天山冰川消融参数化能量平衡模型   总被引：34，自引：0，他引：34  

康尔泗 Ohmur  A 《地理学报》1994,49(5):467-476

本文运用在天山乌鲁木齐河源的冰川能量平衡观测和常规气象站观测要素，建立了冰川消融参数化能量平衡模型。以日照、日平均气温、低云量、水汽压和风速为模型基本输入因子，模拟计算和讨论了消融期冰川表面辐射平衡和能量平衡。  相似文献   

黑龙江省尚志地区新生代钾质玄武岩研究     

刘贤华 《岩石学报》1990,6(3):53-64

尚志中新世富碱的钾质系列玄武岩为白榴霞石岩、橄榄霞石岩、霞石碧玄岩和橄榄碧玄岩。岩石中似长石矿物大量出现,霞石和白榴石可以共存。稀土元素和大离子不相容元素的特征表明形成白榴霞石岩、橄榄霞石岩、霞石岩碧玄岩和橄榄碧玄岩的地幔熔融程度越来越高。主元素和微量元素的模拟计算表明,霞石岩岩浆为上地幔岩2～4％的熔融,碧玄岩为上地幔橄榄岩5～8％的部分熔融;这些岩浆形成时的温压条件为:霞石岩的T=1410～1430℃,P=22～23×10~8Pa;碧玄岩的T=1380～1430℃,P=20～23.5×10~8Pa。  相似文献   

中国晚新生代火山和现代高温水热系统   总被引：7，自引：0，他引：7  

佟伟  穆治国 《地球物理学报》1990,33(3):329-335

中国的晚新生代火山并不罕见,它们主要分布在东北-华北、东南沿海、台湾北端以及昆仑山区和云南省腾冲县境内.前二区为大陆板内火山,以喷出碱性系列为主.台湾北端是中国唯一的酸性火山岩区.昆仑山和腾冲火山则为陆-陆碰撞型板缘火山,以喷出钙碱系列为主,但昆仑山区以南既有碱钙系列,又有碱性系列.五大连池和白头山等板内火山虽然年青附近却不存在高温水热活动;西藏南部存在板缘高温水热活动,却没有任何近代火山.这一现象表明,地表火山未必是西藏地下存在高温水热资源的必要条件,壳内局部熔融也许是藏南高温水热活动的可几热背景.  相似文献   

邓阜仙花岗岩熔融实验研究   总被引：9，自引：0，他引：9       下载免费PDF全文

宋新华  周珣若  吴国忠 《地质科学》1988,(3):247-258

本文通过对邓阜仙花岗岩饱和水熔融实验结果的计算处理和岩石学相图的分析,从实验岩石学的角度证实了邓阜仙花岗岩是岩浆结晶的,而不是花岗岩化形成的。同时,由实验表明,岩石初熔温度除与岩石成分有关外,还与岩石实际形成条件有密切联系。此外,在加氟化物的饱和水熔融实验中,氟化物不仅能降低岩石初熔温度,而且改变了岩浆体系中不同矿物的稳定性,主要使云母和石英变得稳定,酸性斜长石变得不稳定,而钾长石的稳定性基本不变。  相似文献   

Petrological investigation of the Ganyu peridotite in the Sulu ultrahigh-pressure terrane, eastern China   总被引：1，自引：0，他引：1  

Shizhong Chen  Jingsui Yang 《Tectonophysics》2009,475(2):383-203

The ultramafic body sampled in the Chinese Continental Scientific Drilling (CCSD) Hole PP3 is located in the eastern part of the Dabie-Sulu UHP metamorphic belt near Donghai County. It is about 480 m thick, and consists chiefly of garnet peridotite, dunite and serpentinite. The principal minerals include olivine, chromium spinel, diopside, enstatite, garnet with minor secondary augite, phlogopite and amphibole. Both the olivine and orthopyroxene are highly magnesian, and the garnet is pyropic with 5.4-6.4% CaO and 0.3-3.3% Cr₂O₃. Two generations of clinopyroxene are present; an early diopside followed by augite. Chromium spinels are highly variable with Cr#s (100Cr / (Cr + Al)) between 51 and 89, and their compositions reflect different processes of formation, namely partial melting and eclogite, amphibole and greenschist facies metamorphism. The Mg#s (100 Mg / (Mg + Fe²⁺))of the spinels correlate positively with the Cr#s but negatively with oxygen fugacity. Based on the spinel compositions the ultramafic rocks originated in the shallow mantle, then subducted to depths of more than 100 km and finally exhumed to the surface. They underwent partial melting at shallow depths, mostly in the spinel facies, and were later transformed into garnet peridotites during deep subduction. All of the rocks were weakly metasomatized during exhumation and were subjected to retrograde metamorphism.  相似文献   

The formation of foliated (garnet-bearing) granites in the Tongbai-Dabie orogenic belt: partial melting of subducted continental crust during exhumation   总被引：3，自引：0，他引：3  

