寒冻条件上热力作用对岩石破坏的模拟实验及其分析

选取青藏高原不同地区、不同类型的岩石经过预加工处理后,使之处于低温条件下具有较强热辐射变化的环境中,以调查寒冷条件中的岩石在强烈热辐射作用下的表现。实验表明,寒冷条件下较强的热源辐射可以产生快速的环境温度变化,并导致相应的岩石内部温度变化,这种变化幅度可以使矿物产生强烈的缩并导致岩石内部结构的破坏。岩石的组构决定着其风化的进程,这表现在不同类型的岩石在水饱和与盐饱和的条件下,实验后的超声波传输速率与重量变化有一定差异。     

柴达木盆地北部新生代构造运动及其对盐湖演化的影响

新生代以来,印度板块与青藏高原发生了强烈的碰撞,由此而产生的远程效应导致柴达木盆地北缘的阿尔金山脉晚古近纪以后发生了强烈的走滑,并导致盆内构造形式发生了一系列变化。在前人对盆地构造运动、古地磁、古地理及岩石地球化学研究结果的基础上,提出了上新世以来在NE和近NS向共同挤压作用的影响下,盆地内部棋盘格式不均匀隆升控制了柴达木盆地北部湖盆的形成,对后期盐湖沉积产生了重要影响。     

新疆和田河流域柽柳沙堆的生物地貌发育过程

柽柳沙堆是我国干旱区分布最为广泛的灌丛沙堆类型之一。在实地考察新疆和田河流 域柽柳生态地理特征、测量223 个柽柳沙堆形态, 并在两个野外观测点上实测4 个沙堆的风沙流剖面, 结合室内风洞实验段风速8 m/s 条件下模拟沙堆风流场结构等综合分析方法, 本文探讨了柽柳沙堆的生物地貌学特征及其发育过程。结果表明: 研究区柽柳的生态类型属于以胡杨林与灌木林下土壤为基础的吐加依土生境类型, 这个生境类型可以进一步划分为三个亚生境, 这些亚生境反映了柽柳沙堆不同发育阶段的生态环境特征。由于柽柳灌丛的寿命长、木质化枝干的刚性较强、根株萌发力强耐风蚀沙埋, 可对地面风沙流运行产生强烈扰动, 其风速剖面有别于芦苇沙堆和骆驼刺沙堆, 风流场结构有利于聚集风沙, 因此风沙依托柽柳灌丛堆积发育而成的柽柳沙堆平均坡度较大、沙堆存活与发育的周期也较长     

从香港地质谈到中国农业生态

在热带条件下，不同种类岩石受到强烈的化学风化作用，并导致某些环境问题，香港在这方面提供了十分典型的例子。在香港，岩石风化厚度可达８０ｍｉｎ，普通成岩矿物长石和云母被转化为粘土矿物埃洛石和高岭石，风化岩密度一般降低４０％￣８０％，埃洛石密度看来是亚稳定的，随年龄的增加而降低。在老于晚侏罗纪或早白垩纪的岩石中，还未临别出埃洛石。埃洛石、高岭石及其风化产物少含植物所需营养元素，且阳离子交换能力低，因而所     

简述岩石室内试验方法及物理力学指标的关系

岩石的物理性质包括:饱和吸水率、饱和密度、自然吸水率、颗粒密度以及干密度等。通过试验研究某实际水利输水工程的代表性岩样的物理力学性质,得到岩石的物理参数和岩石在饱和水状态下及干燥状态下的泊松比、单轴抗压强度、内摩擦角及弹性模量等力学性质参数。本文通过对试验结果及数据的整理分析,并对岩石不同力学性质参数以及物理性质参数之间的关系进行探讨,明确岩石力学性质参数和物理性质参数之间的关系,旨在为日后相似工程提供数据参考。     

