共查询到20条相似文献，搜索用时 46 毫秒
1.
Environments characterized by fluctuating hypersaline to fresh-water conditions are defined as “schizohaline” and examples are given of situations in which “schizohaline” environments can arise. Fabrics diagnostic for the occurrence of both hyper- and hyposalinity have been recorded in Late Paleozoic rocks from Bear Island (74°30′N, 19°E): evaporite nodules, length-slow chalcedony and very finely crystalline penecontemporaneous dolomite are considered as indicators of hypersaline conditions while euhedral limpid dolomite crystals, coarse poikilitic sparry calcite and microspar calcite are thought to have originated under the hyposaline regime. Zoned dolomite crystals and euhedral crystals of authigenic mega-quartz replacing sulphates have also been recorded in the same rocks; their diagnostic importance for the schizohaline environment is, however, uncertain.Internal structural pores of some crinoid and bryozoan skeletal grains of biosparites from Bear Island are either empty or infilled with very finely crystalline dolomite. Expulsion of Mg2+ ions from the magnesian-calcite skeletons and either: (1) “poisoning” of the micro-environment of the pores; or (2) formation of stagnant “micro-sabkha” conditions in the pores are proposed as an explanation for these phenomena. 相似文献
2.
The occurrence of water in natural opaline silicas has been studied by differential thermal analysis, thermogravimetric analysis, infra‐red analysis and nuclear magnetic resonance. The results show that in the “crystalline” opals studied, some 90 per cent or more of the total water is physically adsorbed whereas in “amorphous” opals, at least 20 per cent but perhaps much more of the total water is held as hydroxyl groups chemically bonded to the silica surface. The rate of water loss on heating is also different, being chiefly controlled by the pore structure in “crystalline” opals but to a significant extent by the surface structure in “amorphous”. 相似文献
3.
Prof. Dr. Erwin Nickel Dr. Marino Maggetti 《International Journal of Earth Sciences》1974,63(2):618-654
The genesis of synorogeneous, variscian magmatites from the Bergsträsser Odenwald is explained. They are alternating with steep, old metamorphic rocks (schists and schisteous gneisses, partly transformed to plagioclase-blastites). The magmatites are differentiated into an early-orogenic hornblende-basiteseries (gabbro → diorite) and a high-orogenic biotite-flasermagmatite-series (diorite → granite). The hornblende-basite-series is “normally intrusive” with differentiated syntectic members; the biotite-flasermagmatite-series is lithogenic and has been formed by plagioclase-blastesis and anatexis. At the transition to the high-orogenic phase the rocks develop a strong gneissose foliation (due to movements during the emplacement). The structures assimilate, and a protoclastic to primary-gneissic texture is formed. We name the crystalline in this periode of formation briefly “Synorogen”. The diorites from the two series, as well as the dioritoids and aorites (products of “dioritisation”) show converging structures within the Synorogen. The mobile (ultrametamorphic) stage during the dioritisation and granitisation is discussed. 相似文献
4.
《International Geology Review》2012,54(1):78-83
Recent and detailed seismic studies in the U.S.S.R. have provided much information on the structure and revolution of the earth's crust. A review of this information indicates the following postulates: a) the thickness and constitution oft he crystalline layers (”basalt“ and ”granite“) change comparatively rapidly in Alpine provinces of pronounced tectonic movements (geosynclinal provinces and mobile zones), with but a slight lag behind these movements. b) Under platform areas, the crystalline complexes rebuild slowly with a lag of a few geologic periods behind the emergence of the structural elements. c) In both geosynclinal and platform areas the downwarping of the major segments is accompanied by an upward movement of the Mohorovi?i? surface. d) Block uplifts in geosynclinal provinces of mobile zones have absolute values, while in platform areas the uplifts usually represent blocks lagging behind their neighbors. e) Changes in thickness and composition of deeper layers within the crust usually lag behind the formation of corresponding structural elements. — J. R. Hayes 相似文献
5.
