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101.
102.
Hydrous partial melting in the sheeted dike complex at fast spreading ridges: experimental and natural observations 总被引:5,自引:1,他引:4
Lydéric France Juergen Koepke Benoit Ildefonse Sarah B. Cichy Fabien Deschamps 《Contributions to Mineralogy and Petrology》2010,160(5):683-704
In ophiolites and in present-day oceanic crust formed at fast spreading ridges, oceanic plagiogranites are commonly observed
at, or close to the base of the sheeted dike complex. They can be produced either by differentiation of mafic melts, or by
hydrous partial melting of the hydrothermally altered sheeted dikes. In addition, the hydrothermally altered base of the sheeted
dike complex, which is often infiltrated by plagiogranitic veins, is usually recrystallized into granoblastic dikes that are
commonly interpreted as a result of prograde granulitic metamorphism. To test the anatectic origin of oceanic plagiogranites,
we performed melting experiments on a natural hydrothermally altered dike, under conditions that match those prevailing at
the base of the sheeted dike complex. All generated melts are water saturated, transitional between tholeiitic and calc-alkaline,
and match the compositions of oceanic plagiogranites observed close to the base of the sheeted dike complex. Newly crystallized
clinopyroxene and plagioclase have compositions that are characteristic of the same minerals in granoblastic dikes. Published
silicic melt compositions obtained in classical MORB fractionation experiments also broadly match the compositions of oceanic
plagiogranites; however, the compositions of the coexisting experimental minerals significantly deviate from those of the
granoblastic dikes. Our results demonstrate that hydrous partial melting is a likely common process in the root zone of the
sheeted dike complex, starting at temperatures exceeding 850°C. The newly formed melt can either crystallize to form oceanic
plagiogranites or may be recycled within the melt lens resulting in hybridized and contaminated MORB melts. It represents
the main MORB crustal contamination process. The residue after the partial melting event is represented by the granoblastic
dikes. Our results support a model with a dynamic melt lens that has the potential to trigger hydrous partial melting reactions
in the previously hydrothermally altered sheeted dikes. A new thermometer using the Al content of clinopyroxene is also elaborated. 相似文献
103.
Guillaume Dodet Bruno Castelle Gerd Masselink Timothy Scott Mark Davidson France Floc'h Derek Jackson Serge Suanez 《地球表面变化过程与地形》2019,44(1):393-401
The storm sequence of the 2013–14 winter left many beaches along the Atlantic coast of Europe in their most eroded state for decades. Understanding how beaches recover from such extreme events is essential for coastal managers, especially in light of potential regional increases in storminess due to climate change. Here we analyse a unique dataset of decadal beach morphological changes along the west coast of Europe to investigate the post-2013–14 winter recovery. We show that the recovery signature is site specific and multi-annual, with one studied beach fully recovered after 2 years, and the others only partially recovered after 4 years. During the recovery phase, winter waves primarily control the timescales of beach recovery, as energetic winter conditions stall the recovery process whereas moderate winter conditions accelerate it. This inter-annual variability is well correlated with climate indices. On exposed beaches, an equilibrium model showed significant skill in reproducing the post-storm recovery and thus can be used to investigate the recovery process in more detail. © 2018 John Wiley & Sons, Ltd. 相似文献
104.
YU Huimin XIA Qunke E.DELOULE YANG Xiaozhi CAS Key Laboratory of Crust-Mantle Materials Environments School of Earth Space Sciences University of Science Technology of Chin Hefei Anhui Chin CRPG-CNRS BP Vandoeuvre Cedex France 《《地质学报》英文版》2005,79(3):336-342
Hydrogen isotopic compositions of pyroxenes in peridotite xenohths from the Nushan volcano, Anhui Province, SE China have been obtained using an ion probe (Cameca 1270). D/H ratios are constant within a single grain and among the different grains from the same sample. The lack of correlation between the D/H ratios and the hydrogen contents indicates that the hydrogen isotopic compositions are inherited from their mantle source. Combining with the δD values of coexisting amphiboles, it is inferred that the Nushan mantle experienced at least a two-stage metasomatic event.One was responsible for formation of amphiboles with extremely variable δD values, and the other was probably responsible for the high δD values (up to -20‰) of some clinopyroxenes from peridotites, clinopyroxene and mica megacrysts. High δD values point to a subduction-related fluid being involved in one metasomatic event. The primary δD values (-90‰ to -140‰) of the Nushan pyroxenes, together with data gleaned from the literature, suggest that the D/H ratios of the nominally anhydrous mineral reservoir might have differed from that of the other mantle hydrogen in being relatively depleted in D. 相似文献
105.
PAN Junning WANG Hongchuan YAO Guoquan Graduate Student River Harbour Department Nanjing Hydraulic Research Institute Nanjing P. R. China.Engineer River Harbour Department Nanjing Hydraulic Research Institute Nanjing P. R. China. Professor River Harbour Department Nanjing Hydarulic Research Institute Nanjing P. R. China. 《中国海洋工程》1998,(2)
-In this paper a simple and efficient implicit finite-difference scheme is used for depth-averagedtwo-dimensional storm surge model.This finite-difference scheme is simpler and more efficient than the wi-dely-used ADI scheme.Accuracy analysis and stability analysis indicate that the scheme has two-order ac-curacy and is unconditionally stable when the grid size is constant.The present analysis results show thatthe scheme is of higher numerical accuracy than that introduced by Maa(1990).After tested by ideal mod-els,a calculation example of a real typhoon surge is carried out,the results of the numerical simulation co-incide well with the observed data and the accuracy is sufficient for engineering applications. 相似文献
106.
Yu Dingyong Xu Delun
Ph. D. Student Engineering College Ocean University of Qingdao Qingdao Professor Physical Oceanography Laboratory Ocean University of Qingdao Qingdao 《中国海洋工程》1997,(3)
The statistical distribution of wavelength is directly derived from a two-dimensional andspatially homogeneous Gaussian wave field.The present result differs from both the result of Rayleigh dis-tribution and Sun's result(1988b)which is transformed through the period distribution derived from atwo-dimensional and stationary Gaussian wave field.A laboratory experiment shows that the present re-sult is more consistent with the observations in the wave tank than the others. 相似文献
107.
本文对南秦岭大巴山区主要分布的早古生代地层各种岩石的含硒量的研究结果表明,含硒量与岩石的岩性和形成时代密切相关,与岩石的含碳量和含硫量成正线性关系。碳质板岩和石煤相对于其他类岩石的含硒量高,碳质板岩一般为6×10~(-6)~35×10~(-6),石煤的含硒量为8×10~(-6)~45×10~(-6);中、下寒武统和志留系大贵坪组的碳质板岩和石煤含硒量较高,可达30×10~(-6)。同时,下寒武统的含硒量远远大于早古生代其他层位同类岩石的平均含硒量,是同类岩石平均含量的5~10倍。如碳酸盐岩的含硒量为2×10~(-6)~4×10~(-6);细粒岩石的含硒量较粗粒岩石的含硒量高,下志留统陡山沟组的厚层状到中厚层状砂岩、粉砂岩和上寒武统的砾屑灰岩的含硒量相近,约0.05×10~(-6)~0.08×10~(-6),是本区最低的。因此,并非本区所有岩石都富硒。 相似文献