广州岩溶地区岩石地基承载力分析

岩溶地质条件下岩石地基的受力性状比普通地质条件下要复杂得多,岩石地基的承载力与桩身周围溶洞的大小、分布、溶洞个数、桩端持力层情况等因素有着密切关系。本文结合工程实例,将根据岩基荷载实验法、岩石室内饱和单轴抗压强度计算法分析地基承载力。     

不同沙源供给条件下砾石床面的风沙流结构与蚀积量变化风洞实验研究

通过对不同沙源供给条件下各种砾石床面的风沙流结构、床面风蚀及堆积沙量变化的风洞实验,结果表明,风沙流结构是判断戈壁风沙流饱和与不饱和的一个重要途径,不同的戈壁风沙流结构对床面输、阻沙特性具有不同的指示意义。近地表0～6 cm高度内的风沙流结构决定了床面的输、阻性质,而6 cm以上的风沙流结构反映了风力对沙物质的输送状况。沙源供给的丰富与否,决定了风沙流的饱和程度,以及风沙流在砾石床面产生的蚀积状况。同等风速条件下,饱和风沙流的输沙率是非饱和风沙流输沙率的2～8倍。在饱和风沙流情形下,床面过程总体以积沙为主,且随风力的增强,床面积沙量急剧增加。在不饱和风沙流情形下,砾石床面总体以风蚀和输送沙物质过程为主,风沙流结构在0～2 cm高度内反映出砾石床面具有明显的阻沙功能,在2～5 cm高度上出现最大输沙值。     

干旱荒漠区土地利用方式快速转变对土壤入渗性能的影响

研究不同土地利用类型下土壤入渗及其影响因素,有助于城市土地利用管理及径流调节。以快速城市化的兰州新区6种土地利用类型为例,利用圆盘入渗仪,对土壤水分入渗过程进行了实地测量,并利用主成分分析对影响因素进行研究。结果表明：城市化过程中土地利用变化使土壤砂粒和容重增加,总孔隙度和饱和含水量降低;待建地和人工林地的土壤入渗参数值均低于其他土地利用类型。土壤入渗率与有机质含量、总孔隙度、饱和含水量、粉粒含量正相关,与容重和砂粒、黏粒含量负相关。城市化过程中土地利用类型向待建地的转变改变了土壤理化性质及土壤水分入渗能力。     

城市地域地表温度-植被覆盖定量关系分析--以深圳市为例

地表温度-植被覆盖间的关系一直是城市热岛研究的热点之一,两者均为描述生态系统特征的重要参数。本文利用深圳市2004年的ETM+影像,基于遥感技术提取相关的下垫面类型、地表温度和植被覆盖等信息,探讨不同下垫面类型对地表温度-植被覆盖关系的影响,并结合分形维度计算方法,比较不同分辨率下地表温度、植被覆盖及其相关关系的变化。研究结果表明,植被覆盖程度与地表温度之间存在明显的负相关,并且在不同的植被覆盖程度下,地表温度-植被覆盖关系呈现分段线性关系。下垫面类型及其组合主要通过植被覆盖的分布对地表温度产生影响。而在不同空间分辨率下(30m至960m),地表温度和植被覆盖的空间变异程度均表现为先升后降,在120m的分辨率下,两者的相关程度达到最高。结果证实区域植被覆盖状况可直接影响辐射、热动力以及土壤水分等多种地表特征,从而导致地表温度分异等。     

龙马溪组页岩静态弹性特征分析

在页岩气储层的勘探开发过程中,页岩的岩石力学特征以及破坏机理可以为油气井的钻探设计、储层改造措施、方案设计和井壁稳定性评价提供一定的技术支持。基于此对龙马溪组页岩样品进行了岩石静态弹性力学实验,并利用扫描电镜对破坏后样品的断面进行了观测,发现不同样品的应力应变关系主要为弹性变形和弹—塑性变形,破裂特征主要为劈裂式破裂和单剪切破裂,并且在高围压加载条件下,样品由脆性逐渐转化为塑性,同时不同泥质含量的样品具有不同的裂隙发育特征。     