The mineral assemblage and the sedimentological characteristics of the “Donauplatin” (Danubian fluvial placer containing platinum-group elements (PGE) and gold (Au)) are described for the first time in connection with upstream reference placer deposits near the potential source area in tributaries of the River Danube/Donau. Granulometric and morphometric data have been obtained using the CCD-based CAMSIZER technique. The platinum-group minerals (PGM; iridium, osmium, unknown iridium-osmium-sulfide, ruthenium-osmium-iridium alloys, platinum-iron alloys, iridium-bearing platinum, sperrylite) have been derived from ultramafic magmatic rocks, probably belonging to the ophiolitic series in the Tepla Barrandian unit of the Bohemian Massif. The Au-Pd-Cu compounds in the placer originated from dynamo-metamorphogenic processes in a sulfur-deficient environment at the SW edge of the Bavarian Basement. Gold in the “Donauplatin” has been reworked from a “secondary” or intermediate repository of lateritic gold (Boddington-type). Its primary source is supposed to be of orogenic origin. Provenance analyses of the associated non-heavy minerals point to high-pressure metamorphic rocks, igneous rocks (monazite) and high-temperature metamorphic rocks (750° to 850°C, zircon morphology). Garnet compositions indicate that meta(ultra)basic igneous rocks, calc-silicate rocks and skarns prevailed over paragneisses in the provenance area. Extraterrestrial processes creating the well-known Ries impact crater in the environs of Nördlingen during the Miocene have a minor share in the PGE budget by delivering molybdenum-ruthenium-osmium-iridium alloys and iridium solid-solution series (s.s.s.) minerals. Judging by the heavy mineral suites, Saxothuringian source rocks of the NE Bavarian Basement connected with the Donau River via the Naab River drainage system have not contributed to the element budget of the “Donauplatin” under study. Stream sediments which have been derived from this provenance area are characterized by low-temperature (LT) crystalline rocks and a considerable proportion of pegmatitic and metabauxitic material lacking in the Holocene sediments of the “Donauplatin”. 相似文献
6.
《International Geology Review》2012,54(12):1145-1149
Evidence of “Upper Cretaceous” sediments above the melt rock/breccia assemblage at Chicxulub has been used to dispute the link between this large impact crater and the Cretaceous-Tertiary (KT) extinction horizon. We have evaluated core samples and well logs from the Petróleos Mexicanos (Pemex) Yucatan No. 6 exploratory well located ～50 km from ground zero. Despite previous reports to the contrary, the sequence of crystalline rocks and breccias located at depths exceeding 1000 m below sea level are characteristic of the upper lithological sequence observed at other large impact basins such as the 220 km Sudbury structure. Furthermore, the “Upper Cretaceous” sediments overlying the melt rocks and impact brecias at Chicxulub contain abundant glass shards and shocked minerals, demonstrating conclusively that these are reworked debris involved in the impact event, and not normal marine sediments. Core samples straddling the KT boundary indicate that the impact event created a basin several hundred meters deep. 相似文献
7.
Groundwater resources in the semi-arid regions of southern India are under immense pressure due to large-scale groundwater abstraction vis-à-vis meager rainfall recharge. Therefore, understanding and evaluating the spatial distribution of groundwater is essential for viable utilization of the resource. Here, we assess groundwater potential at the watershed scale, in a semi-arid environment with crystalline aquifer system without a perennial surface water source using remote sensing, geophysical, and GIS-based integrated multi-parameter approach. GIS-based weighed overlay analysis is performed with input parameters, viz., geology, geomorphology, lineament density, land use, soil, drainage density, slope, and aquifer thickness. The watershed is categorized into four zones, namely, “very good” (GWP4), “good” (GWP3), “moderate” (GWP2), and “low” (GWP1) in terms of groundwater potential. Overall, ~?70% of the study area falls under moderate to low groundwater potential, indicating a serious threat to the future availability of the resource. Therefore, serious measures are required for maintaining aquifer resilience in this over-exploited aquifer (e.g., restricting groundwater withdrawal from GWP1 and GWP2 zones). Further, as the aquifer is under tremendous anthropogenic pressure, rainwater harvesting and artificial recharge during monsoon are advocated for sustainable aquifer management. Due to the direct dependence of crop production vis-à-vis farmer economy on groundwater, this study is an important step towards sustainable groundwater management and can be applied in diverse hydrological terrains. 相似文献
8.
