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311.
肃南县羊露河上游似鞍山式铁矿地质特征及找矿方向 总被引:5,自引:0,他引:5
羊露河上游铁矿位于北祁连西段加里东褶皱带西段.铁矿体赋存于下元古界长城系上岩组含铁角闪片岩中,含矿层位严格受地层层位控制,矿石构造具有同生沉积特征,并显示了热液富集作用特点,具"似鞍山式"铁矿成因特征,矿石品位较高,盲矿体存在的可能性较大,因此具有重要的找矿意义. 相似文献
312.
313.
介绍滇中红层形成的地质历史背景,红层分布范围,主要地层岩性及区内地质构造。重点讨论滇中红层特别是红层软岩的岩体原生结构,及后期受构造改造的岩体结构特性,岩体风化特性,岩体水理作用特性,岩体物理力学性质等四方面的工程地质特性。 相似文献
314.
315.
Andrew G. Tomkins 《Mineralium Deposita》2007,42(6):627-637
The relative importance of mechanical re-mobilisation, hydrothermal dissolution and re-precipitation, and sulphide melting
in controlling redistribution of metals during concurrent metamorphism and deformation is evaluated at the middle amphibolite
facies Montauban deposit in Canada. As at many other deposits, ductile deformation was important in driving mechanical re-mobilisation
of massive sulphides from limb regions into hinge regions of large-scale folds and is thus the most important for controlling
the economics of Pb and Zn distribution. Two possible stages of hydrothermally driven re-mobilisation are discussed, each
of which produces characteristically different alteration assemblages. Prograde hydrothermal re-mobilisation is driven by
pyrite de-sulphidation and concurrent chlorite dehydration and is thus an internally driven process. At Montauban, the H2S-rich fluid generated through this process allowed re-mobilisation of gold into the wall rock, where it was deposited in
response to sulphidation of Fe Mg silicates. Retrograde hydrothermal re-mobilisation is an externally driven process, whereby
large volumes of fluids from outside the deposit may dissolve and re-precipitate metals, and cause hydration of silicate minerals.
This second hydrothermally driven process is not recognised at Montauban. Sulphide melting occurred as temperatures neared
the peak metamorphic conditions. Melting initiated in the massive sulphides through arsenopyrite breakdown, and a small volume
of melt was subsequently re-mobilised into the wall rock. Trace element partitioning and fractional crystallisation of this
melt generated a precious metal-rich fractionate, which remained mobile until well after peak metamorphism. Thus, prograde
hydrothermal re-mobilisation and sulphide melting were the most important mechanisms for controlling the distribution of Au
and Ag. 相似文献
316.
江西安远路迳金伯利质煌斑岩筒研究——一种新型的幔源碱性超基性岩 总被引:1,自引:0,他引:1
路迳岩筒属火山通道相,由金伯利质煌斑岩、角砾岩、角砾凝灰岩组成,富含幔源橄榄岩包体、普通辉石巨晶和岩球。造岩矿物是橄榄石、斜方辉石、单斜辉石、角闪石和金云母,深源特征指示矿物有镁铝榴石、铬透辉石、铬尖晶石和镁钛铁矿。岩石化学组成超低SiO2,低MgO,高Al2O3,富碱,富挥发组分。轻稀土元素富集,相容元素贫化,不相容元素明显富集。岩浆起源深度约85km。其中:岩体产状,富含包体、巨晶和岩球,岩石结构和构造,矿物组成,岩石化学组成超低SiO2、富碱、富挥发组分等特征与金伯利岩相似;但岩石化学组成高Al2O3,低MgO,K2O低于Na2O,REE和LREE/HREE偏低,部分微量元素的亏损或富集,金云母成分富TiO2,富TFeO,贫MgO,镁铝榴石、铬透辉石、铬尖晶石和镁钛铁矿的Cr2O3含量偏低,岩浆起源深度较浅,均与金伯利岩有重大差异,而更接近煌斑岩类。研究认为,是幔源岩浆岩的一种新类型,岩石名称界定为金伯利质煌斑岩。 相似文献
317.