Newtontoppen granitoid rocks, their geology, chemistry and Rb-Sr age

A post-tectonic Caledonian granite in southern Ny Friesland has been fully mapped and the following new names are proposed: the Chydeniusbreen granitoid suite, consisting of the Raudberget granitoid body in the north; the Newtontoppen granitoid body in the middle; and the Ekkoknausane granitoid body in the south
The contact relationships, internal structures and distribution of various rock types infer an asymmetric lopolith or a harpolith-like body, a large sickle-shaped intrusion stretched in the direction of general tectonic transport, for the Newtontoppen granitoid body.
Seven rock types are described in the Newtontoppen granitoid and four emplacement stages are recognised. The major rock types seem to have an alkali-calcic to alkalic bulk rock chemistry and show a transition between I- and S-type granite derived from anatectic melting of various protoliths under relatively high temperature conditions. Possible later K₂0 introduction modified the earlier formed rock types.
A Rb-Sr whole rock age of 432 ± 10 Ma has been obtained by a seven point isochron with MSDW = 2.59 and an initial Sr isotope ratio = 0.715. This age is approximately 30 Ma older than the previously obtained K-Ar whole rock and Rb-Sr biotite ages, ca. 400 Ma, which represents the period of cooling. The high initial Sr isotope ratio supports the interpretation of an anatectic origin.     

Surface temperature differences between minerals in crystalline rocks: Implications for granular disaggregation of granites through thermal fatigue

Thermal expansion differences between minerals within rocks under insolation have previously been assumed to drive breakdown by means of granular disaggregation. However, there have been no definitive demonstrations of the efficacy of this weathering mechanism. Different surface temperatures between minerals should magnify thermal expansion differences, and thus subject adjacent minerals to repeated stresses that might cause breakdown through fatigue failure. This work confirms the existence of surface temperature differences between minerals in granitic rocks under simulated short-term temperature fluctuations so as to discriminate their potential for initiating granular disaggregation. The influence of colour, as a surrogate for albedo, and crystal size, as a function of thermal mass are specifically identified because of their ease of quantification. Four rock types with a range of these properties were examined, and subjected to repeated short-term temperature cycles by radiative heating and cooling under laboratory conditions. Results show that while albedo is the main control for overall and individual maximum temperatures, crystal size is the main factor controlling higher temperature differences between minerals. Thus, stones with large differences of mineral sizes can undergo magnified stresses due to thermal expansion differences.     

Rates Of Postglacial rock weathering on glacially scoured outcrops (Abisko–Riksgränsen area, 68°N)

Ice–polished quartz veins, feldspar phenocrysts and quartzite layers were used as reference surfaces to assess the impact of Postglacial rock weathering in Lapland (68°N). Over 3200 measurements were carried out on roches moutonées and glaciofluvially scoured outcrops distributed within three study areas covering 8 km². Inferred weathering rates demonstrate that 10,000 years of Holocene weathering did not significantly modify the geometry of Weichselian rock surfaces. However, rates of general surface lowering range from 1 to 25, depending on the rock type, with average values at 0.2 mm ka⁻¹ for homogeneous crystalline rocks (irrespective of their acidity and grain size), 1 mm ka⁻¹ for biotite–rich crystalline rocks, and 5 mm ka⁻¹ for carbonate sedimentary rocks. Accelerated rates were recorded in weathering pits and along joints with values up to ten times higher than on the rest of the rock surface. Comparisons with cold and temperate areas suggest that solution rates of carbonate rocks are highly dependent on climate conditions, whilst granular disintegration of crystalline rocks operates at the same rate whatever the environment. It probably means that microgelivation is not efficient on ice–polished crystalline outcrops even under harsh climate conditions, and that granular disintegration proceeds under various climates from the same ubiquitous combination of biochemical processes. Last, the weathering state of Late–Weichselian roches moutonées can be usefully compared to that of Preglacial tors of the nearby Kiruna area.     