基于SPA的喀斯特地区水安全评价——以贵州省为例 总被引：6，自引：5，他引：1
根据目前公认的水安全内涵,将水安全分为三个子系统。水资源子系统、水环境子系统和水灾害子系统。三者相互联系、相互作用,形成了复杂、时变的水安全系统。基于水安全的基本原理和喀斯特区域特有的水循环机理,依据 “驱动力（D）—压力（P）—状态（S）—影响（I）—响应（R）”模型建立了贵州省喀斯特区域水安全评价指标体系。基于集对分析理论,引入能够体现系统确定性和不确定性的同异反联系度计算公式,建立了城市水安全的评价模型。将集对分析法运用到水安全的评价中, 可以先通过计算评价样本与评价指标之间的联系度对样本作初步的排序, 再对样本作进一步的同一、差异、对立的集对分析,以判断出评价样本的等级。研究结果表明:（1）在水资源安全状态方面,贵州省9个州市中4个处于安全状态,2个处于基本安全状态,2个处于不安全状态,1个处于危机状态;（2）在水环境安全状态方面,2个处于安全状态,4个处于基本安全,3个处于不安全;（3）在水灾害安全状态方面,1个处于非常安全,4个处于安全,1个处于基本安全,2个处于不安全,1个处于危机;（4）在水安全综合状态下,有3个处于安全状态,有4个处于基本安全状态,有2个处于不安全状态,没有处于非常安全和危机状态。 相似文献
9.
This paper presents new major and trace element data from 150 garnet xenocrysts from the V. Grib kimberlite pipe located in the central part of the Arkhangelsk diamondiferous province (ADP). Based on the concentrations of Cr2O3, CaO, TiO2 and rare earth elements (REE) the garnets were divided into seven groups: (1) lherzolitic “depleted” garnets (“Lz 1”), (2) lherzolitic garnets with normal REE patterns (“Lz 2”), (3) lherzolitic garnets with weakly sinusoidal REE patterns (“Lz 3”), (4) lherzolitic garnets with strongly sinusoidal REE patterns (“Lz 4”), (5) harzburgitic garnets with sinusoidal REE patterns (“Hz”), (6) wehrlitic garnets with weakly sinusoidal REE patterns (“W”), (7) garnets of megacryst paragenesis with normal REE patterns (“Meg”). Detailed mineralogical and geochemical garnet studies and modeling results suggest several stages of mantle metasomatism influenced by carbonatite and silicate melts. Carbonatitic metasomatism at the first stage resulted in refertilization of the lithospheric mantle, which is evidenced by a nearly vertical CaO-Cr2O3 trend from harzburgitic (“Hz”) to lherzolitic (“Lz 4”) garnet composition. Harzburgitic garnets (“Hz”) have probably been formed by interactions between carbonatite melts and exsolved garnets in high-degree melt extraction residues. At the second stage of metasomatism, garnets with weakly sinusoidal REE patterns (“Lz 3”, “W”) were affected by a silicate melt possessing a REE composition similar to that of ADP alkaline mica-poor picrites. At the last stage, the garnets interacted with basaltic melts, which resulted in the decrease CaO-Cr2O3 trend of “Lz 2” garnet composition. Cr-poor garnets of megacryst paragenesis (“Meg”) could crystallize directly from the silicate melt which has a REE composition close to that of ADP alkaline mica-poor picrites. P-T estimates of the garnet xenocrysts indicate that the interval of ～60–110 km of the lithospheric mantle beneath the V. Grib pipe was predominantly affected by the silicate melts, whereas the lithospheric mantle deeper than 150 km was influenced by the carbonatite melts. 相似文献
10.
《China Geology》2018,1(3):425-434
The demand for graphite resources has been increasing due to its extensive use. Graphite deposits in China are mainly distributed in Heilongjiang, Innner Mogolia, Sichuan, Shanxi and Shandong, characterized by “one old & one new” and “many in east & few in west”. There are mainly three genetic types, including regional metamorphic type, contact metamorphic type and hydrothermal type. Here we provide a summary of the metallogenic regularity and 15 metallogenic belts in China based on the study of the geology of national graphite deposits. In recent years, great progress has been made in the research of genesis, mineral exploration and evaluation on graphite deposits, which indicate great potential for graphite resource in China. The authors suggest that the research on geochronology, ore sources, the genesis of crystalline graphite and exploration for hydrothermal graphite in China should be heightened. 相似文献
11.
