全文获取类型
收费全文 | 47篇 |
免费 | 5篇 |
国内免费 | 16篇 |
专业分类
地球物理 | 11篇 |
地质学 | 54篇 |
综合类 | 2篇 |
自然地理 | 1篇 |
出版年
2020年 | 2篇 |
2019年 | 1篇 |
2017年 | 2篇 |
2016年 | 1篇 |
2014年 | 1篇 |
2013年 | 2篇 |
2012年 | 1篇 |
2011年 | 2篇 |
2010年 | 3篇 |
2009年 | 2篇 |
2008年 | 6篇 |
2007年 | 3篇 |
2006年 | 7篇 |
2004年 | 8篇 |
2003年 | 1篇 |
2002年 | 7篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
排序方式: 共有68条查询结果,搜索用时 31 毫秒
1.
A particular variety of volcanogenic country rock breccia is described; a contact breccia that has been identified at Venetia, River Ranch and Wimbledon kimberlite pipes. The contact breccia is clast supported with no juvenile kimberlite component, has tightly packed, angular fragments (with occasional rounding of smaller particles), and has a shear-fabric dipping towards the center of each kimberlite pipe or volcanic event. Clasts have preferred orientations parallel to the fabric. Photographs of the breccia in the open pit face and measured data from drill core are analyzed specifically to quantify the clast size distributions and clast shapes by means of fractal analysis. The fractal dimension is one means of characterizing the breccia because the dimension can be specific to a fragmentation mechanism. Clast size distribution fractal dimensions in the coarser particles (greater than circa 3 cm) range from greater than 3 for nonsheared breccia, down to circa 2.3 for the sheared breccia. Breccia characterization based on this fractal analysis suggests that fragmentation occurred initially from confined high-energy explosions, followed by collapse and abrasion by subsequently gravity-induced rockmass subsidence. All studied contact breccias produced a distinctive fractal signature in the finer particles (<3 cm) of circa 1.6 that can be explained by a comminution fragmentation process in that particular particle size range. It is suggested that these subsidence breccias require a substantial volume deficit at depth within the volcanic pipe in order to explain their origin and size. The methodology used in this study could be used to characterize any other volcanic breccia and further model their origins. 相似文献
2.
Deformation structures in the wall rocks of igneous intrusions emplaced at shallow crustal depths preserve an important record of how space was created for magma in the host rocks. Trachyte Mesa, a small Oligocene age intrusion in the Henry Mountains, Utah, is composed of a series of stacked tabular, sheet-like intrusions emplaced at 3–3.5 km depth into sandstone-dominated sedimentary sequences of late Palaeozoic–Mesozoic age. New structural analysis of the spatial distribution, geometry, kinematics and relative timings of deformation structures in the host rocks of the intrusion has enabled the recognition of distinct pre-, syn-, and late-stage-emplacement deformation phases. Our observations suggest a two-stage growth mechanism for individual sheets where radial growth of a thin sheet was followed by vertical inflation. Dip-slip faults formed during vertical inflation; they are restricted to the tips of individual sheets due to strain localisation, with magma preferentially exploiting these faults, initiating sill (sheet) climbing. The order in which sheets are stacked impacts on the intrusion geometry and associated deformation of wall rocks. Our results offer new insights into the incremental intrusion geometries of shallow-level magmatic bodies and the potential impact of their emplacement on surrounding host rocks. 相似文献
3.