Rates Of Postglacial rock weathering on glacially scoured outcrops (Abisko–Riksgränsen area, 68°N)

Ice–polished quartz veins, feldspar phenocrysts and quartzite layers were used as reference surfaces to assess the impact of Postglacial rock weathering in Lapland (68°N). Over 3200 measurements were carried out on roches moutonées and glaciofluvially scoured outcrops distributed within three study areas covering 8 km². Inferred weathering rates demonstrate that 10,000 years of Holocene weathering did not significantly modify the geometry of Weichselian rock surfaces. However, rates of general surface lowering range from 1 to 25, depending on the rock type, with average values at 0.2 mm ka⁻¹ for homogeneous crystalline rocks (irrespective of their acidity and grain size), 1 mm ka⁻¹ for biotite–rich crystalline rocks, and 5 mm ka⁻¹ for carbonate sedimentary rocks. Accelerated rates were recorded in weathering pits and along joints with values up to ten times higher than on the rest of the rock surface. Comparisons with cold and temperate areas suggest that solution rates of carbonate rocks are highly dependent on climate conditions, whilst granular disintegration of crystalline rocks operates at the same rate whatever the environment. It probably means that microgelivation is not efficient on ice–polished crystalline outcrops even under harsh climate conditions, and that granular disintegration proceeds under various climates from the same ubiquitous combination of biochemical processes. Last, the weathering state of Late–Weichselian roches moutonées can be usefully compared to that of Preglacial tors of the nearby Kiruna area.     

Anomalous thermal maturities caused by carbonaceous sediments

Sedimentary rocks such as coal and carbonaceous mudstone which contain abundant carbonaceous matter are characterized by thermal conductivity much lower than that exhibited by other common rock types, by a factor of 5–10. As a result, temperature gradients in such sediments can range up to 0.25 °Cm^-1 even under conditions of average heat flow. When such steep gradients extend over a significant sedimentary thickness, temperatures of underlying rock units are elevated, causing both organic and inorganic phases to record what seem to be anomalously high levels of thermal maturity. This carbonaceous blanket insulating effect may help to explain unusual levels of maturity observed at shallow depths in the Appalachian Basin, Michigan Basin and other regions of the world with significant carbonaceous strata.     

Late‐Pleistocene Wedge Structures Along the Patagonian Coast (Argentina): Chronological Constraints and Palaeo‐Environmental Implications

This paper investigates several wedge structures formed in continental deposits covering marine sediments deposited during MIS 5 along the central Patagonian coast of Argentina. The size and surface microtexture characteristics of the infilling sediments are consistent with a depositional environment dominated by aeolian transport. Fragments of Andean volcanic rocks (glass shards) in the wedge‐fill suggest long‐distance transport via a westerly component of wind direction. The wedges are interpreted as products of deep seasonal frost action in frozen ground, which produced open cracks that filled rapidly with partially non‐local aeolian sediments. Many wedges cross cut carbonate crusts that formed under permafrost conditions in coastal Patagonia. The radiocarbon dating of carbonate crusts yielded an age of 25–27 kyr bp , while wedge‐fill sediments are OSL dated to 14 670 ± 750 yr bp . This indicates that ground wedge formation occurred during a cold event (the Antarctic Cold Reversal period) that interrupted the permafrost degradation following the Last Glacial Maximum.     