Collision can be subdivided into “soft” and “hard” types, with the “soft” collision occurring after double-sided oceanic subduction and the “hard” collision after single-sided oceanic subduction. Although two types of collision involve different geodynamics and generate distinct petrological assemblages, whether they can preserve distinct records of detrital zircons remains unclear. This study confirms “soft” collision between the north Western Kunlun terrane (NKT) and the south Western Kunlun terrane (SKT) after the closure of the Proto-Tethys Ocean. We further compare detrital zircon Hf isotope compositions of the “soft” collision with those of the “hard” collision related to the amalgamation of Rodinia in southern Tarim. Our results show that the NKT is characterized by dominant ca. 800 Ma zircons, whereas the SKT is featured by ca. 244 Ma, ca. 440 Ma, and ca. 620 Ma zircons. As such, sample 17WP53 deposited at 431 Ma in the NKT displays a dominant peak at ca. 500 Ma, indicating minor material exchange between the NKT and the SKT at ca. 431 Ma. Given the 420–405 Ma North Kudi granites displaying geochemical features of within-plate granites formed at a post-orogenic stage, we infer that the final closure of the Proto-Tethys Ocean occurred at 431–420 Ma along Western Kunlun. Moreover, zircon εHf(t) data indicate that the “soft” collision between the NKT and the SKT during the amalgamation of Gondwana produced ca. 40% of juvenile crustal materials, whereas the “hard” collision related to the formation of Rodinia generated ca. 12% of juvenile crustal materials. More juvenile materials generated in the “soft” collision may be attributed to complete detachment and sinking of a oceanic slab. 相似文献
12.
K. L. Burns 《Mathematical Geosciences》1975,7(4):295-321
Geological events, such as emplacement of granite or growth of slaty cleavage, may be ordered into a sequence by two methods. One is to assign each event a place in a time scale, such as years before the present, which amounts to assigning events an age designation from the set of real numbers. In ordering such a list, the algebra of real numbers applies. A second method is to determine the time relations of events in pairs, such as a fold is of type (S1, S2) or granite intrudes conglomerate. These binary relations between events may be used to order events into a sequence using the transitive properties of the relation “older than.” It is shown, however, that the binary relations between events do not follow the familiar rules for the algebra of real or integral numbers and it is necessary to erect a new system of relations called the “algebra of events.” The fundamental relation is “older than or equivalent to” and this may be used to define the relations “older than”, “younger than”, “equivalent to”, “incomparable to”, and “covers.” The essential difference from the algebra of integers is that the reflexive relation (“equal to”) is replaced by two such relations (“equivalent to” and “incomparable to”) in the algebra of events. A number of binary relations between events may be assembled into an event matrix which is basically a truth table for the relation “older than.” This may be ordered and stacked by operations termed ORDER and STACK. The relationship of each event to every other event may be determined by simple inspection of an ordered, stacked matrix, and from this a geological history may be assembled. If there are contradictions in the field data, ordering into a proper sequence is impossible and may be detected. If there are ambiguities in the field data, there are several different orders that are proper sequences so that the event matrix may be ordered. However, the ambiguities occur as voids in the stacked matrix. 相似文献
13.
14.
Evidence for a Long-Term Strength Threshold in Crystalline Rock 总被引：3，自引：1，他引：2
The mechanical response of brittle rock to long-duration compression loading is of particular concern in underground disposal of nuclear waste, where radionuclides must be isolated from the biosphere for periods of the order of a million years. Does the strength decrease without limit over such time, or is there, for some rock types, a lower “threshold” strength below which the rock will cease to deform? This paper examines the possibility of such a threshold in silicate crystalline rocks from several perspectives, including: (1) interpretation of the results of short-term creep tests on rock; (2) numerical analysis of the effect of decrease in fracture toughness due to stress corrosion on the strength of a crystalline rock; and (3) evidence from plate tectonics, and observations of in situ rock stress in granite quarries. The study concludes that there is clear evidence of threshold strength. The threshold is of the order of 40% of the unconfined compressive strength or higher for laboratory specimens under unconfined compressive loading, and increases rapidly in absolute value with confinement. Field evidence also leads to the conclusion that the long-term strength of crystalline rock in situ is of comparable magnitude to the laboratory value. 相似文献
15.