Constraining the process by which volcanoes become unstable is difficult. Several models have been proposed to explain the
driving forces which cause volcanic edifices to catastrophically collapse. These include models for destabilisation of volcanic
flanks by wedging due to dyke intrusion and the weakening of mechanical properties by pressurisation of pore fluids. It is
not known which, if any, of the models are relevant to particular sector collapse events. Recent developments in the palaeomagnetic
estimation of emplacement temperatures of volcaniclastic rocks have shown that even relatively low emplacement temperatures
can be recorded by volcaniclastics with high fidelity. We have carried out a palaeomagnetic study of emplacement temperatures
to investigate the role of igneous activity in the initiation of the 9,500 b.p. Murimotu sector collapse of Mt Ruapehu, New Zealand. This debris avalanche deposit has three fades which are stratigraphically
superimposed, and the lowermost fades contains three lithological assemblages representing different segments of the edifice
which were transported with little internal mixing within the flow. We have determined that some of the dacite-bearing assemblage
1, fades 1 was hot (∼350 °C) during transport and emplacement, whereas none of the other lithological assemblages of fades
contained hot material. Our interpretation is that a dacite dome was active on the ancient Ruapehu edifice immediately prior
to the Murimotu sector collapse. The partially cooled carapace of the dome and material shed from this part was incorporated
into the avalanche deposit, along with cold lavas and volcaniclastics. We have not found evidence for incorporation of material
at or close to magmatic temperatures, at least in the sampled locations. Our palaeomagnetic work allows us to develop a comprehensive,
new palaeomagnetic classification of volcaniclastics.
Published online: 25 January 2003
Editorial responsibility: D. Dingwell 相似文献
4.
5.
就位机制问题是花岗岩地区工作的一个重点,一般来说,一个花岗岩单元,其各侵入体应该具有统一的就位机制,然而事实并非如此,葛家大窝子单元就是一个例外,本文阐述了葛家大窝子单元综合地质特征相同的不同浸入体,其就位机制不同的情况,并对其成因进行了初步探讨。 相似文献
6.
7.
Kryštof Verner Jiří Žák Jaroslava Pertoldová Josef Šrámek Jiří Sedlák Jakub Trubač Patricie Týcová 《International Journal of Earth Sciences》2009,98(3):517-532
The Plechy pluton, southwestern Bohemian Massif, represents a late-Variscan, complexly zoned intrusive center emplaced near
the crustal-scale Pfahl shear zone; the pluton thus provides an opportunity to examine the interplay among successive emplacement
of large magma batches, magmatic fabric acquisition, and the late-Variscan stress field associated with strike-slip shearing.
The magmatic history of the pluton started with the emplacement of the porphyritic Plechy and Haidmühler granites. Based on
gravity and structural data, we interpret that the Plechy and Haidmühler granites were emplaced as a deeply rooted, ∼NE–SW
elongated body; its gross shape and internal fabric (steep ∼NE–SW magmatic foliation) may have been controlled by the late-Variscan
stress field. The steep magmatic foliation changes into flat-lying foliation (particularly recorded by AMS) presumably as
a result of divergent flow. Magnetic lineations correspond to a sub-horizontal ∼NE–SW finite stretch associated with the divergent
flow. Subsequently, the Třístoličník granite, characterized by steep margin-parallel magmatic foliation, was emplaced as a
crescent-shaped body in the central part of the pluton. The otherwise inward-younging intrusive sequence was completed by
the emplacement of the outermost and the most evolved garnet-bearing granite (the Marginal granite) along the southeastern
margin of the pluton.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
8.