Differential weathering and erosion in an inselberg landscape in southern Zimbabwe: A morphometric study and some notes on factors influencing the long-term development of inselbergs

A morphometric analysis of inselberg systems in southern Zimbabwe indicated that there are two types of inselberg systems that differ in the mode of development. Inselberg systems characterized by backwearing tend to occur on granitoid rocks that are foliated, highly fractured, and prone to grusification. The inselbergs are mostly of the koppie-type and are covered to a great extent with regolith or debris. The second type of inselbergs consists of sparsely fractured granitoid rocks, and areas underlain by these rocks are characterized by clusters of closely spaced rock domes. In the case of these inselbergs, backwearing is not indicated. They appear to be the result of the exposure of structurally pre-designed, highly resistant rock compartments.The hypothesis that differences in lithology and structure may influence the rate and style of inselberg development was tested by means of a simulation model. The simulations are run under the same boundary conditions with differing assumptions concerning role of divergent weathering. The results show that both modes of inselberg development may occur alongside one another as long as a critical relief is maintained. The modelling provided also indicates that, although the inselberg systems must have integrated several sequences of environmental changes during their development, these changes were not able to divert the general trend of the process–response system away from its steady course. Lithological and structural factors, which are responsible for the differences in the mobility of material on the inselberg sideslopes, are thus considered to be the primary source of influence of the different modes of inselberg development. It is suggested that the compositional and structural diversity in granitoid rock terrains is what enables inselbergs to pass through different development modes and sequences as rocks of differing resistance become subject to weathering during the development of the landscape.     

Analysis about the influence on the thermal regime in permafrost regions with different underlying surfaces

In the last several decades, the underlying surface conditions on the Qinghai-Tibet Plateau have changed dramatically, causing permafrost degradation due to climate change and human activities. This change severely influenced the cold regions environment and engineering infrastructure built above permafrost. Permafrost is a product of the interaction between the atmosphere and the ground. The formation and change of permafrost are determined by the energy exchange between earth and atmosphere system. Fieldwork was performed in order to learn how land surface change influenced the thermal regime in permafrost regions. In this article, the field data observed in the Fenghuo Mountain regions was used to analyze the thermal conditions under different underlying surfaces on the Qinghai-Tibet Plateau. Results show that underlying surface change may alter the primary energy balance and the thermal conditions of permafrost. The thermal flux in the permafrost regions is also changed, resulting in rising upper soil temperature and thickening active layer. Vegetation could prevent solar radiation from entering the ground, cooling the ground in the warm season. Also, vegetation has heat insulation and heat preservation functions related to the ground surface and may keep the permafrost stable. Plots covered with black plastic film have higher temperatures compared with plots covered by natural vegetation. The reason is that black plastic film has a low albedo, which could increase the absorbed solar radiation, and also decrease evapotranspiration. The ＂greenhouse effect＂ of transparent plastic film might effectively reduce the emission of long-wave radiation from the surface, decreasing heat loss from the earth＇s surface, and prominently increasing ground surface temperature.     

The Weathering of Granodiorite Porphyry in the Thiel Mountains, Inland Antarctica

The weathering of granodiorite porphyry is examined in the extremely cold and dry environment of the inland part of Antarctica. Weathering features include granular disintegration, rock varnish, and sheeting. Sheeting has gradually proceeded since the exposing of the nunatak, but the other types of weathering have not actively advanced in recent times.
Granular disintegration primarily comprises the release of individual crystals. The mechanism of this release is that cracks are created along crystal boundaries and cleavages in phenocrysts mainly due to differential thermal expansion. Plagioclase and hypersthene are released more readily than quartz. Disintegration of plagioclase has produced many prism-shaped holes, 0.5 to 2.0 mm in length, while fine-grained quartz crystals, 0.05 to 0.1 mm in diameter, are incidentally released without cracking.
The reddish brown (10R4/4) rock varnishes result from oxidation and consist of limonite, which fills cracks and penetrates into crystals. Ferrous iron in hypersthene, biotite, ilmenite and magnetite is transformed into limonite by oxidation. Manganese is not found in the varnishes. Sulfur, which is important for oxidation and which may have originated from adhered snow, is concentrated on the surface of the rock.
Sheeting has precipitated rock falls, and has gradually formed a gray mosaic on the varnished wall. The sheeting was caused by gravitational body force, which is internal stress of the rock body due to the mass of the overburden.     

Biotic weathering of rocks by lichens in Antarctica

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