吕梁地区临县东部汉高山群构造演化特征浅析

吕梁地区汉高山群作为华北克拉通内第一套沉积盖层,其构造演化历程的研究对华北克拉通内中元古代裂谷盆地的形成与演化具有重要指导意义。本文选择吕梁地区临县东部汉高山地区的一条剖面,通过2D-Move模拟软件对该区内汉高山群及其同沉积的方山断裂进行反演与正演模拟。结果显示：该区在中元古代早期为一断陷盆地,随吕梁隆起的抬升,中寒武统海相沉积以角度不整合覆盖于汉高山群之上,在经历中生代构造反转后,方山断裂反向活化为逆断层,吕梁汉高山地区转变为挤压环境下的陆内造山带,汉高山群逐渐被抬升至地表后继而被剥蚀形成现今构造格局,表现了华北克拉通中部吕梁地区多期改造的特点。

     

三峡库区黄陵背斜形成机理及与滑坡群关系

黄陵背斜、秭归向斜是三峡地区构造地质研究热点之一,前人将其划归于秦岭造山带的组成部分,认为是东西向构造后期改造的结果;分布于此区的仙女山断裂是否穿越长江也是争论的焦点问题之一.这些问题的解决对澄清研究区地质灾害分布特征具有重要意义.笔者在前人研究的基础上,从沉积学、构造地质学角度,在大量野外地质研究工作的基础上,提出了新的看法:黄陵背斜、秭归向斜、当阳向斜、仙女山断裂同属统一的构造体系,其形成和演化与中国东西部构造格局的变迁一致,黄陵背斜具有断层相关褶皱的特点,秭归向斜具有前陆挠曲型盆地构造属性;仙女山断裂形成之初具有传递断层的属性,后期又经历了引张、挤压演化过程,不存在跨越长江向北延伸的问题;受秭归向斜沉降幅度以及东西向构造与南北向构造复合影响,在研究区形成3个滑坡聚集区,分别为贾家店滑坡聚集区、八字门向家店滑坡聚集区、兴山县城附近滑坡聚集区.     

地气测量的原理及其在地质勘查中的应用

本文介绍了金属气体和金属微粒的形成、地气流的垂向搬运以及内生金属矿床周围地气分散晕的广泛存在,同时还介绍了地气测量在找隐伏矿和勘查运积物覆盖下的岩石类型的应用前景。     

Contribution des réseaux de neurones artificiels (RNA) à la caractérisation des pollutions de sol. Exemples des pollutions en hydrocarbures aromatiques polycycliques (HAP)Artificial Neural Networks (ANNs) characterisation of soil pollution: the Polycyclic Aromatic Hydrocarbons (PAHs) case study

We develop the ANNs (Artificial Neural Networks) method to explore contaminant concentration profiles observed in soils of polluted sites. ANNs are particularly efficient in simultaneous analysis of numerous parameters and in identification of complex relations involving field data. Applying the ANN models on a PAH (Polycyclic Aromatic Hydrocarbon) database, we extracted the most characteristic components of known contaminations and applied it to identify the source type of similar polluted sites. The performed tests prove the generalisation capability of the selected ANN model. To cite this article: A. Dan et al., C. R. Geoscience 334 (2002) 957–965.     

A comparison of three gravity inversion methods for crustal thickness modelling in Tibet plateau

Crustal thickness can be determined by gravimetric methods based on different assumptions, e.g. by isostatic hypotheses. Here we compare three gravimetric inversion methods to estimate the Moho depth. Two Moho models based on the Vening Meinesz-Moritz hypothesis and one by using Parker-Oldenburg’s algorithm, which are investigated in Tibet plateau. The results are compared with CRUST2.0, and it will be presented that the estimated Moho depths from the Vening Meinesz-Moritz model will be better than the Parker-Oldenburg’s algorithm.     

地幔过渡带和下地幔组成与深部热源研究进展

受时空不可及性的制约,地质学家在探究地球深部物质组成方面仍显得很被动,尤其是在探究地幔物质组成方面显得更加艰难.目前,科学家们探测地幔物质主要依靠地球物理学和实验矿物学、岩石学方法相结合的手段来进行.结果表明,地幔过渡带主要的矿物组成有瓦士利石、林伍德石、超硅石榴子石以及少量的CaSiO3.下地幔主要矿物组成有钙钛矿(Pv)、后钙钛矿(PPv)和镁方铁矿(Mw).在讨论过渡带和下地幔物质组成的基础上,归纳总结了地球内部热源的三种来源,分别是放射性元素的衰变热和初始熔融硅酸盐地球长期冷却放出的热、核幔边界在地磁场和高电导率物质的作用下产生的热以及来自地核的热.这些结论对研究地球深部动力学和热力学过程有重要意义.     