《International Geology Review》2012,54(3):189-215
This paper is a synthesis of structural and geochronological data from eastern Mediterranean ophiolitic metamorphic rocks and surrounding units to interpret the intra‐oceanic subduction and ophiolite emplacement mechanism. Metamorphic rocks occur as discontinuous tectonic slices at the base of the ophiolites, generally between the peridotite tectonites and volcanic‐sedimentary units, and locally in fault zones in the overlying peridotites. They consist essentially of amphibolite, and in lesser quantities, micaschist, quartzite, epidotite and marble. Geological and geochronological data indicate that recrystallization of the metamorphic rocks occurred in the oceanic environment. The contact between the metamorphic rocks and the hanging‐wall is parallel to the foliation of the metamorphic rocks, and is interpreted as the fossil plane of intra‐oceanic subduction. Structural relationships suggest that intra‐oceanic subduction was situated between two lithospheric blocks separated by an oceanic fracture zone. Therefore the Neotethyan ophiolites with metamorphic soles represent the remnants of the overriding oceanic lithosphere's training slices of the metamorphic rocks at the base. In the Anatolian region, radiometric dating of metamorphic rocks from the Taurus and Izmir‐Ankara‐Erzincan zone ophiolites yield nearly identical ages. Besides, palaeontological and structural data indicate coeval opening and similar oceanic ridge orientation. Consequently it is highly probable that Taurus and Izmir‐Ankara‐Erzincan zone ophiolites represent fragments of the same oceanic lithosphere derived from a single spreading zone. Palaeontological data from underlying volcanic and sedimentary units point out that the opening of the Neotethyan ocean occurred during Late Permian‐Middle Triassic time in the Iranian‐Oman region, during Middle Triassic in Dinaro‐Hellenic area, and finally during Late Triassic in the Anatolian region. Radiometric dating of the metamorphic rocks exhibit that the intra‐oceanic thrusting occurred during late Lower‐early Late Jurassic for Dinaro‐Hellenic ophiolites, late Lower‐early Late Cretaceous for Anatolian, Iranian and Oman ophiolites well before their obduction on the Gondwanian continent. Neotethyan ophiolites were obducted onto various sections of the Gondwanian continent from late Upper Jurassic to Palaeocene time, Dinaro‐Hellenic ophiolites during late Upper Jurassic‐early Lower Cretaceous onto the Adriatic promontory, Anatolian, Iranian and Oman ophiolites from late Lower Cretaceous to Palaeocene onto the Aegean, Anatolian and Arabic promontories. 相似文献
9.
10.
The Ardara pluton as part of the Donegal batholith was intruded into Neoproterozoic metasediments and metadolerites at mid-crustal
levels. The emplacement mechanism of the Ardara granite is very controversial, and mechanisms ranging from diapirism, ballooning
and stoping followed by nested diapirism have been proposed. Magnetic fabrics, rock fabrics and K/Ar dating of micas are used
here to constrain the emplacement history. The compositional zoning of the Ardara pluton is clearly reflected in the different
bulk magnetic susceptibilities between the outer quartz monzodiorite and the central granodiorite, whereas the intervening
tonalite is of intermediate nature. The magnetic carriers are characterized by the anisotropy of the magnetic susceptibility
(AMS), thermomagnetic measurements and through high field analyses (HFA). The separation of the ferrimagnetic and paramagnetic
contributions revealed that biotite and magnetite control the AMS in the quartz monzodiorite. Both minerals are oriented in
such a way that their summed contribution is constructive and originates from the shape fabric of magnetite and the texture
of biotite. Biotite is responsible mainly for the AMS in the tonalite and granodiorite. The magnetic foliation can be directly
related to the macroscopic foliation and also to the D4 structures in the country rocks. The foliation is consistent with
the geometry of the roughly circular shape and has a mostly steep to vertical dip. Towards the central granodiorite the magnetic
foliation dies out, although plagioclase texture measurements indicate a weak magmatic shape fabric. With the exception of
the tail, the Kmax axes (magnetic lineation) vary from steeply to gently plunging. The so-called lineation factor is approximately 1.01 and
therefore points to a less significant axial symmetry. These observations coincide with strain estimates on mafic enclaves
that show a very consistent pattern of K ∼0 flattening strain. Texture analyses of biotite and quartz additionally support
the observations made by the strain analyses and the magnetic fabric data. Microstructural investigations give evidence that
the fabrics are associated with the emplacement over a range of temperatures from truly magmatic to high-temperature solid-state
conditions. The age of the intrusion is still under discussion, but a new cooling age was determined by K/Ar dating of biotite
at 403.7±8 Ma corresponding to a temperature range between 450 and 300°C. For a mylonite along the southern contact between
the Ardara pluton and the country rock a K/Ar muscovite age of 378.8±7 Ma indicates a minimum age for the shear zone when
the Ardara pluton must have already been cooled down below 350±50°C.
Received: 28 January 1999 / Accepted: 28 December 1999 相似文献