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201.
首先计算了欧亚地区均衡残差大地水准面.基于地幔热对流的内负荷理论和最新全球层析成像结果,探讨了欧亚地区中波长均衡残差大地水准面的地球动力学意义.研究结果表明,中波长均衡残差大地水准面主要受上地幔粘滞度和岩石层强度的影响,进而得出欧亚地区一些古老地盾和构造稳定地区的上地幔与年轻山脉及构造活动地区的上地幔结构存在着差异.这个差异主要是占老地盾和构造稳定地区,如波罗的海地盾、中西伯利亚地台、东欧等区域,冷却的上地幔已穿透地幔较深,上地幔与岩石层之间耦合较好;而年轻山脉和构造活动区,如帕米尔、天山、贝加尔活动带、青藏高原、日本海周围地区,在上地幔可能存在着热物质即粘滞度很低的软流层,上地幔与岩石层耦合程度较差,甚至有可能解耦.从欧亚地区上地幔属性的差异,可以解释该地区的一些地球动力学问题. 相似文献
202.
203.
南极罗斯岛及泰勒谷地区火山岩的地球化学特征及成因讨论 总被引:2,自引:0,他引:2
利用微量元素和Sr,Nd,Pb同位素资料,得出了南极罗斯岛及泰勒谷地区火山岩来自于上地幔,五个地区火山岩具有相同的源区。岩石具有大洋岛屿玄武岩(OIB)的特征。来自地幔的火山喷发的岩浆未遭受地壳物质的混染作用。地幔源区是具有高μ(=206Pb/204Pb)比值的地幔组分HIMU与亏损地幔组分DMM混合作用的结果,其中以HIMU组分为主,原生岩浆由具HIMU组分特征的深部地幔柱与浅部的DMM混合而成。 相似文献
204.
M. Selman Aydoan Hakan oban Mustafa Bozcu
mer Aknc 《Journal of Asian Earth Sciences》2008,33(3-4):155-176
The (late syn)- post-collisional magmatic activities of western and northwestern Anatolia are characterized by intrusion of a great number of granitoids. Amongst them, Baklan Granite, located in the southern part of the Muratdağı Region from the Menderes Massif (Banaz, Uşak), has peculiar chemical and isotopic characteristics. The Baklan rocks are made up by K-feldspar, plagioclase, quartz, biotite and hornblende, with accessory apatite, titanite and magnetite, and include mafic microgranular enclaves (MME). Chemically, the Baklan intrusion is of sub-alkaline character, belongs to the high-K, calc-alkaline series and displays features of I-type affinity. It is typically metaluminous to mildly peraluminous, and classified predominantly as granodiorite in composition. The spider and REE patterns show that the rocks are fractionated and have small negative Eu anomalies (Eu/Eu* = 0.62–0.86), with the depletion of Nb, Ti, P and, to a lesser extent, Ba and Sr. The pluton was dated by the K–Ar method on the whole-rock, yielded ages between 17.8 ± 0.7 and 19.4 ± 0.9 Ma (Early Miocene). The intrusion possesses primitive low initial 87Sr/86Sr ratios (0.70331–0.70452) and negative εNd(t) values (−5.0 to −5.6). The chemical contrast between evolved Baklan rocks (SiO2, 62–71 wt.%; Cr, 7–27 ppm; Ni, 5–11 ppm; Mg#, 45–51) and more primitive clinopyroxene-bearing monzonitic enclaves (SiO2, 54–59 wt.%; Cr, 20–310 ppm; Ni, 10–70 ppm; Mg#, 50–61) signifies that there is no co-genetic link between host granite and enclaves. The chemical and isotopic characteristics of the Baklan intrusion argue for an important role of a juvenile component, such as underplated mantle-derived basalt, in the generation of the granitoids. Crustal contamination has not contributed significantly to their origin. However, with respect to those of the Baklan intrusion, the generation of the (late syn)- post-collisional intrusions with higher Nd(t) values from the western Anatolia require a much higher amount of juvenil component in their source domains. 相似文献
205.
Megan Damon Masanori C. Kameyama Michael Knox David H. Porter Dave Yuen Erik O. D. Sevre 《Visual Geosciences》2008,13(1):49-57
The current availability of thousands of processors at many high performance computing centers has made it feasible to carry
out, in near real time, interactive visualization of 3D mantle convection temperature fields, using grid configurations having
10–100 million unknowns. We will describe the technical details involved in carrying out this endeavor, using the facilities
available at the Laboratory of Computational Science and Engineering (LCSE) at the University of Minnesota. These technical
details involve the modification of a parallel mantle convection program, ACuTEMan; the usage of client–server socket based
programs to transfer upwards of a terabyte of time series scientific model data using a local network; a rendering system
containing multiple nodes; a high resolution PowerWall display, and the interactive visualization software, DSCVR. We have
found that working in an interactive visualizastion mode allows for fast and efficient analysis of mantle convection results.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
206.