北天山乌鲁木齐河流域面积-高程积分及其地貌意义

定量构造地貌研究有助于理解构造与地表过程之间的耦合关系及其对地形地貌发育的影响,数字高程模型(DEM)和地理信息系统(GIS)空间分析技术的结合为开展这方面的研究提供了新途径.利用这一方法,对北天山乌鲁木齐河流域进行地貌计量指标的综合分析.构造上,乌鲁木齐河流域分为山前坳陷区、南山隆起带、后峡断陷带以及天山主脉等构造分区.本文首先分析了DEM数据精度、流域面积与空间分布特征对面积-高程积分的潜在影响,根据分析结果,选择合适的面积阈值对乌鲁木齐河流域开展面积-高程积分分析,进一步结合高程频率分布特征探讨该流域地形地貌演化特征.结果表明,1)面积-高程积分受DEM数据精度的影响不显著,但其具有明显的流域面积和空间依赖性;2)基于面积-高程积分分析,乌鲁木齐河流域各构造分区的地貌演化阶段存在差异,除后峡断陷带地貌演化趋于老年阶段外,其余均处于壮年演化阶段;3)各构造分区平均高程频率分布状态表明,山前坳陷区、南山隆起带和天山主脉地形目前均处于前均衡—均衡状态演化阶段,后峡断陷带地形则为后均衡演化阶段.     

新疆乌鲁木齐地区积雪深度演变规律及对气候变化的响应

积雪深度D是水文模型和气象预测中的重要参数之一.基于新疆乌鲁木齐站1961-2013年积雪深度D及气象资料,分析了积雪起止日期、持续期特征和D的时间变化规律,并对比了不同模型对于D过程变化的适配效果.此外,对最大积雪深度Dmax进行了趋势检验,并简要分析了气象要素对D和Dmax的影响.结果表明:乌鲁木齐积雪的持续期在73~207 d范围变化,平均持续141 d,积雪开始日期和终止日均呈推迟趋势,积雪持续期呈增加趋势,但其趋势均不显著.可将积雪年内的D变化类型分为多峰缓变型、右偏型、尖峰型以及平峰型4种,分别用不同模型适配后发现整体上模拟效果较好的是Gaussian函数.在1961-2013年53 a期间的Dmax不具有自相似结构,但有显著上升趋势.气温尤其是最低气温与的D相关性最好,冷季降水总量与Dmax有的正相关关系,表明气温和同时期降水与积雪变化关系密切.春季迅速升温过程及一定的累积积雪深度可能令融雪型洪水爆发,其对应的年型为尖峰型和平峰型.     

Locating the Melody of the Drives

Psychoanalysis has profoundly influenced those social theories that inform qualitative methodology in human geography. Yet many geographers are skeptical about the value and viability of psychoanalytic methodology because of its alleged reductionist causal explanations and relativistic interpretations of data. Drawing on the work of Slavoj ?i?ek, which affirms Jacques Lacan's undermining of the dualism of causality versus sense, this article illustrates the potential value of Lacanian psychoanalysis as a qualitative methodology in geography. Using a methodological case study from my research on Jamaican tourism, I illustrate how we can locate a Lacanian understanding of the drives in the interactions between tourists and hotel workers. In so doing, the article provides new insights into the enduring allures of tourism's commodity-form by focusing on how the object petit a—a chimerical object that incites desire and an unattainable object that the drives encircle—takes place in customer service and entertainment activities.     

The evolving agricultural landscape of post-plantation Hawai‘i

Hawai‘i's agricultural landscape was previously dominated by large monocrop plantations of sugar cane and pineapple, but following a sweeping series of plantation closures beginning at the end of the twentieth century, that era has concluded. The last spatial assessment of Hawai‘i's agricultural footprint was completed in 1980, during the active plantation period. Here we present the results of a 2015 statewide assessment of the commercial crop footprint for Hawai‘i, based on World-View 2 satellite imagery and supporting datasets. We analyzed changes relative to the 1980 baseline on both a statewide and regional basis, to better understand how Hawai‘i's agricultural system has evolved in the post-plantation era. Sugar cane and pineapple saw dramatic reductions during this period, collectively losing more acres (257,000) than were planted for all crops combined (152,000) in 2015. Idle plantation lands and past plantation-era investments in irrigation and other infrastructure have created opportunities for other types of agriculture, despite rising land values, new and existing tropical diseases, and other challenges. Seed crops, primarily for genetically modified corn trials, were the second largest crop in 2015 (24,000 acres) despite having no mapped footprint in 1980. Commercial forestry, also absent in 1980, covered 23,000 acres in 2015. Macadamia nut, coffee, and diversified agriculture also all saw significant gains in their footprints, with coffee plantings increasing >250% during this period. Despite these gains, the Hawaiian Islands continue to have an extremely low degree of self-reliance for food production. The Oahu plain, adjacent to the major population center of Honolulu, has the most potential for considerably increasing the production of local produce, but without changes in consumption patterns and significant efforts to protect agricultural land from development, any increases in local food production will continue to be incremental. The post-plantation agricultural landscape in Hawaii is smaller, more diversified, and more nimble than it was in 1980, reflecting inter-island geographic differences in land use, history, and ownership. Mapping and assessing spatial changes in agricultural activity over time can provide valuable insights for decision-makers and communities as they continue to define what agriculture should look like in the post-plantation era. Our results suggest that Hawai‘i's agricultural landscape and overall production capability will continue to contract without substantial changes in policy and practice.