Prof. Dr. Horst Bögek 《International Journal of Earth Sciences》1983,72(3):771-813
Research carried out on lacustrine Gastropods of Neogene age from sediments of continental faciès (“molasse”) on some Aegean islands (Kos, Rhodes, Naxos, Eremonisia, Makares, Paros, Anaphi, Crete, Samos, Chios, Euboea) led to the conclusion that certain strata are much older than hitherto suggested. During Serravallian and Tortonian times limnic and fluviatile sediments must have been by far more widespread in the Aegean Region than earlier supposed. It can be shown furthermore that most of these older series of sediments south of the ?Medean Christalline Belt” and on the top of the ?Attic-Cycladic Complex” are allochthonous or parautochthonous. They obviously became involved in movements of the “Central” and “Western Hellenic Nappes” as defined byJacobshagen et al., 1978. Similar events in the Northern Apennines are known by the catchword “Loiano-Effect”. During Tortonian times decoupling occured within these nappe piles. Subunits consisting in part of Neogene strata, sometimes still connected to their ophiolitic basement, started to move separately into northern (Cyclades) or southern (Kos-Island) directions. A compounded nappe, in this paper called “Aegean Nappe”, consisting of parts of the “Pelagonian Nappe”, the “Ophiolite Nappe” and slices of the “molasse”-series emerged. Locally marine sediments of Lower to Middle Miocene age suggested to be autochthonous were overthrust or cut up in front of the moving nappe (Kos, Rhodes). On some islands of the Cyclades (Naxos, Paros, Eremonisia, Makares, Mykonos) remnants of the “Aegean Nappe” rest on top of the “Lower Unit” of the “Attic-Cycladic complex” as defined byAltherr et al., 1979, and are equivalent to the “Upper Unit” of authors. The paroxysm of those decouplings happened during the upper Tortonian (8–10 Ma); it presumably influenced sedimentary processes of that time on Crete. The view is taken that the movements of nappes were caused by local crustal rising and, hence, gravity controlled. 相似文献
16.
Glenn B. Stracher 《Mathematical Geosciences》1995,27(4):499-511
Coal seams and culm banks associated with mine fires in the anthracite region of eastern Pennsylvania have been burning for decades. Many of the fires may have ignited by spontaneous combustion or by the burning of trash. Minerals associated with the combustion of anthracite form by the condensation of gas exhaled through surficial gas vents or “anthracite smokers.” A Pressure-Temperature (P-T) stability diagram is constructed for the condensation of orthorhombic sulfur from anthracite gas using “Thermodynamic Loop Analysis” (TL analysis). This method of analyzing chemical systems incorporates Kirchhoff's Law into a four step procedure structured around a closed thermodynamic cycle or “thermodynamic loop.” The four steps, referred to us “The Four S ′S of Thermodynamic Loop Analysis,” include: (1) “Set Up”—graphical characterization of the problem. (2) “Sum”—the application of thermodynamic principles. (3) “Substitute”—the use of materials data available from the literature, and (4) “Solve”—computation of one or more variables. The example presented demonstrates that thermodynamic loops can incorporate any number of polymorphic phase transformations. In addition, thermodynamic loop analysis is applicable to any geologic process involving the condensation of minerals from a gas. The stability diagram derived by TL analysis may have applicability in monitoring the release of sulfur gas into the atmosphere. 相似文献
17.
Diagenesis of metal-organic complexes in sediments: Formation of metal sulphides from cystine complexes 总被引：1，自引：0，他引：1
J.D. Saxby 《Chemical Geology》1973,12(4):241-248
Metal-cystine complexes of iron, lead, zinc, copper and nickel under mild artificial diagenesis give rise to crystalline metal sulphides and insoluble organic matter as well as gaseous and “oily” organic products. Under confined reducing conditions at 200°C for 100 h a virtual 100% conversion of metal complex to metal sulphide occurs, while < 10% of the associated organic material may remain as kerogen. Such a mechanism could account for the formation of metal sulphides and in particular pyrite from protein- or amino acid-rich material in carbonaceous sediments during diagenesis. 相似文献
18.
