THE INTERRELATIONS BETWEEN COLLISIONAL AND TRAP MAGMATISM OF TAIMYR BASED ON GEOLOGICAL DATA AND MODELING RESULTS
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It is shown that in the Taymyr folded region the collision and trap magmatism are spatially combined. In time trap magmatism is associated with late-collision and post-collisional stages. Supercomputer modeling showed the possibility of mantle and crust heating in the late stages of collision, accompanied by basaltic magmatism in a quite large amount.Keywords:
Trap (plumbing)
Understanding the evolution of the mantle requires a knowledge of the relative variations of the major elements, trace elements and isotopes in the mantle. Most of the evidence for mantle heterogeneity is based on variations in the trace element and isotopic ratios of basaltic rocks. These ratios are presumed to reflect variations in the mantle sources. To compare major element heterogeneities with trace element and isotopic heterogeneities, it is necessary that the major element abundances in basalts also reflect variations in the mantle sources. Probably the only major element for which this is so is iron. If a basalt has only undergone fractional crystallization of olivine, then the abundance of FeO in the basalt reflects the FeO/MgO ratio of the mantle source, the degree of melting, and the pressure at which melting occurs. Relative pressures and degrees of melting can often be constrained, so that variations in the abundances of FeO can be used to obtain information about variations in the FeO/MgO ratio of the mantle sources of basalts. Comparison of FeO contents with trace element and isotopic contents of basalts shows some striking correlations and leads to the following conclusions. 1. Parental magmas for Kilauean basalts from Hawaii may be related by different degrees of melting of a homogeneous, garnet-bearing source. 2. Mid-ocean ridge basalts from the North Atlantic show a negative correlation of La/Sm with FeO, suggesting that the sources that are most enriched in incompatible trace elements are most depleted in FeO relative to MgO, and are probably also depleted in the other components of basalt. This correlation does not apply to the entire suboceanic mantle. 3. A comparison of tholeiites from near the Azores and from Hawaii shows that sources with similar Nd and Sr isotope ratios may have undergone distinctly different histories in the development of their major and trace element abundances. 4. Ocean island tholeiites tend to be more enriched in FeO than ocean floor tholeiites. Either the ocean island sources have greater FeO/MgO ratios, or melting begins at significantly greater pressures beneath ocean islands than beneath ocean ridges. 5. Major element variations in the mantle are controlled mainly by tectonics and the addition or removal of silicate melts. Trace element variations, however, may be controlled by the addition or removal of fluids as well. Thus major elements, trace elements and isotopes may each give a different perspective important to the understanding of the evolution of the mantle.
Trace element
Incompatible element
Fractional crystallization (geology)
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在北方 Qinling 早古生代的 granitoids 标明日期的锆石 U-Pb 产出 500， 452 和 420 妈的三座年龄山峰。他们能时间地被相关与对在 ca 的超离频压力的变态高压。500 妈，后退在 ca 的 granulite 外形变态。在 ca 的 450 妈和角闪岩外形变态。420 妈分别地。花岗石的 magmatism 的第一个事件被认为源于大陆人碰撞，而 magmatism 的第二和第三个事件被归因于外壳的高举。从高压、超离频压力的变形岩石与地区性的地质的背景和新结果结合了， ca。500 妈 magmatism 作为包括北方中国 Craton 的南部的边缘的在在南方 Qinling microcontinent 和北方 Qinling 带之间的 accretionary 楔的沉积岩石的部分融化的结果被解释。ca。450 妈集中的 magmatism 被归功于到脱水融化深深地以响应平板 breakoff 的变厚的条件的 subducted 大陆人外壳，和在 ca 的最后的 magmatism。420 妈作为到扩展的从收缩的在构造转变期间的部分融化的产品被解释。
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In this article, we study the possibility that Ceres has, or had in the past, a crust heavier than a pure or muddy ice mantle, in principle gravitationally unstable. Such a structure is not unusual in the Solar system: Callisto is an example. In this work, we test how the composition (i.e. the volumetric quantity of ice) and the size of the crust can affect its survival during thermo-physical evolution after differentiation. We have considered two different configurations: the first characterized by a dehydrated silicate core and a mantle made of pure ice, the second with a hydrated silicate core and a muddy mantle (ice with silicate impurities). In both cases, the crust is composed of a mixture of ice and silicates. These structures are constrained by a recent measurement of the mean density by Park et al. The Rayleigh–Taylor instability, which operates in such an unstable structure, could reverse all or part of the crust. The whole unstable crust (or part of it) can interact chemically with the underlying mantle and what is currently observed could be a partially/totally new crust. Our results suggest that, in the case of a pure ice mantle, the primordial crust has not survived until today, with a stability timespan always less than 3 Gyr. Conversely, in the case of a muddy mantle, with some 'favourable' conditions (low volumetric ice percentage in the crust and small crustal thickness), the primordial crust could be characterized by a stability timespan compatible with the lifetime of the Solar system.
Dwarf planet
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It is shown that in the Taymyr folded region the collision and trap magmatism are spatially combined. In time trap magmatism is associated with late-collision and post-collisional stages. Supercomputer modeling showed the possibility of mantle and crust heating in the late stages of collision, accompanied by basaltic magmatism in a quite large amount.
Trap (plumbing)
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Many geologists have been interested in the Okinawa Trough due to its unique tectonic environment.The magmatism is regarded as one of the key questions in the Okinawa Trough.The advances associated with the magmatism in the trough have been overviewed,including the studies about the characters of the magmatic sources,the processes of the magma melting and evolution and the regularities of melting.Based on these,the difficult questions on this field have been presented and a new idea that using the method of U-series disequilibria to study the magmatism in Okinawa Trough has been brought forward.Meanwhile,some research directions about the study of magmatism in the Okinawa Trough should be paid much attention to in the future,e.g.① the influence of the Philippine subduction slab on the magmatism processes,②the implications of the subducting sediment for the magma,③the controlling factors of the magma melting,④ the link between the magmatism and the seafloor hydrothermal activity.
Trough (economics)
Seafloor Spreading
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New ReOs isotopic results for Os-poor basalts from St. Helena, the Comores, Samoa, Pitcairn and Kerguelen dramatically expand the known range of initial 186Os/187Os ratios in OIBs to values as high as 1.7. In contrast to the Os isotopic uniformity of Os-rich basalts from the HIMU islands of Tubuai and Mangaia found by Hauri and Hart [1], our values for St. Helena span most of the known range of Os isotopic variability in oceanic basalts (initial 187Os/186Os ranges from 1.2 to 1.7). Generation of such radiogenic Os in the mantle requires melting of source materials that contain large proportions of recycled oceanic crust. The very low Os concentrations of most of the basalts analyzed here, however, leave them susceptible to modification via interaction with materials containing radiogenic Os in the near-surface environment. Thus the high 186Os/187Os ratios may result from assimilation of radiogenic Os-rich marine sediments, such as Mn oxides, within the volcanic piles traversed by these magmas en route to the surface. Furthermore, the Os isotopic signatures of Os-rich, olivine-laden OIBs may reflect the accumulation of lithospheric olivine, rather than simply their mantle source characteristics. The extent to which these processes alter the view of the mantle obtained via study of ReOs systematics in oceanic basalts is uncertain. These effects must be quantified before ReOs systematics in OIBs can be used with confidence to investigate the nature of mantle heterogeneity and its causes.
Radiogenic nuclide
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Noble gas
Isotopic signature
Hotspot (geology)
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