The geochemistry of mantle chromitites from the northern part of the Oman ophiolite: inferred parental melt compositions 总被引:2,自引:0,他引:2
Hugh Rollinson 《Contributions to Mineralogy and Petrology》2008,156(3):273-288
Chromitites from a single section through the mantle in the Oman ophiolite are of two different types. Low-cr# chromitites,
of MORB affinity are found in the upper part of the section, close to the Moho. High-cr# chromitites, with arc affinities
are found deeper in the mantle. Experimental data are used to recover the compositions of the melts parental to the chromitites
and show that the low-cr# chromitites were derived from melts with 14.5–15.4 wt% Al2O3, with 0.4 to 0.9 wt% TiO2 and with a maximum possible mg# of 0.76. In contrast the high-cr# chromitites were derived from melts with 11.8–12.9 wt%
Al2O3, 0.2–0.35 wt% TiO2 and a maximum melt mg# of 0.785. Comparison with the published compositions of lavas from the Oman ophiolite shows that the
low-cr# chromitites may be genetically related to the upper (Lasail, and Alley) pillow lava units and the high-cr# chromitites
the boninites of the upper pillow lava Alley Unit. The calculated TiO2–Al2O3 compositions of the parental chromitite magmas indicate that the high-cr# chromitites were derived from high-Ca boninitic
melts, produced by melting of depleted mantle peridotite. The low-cr# chromitites were derived from melts which were a mixture
of two end-members—one represented by a depleted mantle melt and the other represented by MORB. This mixing probably took
place as a result of melt–rock reaction.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
207.
在n维的Sr-Nd-Pb同位素空间中,几乎所有的大洋中脊玄武岩(MORB)和洋岛玄武岩(OIB)都落在一个虚拟平面上,被称为“地幔面(mantle plane)”。“地幔面”描述了大部分玄武岩的同位素地球化学特征,是最重要的、也是最早提出的地幔动力学演化特征之一,但是长期以来关于“地幔面”的内涵和意义并不清楚。本文通过一个综合模型,反演受岩浆作用控制的地幔微量元素(包括各种同位素母体元素)分异、Sr—Nd—Pb同位素演化,并推导出地幔Sr-Nd-Pb同位素演化的二元参数方程形式。模型表明,通过部分熔融向地壳输出相对富硅、富碱的物质成分,是地幔长期演化的主要特点,这个过程受到两个参数一部分融融程度(F)和岩浆分离的时间(t)-的控制,即n维参数可化为2维,因此在n维同位素空间出现“地幔面”的特征。壳源物资循环,能够使局部地幔偏离“地幔面”,就地幔总体统计特征而言,地壳混染的比例很低,不同的统计数据显示大约1%~6%的系统偏差,即可能的地壳混染程度;进一步模拟,可能作出更加精确的估算。 相似文献
208.
利用牡丹江(MDJ)和海拉尔(HIA)台1988-2000年的宽频带三分量数字地震记录,通过地幔间断面产生的P-SV转换波,研究台站下方地幔间断面的分布以及日本海俯冲带对660km间断面的影响.为了提高所得结果的可靠性,采用了线性-偏振滤波方法和修正的N次根倾斜叠加方法来提取P-SV转换波.前一方法通过实验选取适当的光滑平均和提出立体角的约束;对后一方法进行了震源深度校正和间断面倾斜的修正.结果表明,在MDJ和HIA台下方,除在660,410,220和520km深度附近均存有间断面外,在140,350,570,740和1080km深度附近也存在间断面,显示了地幔中径向分层的复杂性;另外,MDJ台下方660-840km之间的间断面结果比HIA台下方的复杂,似有分层结构,可能反映了俯冲带的影响. 相似文献
209.
通过求解全球能量平衡方程 ,得到地幔温度剖面。中地幔过渡带有一个温度突然增加 ,因此不能根据近地表数据向下做简单的外推。这个问题可以通过研究地球的冷却过程解决。目前地幔底部的温度值是 2 94 0K ,中地幔过渡带温度为 2 0 4 0K ,穿过这个带有一个 310K的突变。上部边界层底部的温度为 相似文献
210.