受界面效应影响,毛细水在层状土中运移规律还难以用描述均质土中水分运移规律的Lucas-Washburn（LW）渗吸模型进行描述。基于此,本文设计了层状土室内模型试验,采用分布式的主动加热光纤法（简称AHFO）监测毛细水上升过程。根据AHFO测试结果,进一步对LW模型进行了修正,提出了适用于描述层状土中毛细水上升规律的ILW模型,并对ILW模型进行了试验验证。试验结果表明:（1）当毛细水湿润锋抵达“黏土（下部）-砂土（上部）”界面时,会产生“毛细屏障作用”,从而导致上部砂土中毛细水含水率急剧下降;（2）“毛细屏障作用”由砂土和黏土中的基质吸力不均衡造成,基质吸力大小由含水率决定;（3）当毛细水湿润锋抵达“砂土（下部）-黏土（上部）”界面时,在界面处出现“反毛细屏障作用”,从而导致上部黏土层中的含水率比相邻下部砂土层含水率更高;（4）虽然常见的LW模型可准确预测均质土中毛细水上升高度及速率,但受“毛细屏障作用”和“反毛细屏障作用”影响,LW模型在层状土中失效;（5）相比LW模型,ILW模型精度更高,能够更加准确地描述层状土中毛细水上升规律。 相似文献
19.
《Comptes Rendus Geoscience》2014,346(9-10):262-272
New radiometric data from recent cartographic projects (2007, 2010) lead to a re-interpretation of the “Koubia–Lessere Unconformity” (KLU). This unconformity is evidenced in the Bassaride Ranges (northern Guinea) and in two western inliers (Tominé and Kemberra). The KLU was previously correlated with the main unconformity (Jbeliat unconformity [JU]) separating the lower “super group 1” from the middle “super group 2” of the large Taoudeni basin. Consequently, the brecciated level (partly glaciogenic) that underlines the “KLU” was correlated with the “tillitic” level located at the base of the super group 2. The latter is linked to the worldwide “Marinhoan” glacial event (650–635 Ma). However, 32 recently published U/Pb age data on detrital or new formed zircons show clearly that the Bassarides groups (ante KLU), deformed and slightly metamorphosed by the Panafrican-II orogen, belong to the super group 2 of the Taoudeni basin. Consequently, the overlying “Koubia–Lessere unconformity” (KLU) cannot be linked to the “Jbeliats unconformity” (JU) that separates the super groups 1 and 2 in the Taoudeni basin. The KLU is younger than the Panafrican-II orogen and probably younger than the last volcanic basaltic flows (492 Ma) outcropping in the Bassaride belt. Consequently, the glaciogenic levels that outcrop in the KLU should be distinguished from the numerous “Marinhoan” glacial levels of West Africa. This new KLU interpretation implies some important changes in the stratigraphic correlations and interpretations all over the West African domain. 相似文献
20.
大型矿床和成矿区(带)在混沌边缘 总被引：26，自引：8，他引：18
笔者将复杂性科学和矿床地质学相结合提出了一种新的金属成矿理论———“金属成矿动力系统的复杂性与自组织临界性”,并应用这一理论研究扬子古陆周缘四大成矿区（带）的矿床成因与成矿规律,发现“大型矿床和成矿区（带）在混沌边缘”。文章在概述“金属成矿动力系统的复杂性与自组织临界性”的理论纲要与噪声、混沌和混沌边缘基本概念的基础上,提出地质成矿系统在混沌边缘的四条判定准则：Ⅰ．自组织临界性的标志———广义地质学（地质学、地球物理学、地球化学）场（温度、流速、浓度、压力等场）的场量之时空幂律分布———及其基本属性：（１）长程时空关联与连通性及时空分形结构;（２）崩塌动力学;（３）“元胞自动机”的动力学机制;（４）自组织临界性涌现于“混沌边缘”,并具有最大的复杂性、演化性和创新性。Ⅱ．地质成矿过程向时间混沌及地质成矿系统向时空混沌的演化。Ⅲ．岩浆和热液“孤子”、“孤波”与“相干结构”以及其它弱混沌“拟序结构”。Ⅳ．超临界地质流体参与地质成矿作用。笔者进一步提出金属成矿动力系统的复杂性与自组织临界性的三大基础理论：（１）地质成矿过程的非线性动力学———应用非线性动力学理论研究矿床和矿集区形成的动力学机制;（２）“地质成矿作用? 相似文献