Geoscientific Information Systems (GIS) provide tools to quantitatively analyze and integrate spatially referenced information
from geological, geophysical, and geochemical surveys for decision-making processes. Excellent coverage of well-documented,
precise and good quality data enables testing of variable exploration models in an efficient and cost effective way with GIS
tools. Digital geoscientific data from the Geological Survey of Finland (GTK) are being used widely as spatial evidence in
exploration targeting, that is ranking areas based on their exploration importance. In the last few years, spatial analysis
techniques including weights-of-evidence, logistic regression, and fuzzy logic, have been increasingly used in GTK’s mineral
exploration and geological mapping projects. Special emphasis has been put into the exploration for gold because of the excellent
data coverage within the prospective volcanic belts and because of the increased activity in gold exploration in Finland during
recent years. In this paper, we describe some successful case histories of using the weights-of-evidence method for the Au-potential
mapping. These projects have shown that, by using spatial modeling techniques, exploration targets can be generated by quantitatively
analyzing extensive amounts of data from various sources and to rank these target areas based on their exploration potential. 相似文献
318.
将中国沿海省区17个中心城市服务业水平分为全面发展型、发达型、次发达型和欠发达型。通过服务业以及服务业与城市之间的关系分析得出:发达型、次发达型服务业的人均服务产品占有量与增加值比重以及就业比重均呈正相关关系,且相关性随着服务业绝对水平的提高而增强;欠发达型服务业的人均服务产品占有量与增加值比重以及就业比重均呈负相关的关系;任何水平类型的服务业的增加值比重与就业比重之间都为正相关。服务业绝对水平与城市人均GDP、城市综合竞争力、城市规模之间都呈正相关;比重规模与城市经济水平之间无明显相关性。 相似文献
319.
Andrs Folguera Víctor A. Ramos Toms Zapata Mauro G. Spagnuolo 《Journal of Geodynamics》2007,44(3-5):129-148
The Andes between 36°30′ and 37°S represent a Cretaceous fold and thrust belt strongly reactivated in the late Miocene. Most of the features that absorbed Neogene shortening were already uplifted in the late Cretaceous, as revealed by field mapping and confirmed by previous fission track analysis. This Andean section is formed by two sectors: a western-inner sector generated by the closure of the upper Oligocene-lower Miocene intra-arc Cura Mallín basin between the middle and late Miocene (Guañacos fold and thrust belt), and an eastern-outer sector, where late Triassic-early Jurassic extensional depocenters were exhumed in two discrete phases of contraction, in the latest early Cretaceous and late Miocene to the Present, respectively (Chos Malal fold and thrust belt). Late Miocene deformation has not homogeneously reactivated Cretaceous compressive structures, being minimal south of 37°30′S through the eastern-outer sector (southern continuation of the Chos Malal fold and thrust belt). The reason for such an inhomogeneous deformational evolution seems to be related to the development of a late Miocene shallow subduction regime between 34°30′ and 37°45′S, as it was proposed in previous studies. This shallow subduction zone is evidenced by the eastward expansion of the arc that was accompanied by the eastern displacement of the orogenic front at these latitudes. As a result, the Cretaceous fold and thrust belt were strongly reactivated north of 37°30′S producing the major topographic break along the Southern Central Andes. 相似文献
320.
The Tibesti massif, one of the most prominent features of the Sahara desert, covers an area of some 100,000 km2. Though largely absent from scientific inquiry for several decades, it is one of the world’s major volcanic provinces, and
a key example of continental hot spot volcanism. The intense activity of the TVP began as early as the Oligocene, though the
major products that mark its surface date from Lower Miocene to Quaternary (Furon (Geology of Africa. Oliver & Boyd, Edinburgh
(trans 1963, orig French 1960), pp 1–377, 1963)); Gourgaud and Vincent (J Volcanol Geotherm Res 129:261–290, 2004). We present here a new and consistent analysis of each of the main components of the Tibesti Volcanic Province (TVP), based
on examination of multispectral imagery and digital elevation data acquired from the Advanced Spaceborne Thermal Emission
and Reflection Radiometer (ASTER). Our synthesis of these individual surveys shows that the TVP is made up of several shield
volcanoes (up to 80 km diameter) with large-scale calderas, extensive lava plateaux and flow fields, widespread tephra deposits,
and a highly varied structural relief. We compare morphometric characteristics of the major TVP structures with other hot
spot volcanoes (the Hawaiian Islands, the Galápagos Islands, the Canary and Cape Verdes archipelagos, Jebel Marra (western
Sudan), and Martian volcanoes), and consider the implications of differing tectonic setting (continental versus oceanic),
the thickness and velocity of the lithosphere, the relative sizes of main volcanic features (e.g. summit calderas, steep slopes
at summit regions), and the extent and diversity of volcanic features. These comparisons reveal morphologic similarities between
volcanism in the Tibesti, the Galápagos, and Western Sudan but also some distinct features of the TVP. Additionally, we find
that a relatively haphazard spatial development of the TVP has occurred, with volcanism initially appearing in the Central
TVP and subsequently migrating to both the Eastern and Western TVP regions.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献