历元确定的尺度因子不符值为1.18 ppb;同时,局部测量解与空间大地测量解解算的本地连接向量仍存在较大不符。     

采动区旧址文物类建筑物评价方法

针对采动区旧址文物类建(构)筑物的特殊性,文章提出采动影响下旧址文物类建(构)筑物损坏的多因素单一综合评价方法。以安源煤矿革命旧址建(构)筑物为研究对象,系统分析了革命旧址建(构)筑物的损坏原因,并确定相应的评价指标,采用加权平均法对建(构)筑物的损害进行综合评价分析。结果表明,评价结果与实际损坏程度相符,反映了革命旧址建(构)筑物不同于普通结构建筑物的特殊性,为采动区旧址文物类建(构)筑物损坏的评价方法提供新的途径。     

生态红线区管理:英国科研专用区的历史脉络与经验借鉴

作为关键生态保护区域边界线,生态红线划定当前已经上升为中国国家层面战略部署,然而当前生态红线的研究尚处于探索阶段,对于如何针对红线区域具体设计法规保障、制定管理规则、限定开发行为等方面的研究较为匮乏。鉴于英国已经较为成熟的科研专用区相关保护管理的历史经验,梳理和定位了英国科研专用区的3个发展阶段,探讨了各个发展阶段的基本原则、管理机制和实施保障的演变过程,总结英国科研专用区的规划与管理经验,提出了完善法律保障与规程规范、实施统一监管和区域统筹、并行生态补偿与保护自住、签订标准化管理协议、加强公众参与与研讨机制、提升资金保障与使用效率等对我国生态红线区管理与保障的有益借鉴。     

环嵩山地区史前时期聚落选址与水系关系研究

采用GIS空间分析方法,按照裴李岗、仰韶、龙山、夏商4个时期对环嵩山地区史前时期聚落选址与水系关系进行分析。结果表明:聚落选址与水系存在密切的关系:(1)聚落选址偏好最强的地区位于距河流水平距离为200~300 m的地区,聚落分布数量随着距离水系水平距离的增大而减少,而且聚落选址距离水系的水平距离基本不超过3 km。(2)距离水系垂直距离为20 m的范围内是聚落选址偏好程度最强的地区,聚落分布数量随着距离河流垂直距离的增加而减少,距离水系垂直距离太大,不利于古人取水,垂直距离超过40 m无聚落分布,说明聚落选址对距离水系垂直距离的偏好度在40 m以内。(3)聚落选址偏好随着水系级别的增大而降低,裴李岗时期、龙山时期、夏商时期3级水系附近聚落密度最大,而仰韶时期1级水系附近聚落密度最大。有可能因为在仰韶时期,气候属于暖湿期,相对于其他3个时期来说,降水较多,3级水系水流量可能较大,没有1级水系附近的居住环境稳定。     

青藏高原多年冻土区地温监测结果分析

Ground temperatures monitored at four observation sites in permafrost regions on the Tibetan Plateau was analyzed. It was found that the ground temperature at the depth of 12～20 m increased 0.2～0.4 K and the permafrost thickness decreased 4～5 m from the base in Xidatan Site from 1975 to 1989; and the ground temperature at the depth of 6～15 m increased 0.2～0.4 K in Kunlun Pass Site from 1982 to 1997. Contrast observations show that a sand cover, 15～20 cm in depth, can result in a ground temperature decrease of 0.1～ 0.2 K in MS66 Site; and a removal of vegetation can result in a ground temperature decrease of some 0.2 K in Hoh Xil Site. The monitor demonstrates that many factors that control permafrost developing have duality, e.g., sand and vegetation are able to increase or decrease the ground temperature. These factors, in conjunction with permafrost behaviour, play different roles under different conditions. Therefore, it is necessary to study, understand and evaluate permafrost and its engineering geological properties taking the viewpoint of dynamic variation.     

Preliminary Study on Horizontal Deformation and Tectonic Activity in the Northern Part of North China Using GPS Remeasurement Results

In this paper, the baseline variation and displacement vector was analyzed using the calculated results of GPS measurements carried out from 1995 to 1996 in North China. Based on these analytical results, we studied the recent tectonic activity. In general, the regional extension is dominant in the direction of proximately EW, but there is a difference in the SN direction. Extension is significant in the Shanxi fault-depression zone and Bohai region, while compression with strike-slip is characterized along the Yishui-Tancheng segment of the Tanlu fault zone. The baseline shortening zone is distributed along the Baotou-Zhangjiakou-Ninghe areas. It is a boundary zone of regional variation where many differences of crustal horizontal deformation are discovered between the southern part and the northern part of this zone. The baseline shortening zone in NE direction is distributed along the Jianchang-Tangshan-Gucheng area. It is consistent with the Tangshan-Xingtai seismic zone which indicates that tectoni     

Site amplification in the Lijiang Valley, Yunnan Province

The site amplifications for three stations, Libin (LIBI), Baisha (BASH) and Yulong (YULG) situated respectively in the southern, middle and northern parts of Lijiang Valley, are obtained by analyzing the S-wave soil/bedrock and microtremor horizontal/vertical spectral ratios. The data are digital recordings for the aftershocks of the Lijiang MS=7.0 earthquake on February 3, 1996. In the frequency range of 1～4 Hz, the S-wave soil/bedrock spectral ratio of E-W component for LIBI is the largest and amounts to 4.5. The microtremor soil N-S/vertical (V) spectral ratio is approximate to 1, E-W/V is about 4.5 and the same with above soil/bedrock spectral ratio. It is shown that the vertical and N-S components of microtremor have not been amplified by the soil and the spectral ratios for BASH and YULG are further evaluated. They have similar characteristics with that of LIBI. In above frequency range, both N-S/V ratios are approximate to 1, while the E-W/V ratio is about 6 for BASH, 4.5 for YULG. Lijiang Valley is characterized by the trans-valley directional site response.