L. ZHANG  Z. ZHONG  H. ZHANG  W. SUN  H. XIANG 《Journal of Metamorphic Geology》2009,27(9):789-803

Foliated (garnet-bearing) (FGB) granites are associated closely with and are usually the major wall rocks of the high-pressure (HP) and ultrahigh-pressure (UHP) metamorphic rocks in the Tongbai-Dabie region, the mid segment of the Qinling-Dabie-Sulu orogenic belt in central China. These granites appear either as small plutons or as veins, which commonly intrude into or surround the HP and UHP metamorphic eclogites or gneisses. The veins of FGB granites usually penetrate into the retrograded eclogites or gneisses along the foliations. Condensation rims can occasionally be found along the margins of granite veins. These granites are rich in Si and alkali with high Ga/Al ratios, and depleted in Ca, Mg, Al, Ti, Sc, V, Ni, Co, Cr and Sr, which are similar to A-type granites. In a chondrite normalized diagram, the samples are light rare earth elements enriched with different extent of negative Eu anomaly. Moreover, Rb, Nb, Ta, Sr, P and Ti show different degrees of negative anomalies, whereas Ba, K, La, Zr and Hf show positive anomalies in the primitive mantle normalized diagram. Negative anomalies of Eu and Sr indicate strong influence of plagioclase. In conventional discrimination diagrams, these FGB granites belong to the A-type granite, with geochemical characteristics affinitive to post-collisional granites. The εNd (230 Ma) values (−15.80 to −2.52) and T _DM values (1.02–2.07 Ga) suggest that magma for the FGB granites were derived from a heterogeneous crustal source. Therefore, the FGB granites may provide clues for deciphering the formation of post-collisional granites. It is proposed that the magma of the FGB granites both in the HP and UHP units was formed in an extensional tectonic setting slightly post-dating the HP and UHP metamorphism, most likely as a result of decompressional partial melting of UHP retrograded eclogites during exhumation.  相似文献   

Thermocalc and experimental modelling of melting of pelite, Morton Pass, Wyoming   总被引：1，自引：0，他引：1  

J. A. GRANT 《Journal of Metamorphic Geology》2009,27(8):571-578

Calculated results using thermocalc for melting of pelitic compositions are compared with the results of experimental melting of pelite from Morton Pass, Wyoming, USA. The experiments were carried out at 1, 2 and 3.5 kbar, dominantly at 2 kbar. For experimental charges with ('wet') and without ('dry') added H₂O, the agreement is good. This is true for the compositions without added H₂O, in which liquid first appears with the production of orthopyroxene at ∼800 °C, and for the runs with added H₂O, in which melting begins at ∼700 °C, and continues, with the appearance of orthopyroxene between 780 and 800 °C at 2 kbar. The compositions of melts are also compared: the comparison is generally good, except in the modelling of wet runs below ∼780 °C, where the calculated values for FeO and MgO are about one-tenth of the already low analytical values, and in somewhat low calculated values of Al₂O₃ compared to the analytical data. A quantitative model to illustrate melting of pelite at Morton Pass is calculated, giving T – X (H₂O) conditions for the observed sets of natural assemblages, along with the reactions at and near the beginning of melting.  相似文献   

藏东南超镁铁质岩墙及其地质意义   总被引：1，自引：1，他引：0       下载免费PDF全文

徐晓霞  丁林  许强  蔡福龙  张清海  张利云  来庆洲 《地质科学》2009,44(3):1012-1024

青藏高原东南部出露有大量近东西向展布的(超)镁铁质岩墙,锆石U?Pb年龄聚集在145～130 Ma之间。矿物学及岩石学结果显示：哲古错地区的亚碱性超镁铁苦橄质岩石源于150～180 km深处, 5～6 GPa下石榴石二辉橄榄岩地幔高比率的部分熔融; 碱性超镁铁质岩石源于石榴石-尖晶石二辉橄榄岩转换带,是低比率部分熔融的产物; 镁铁质岩石的岩浆在演化过程中遭受了低压下结晶分离作用的改造,不能代表原始岩浆的成份。藏东南(超)镁铁质岩石是不同深度地幔物质不同比率部分熔融的产物,亚碱性超镁铁苦橄质岩墙的出现指示了晚侏罗-早白垩印度板块北缘存在的高比率部分熔融的岩浆活动事件,暗示了地幔柱的存在和影响。  相似文献   

新疆东天山大黑山地区眼球状花岗片麻岩成因及形成环境          下载免费PDF全文

余吉远  孟勇  郭琳  李建星  白定邦 《地质找矿论丛》2009,24(4):335-340

文章对东天山大黑山地区眼球状花岗质片麻岩的特征及其成因进行探讨。通过野外地质调查和岩石学、矿物学、地球化学的研究,认为区内岩体为岛弧钙碱性火山-沉积岩系原地重熔改造的产物,这种原地花岗片麻岩的成岩过程主要为深源熔体和流体与原岩的相互作用,使原岩发生不同程度的部分熔融,因而其地球化学特征同时受到原岩和外来熔体-流体的控制。锆石U-Pb年龄为1 141 Ma,代表了重熔事件的时间。根据岩石地球化学及构造环境判别图解认为该岩体为碰撞造山后期-期后的产物。  相似文献   

内蒙古天和永新生代玄武岩成因及其地质意义   总被引：1，自引：0，他引：1       下载免费PDF全文

杨宗锋  罗照华  张华锋  章永梅  黄凡  孙晨光  戴紧根 《地学前缘》2009,16(2):90

天和永玄武岩为碧玄岩,至少可以划分出3种矿物共生组合类型。天和永玄武岩总体具有贫硅(w(SiO2)=43.97%～45.68%)、富碱(w(K2O+Na2O)=5.91%～7.65%)、富钾(w(K2O)=2.04%～2.89%)、高钛(w(TiO2)=2.18%～2.37%)、高Mg值(Mg#=68～76)的特征;稀土元素含量高(∑REE=(246.62～329.82)×10-6),稀土配分曲线呈右倾平滑直线,强烈富集轻稀土,轻重稀土强烈分馏((La/Yb)N>30),无明显的Eu(δEu=0.90～1.02)和Ce异常(δCe=0.96～1.00);强烈富集不相容元素,其中高场强元素(HFSE)Nb、Ta和Th出现峰值,具有近似OIB配分型式的特征;玄武岩富含相容元素Co((39.1～48.9)×10-6)、Ni((130～257)×10-6)、Cr((138～320)×10-6)。上述所有特征以及岩石结晶程度低、富含橄榄岩包体和少量捕虏晶、元素变异关系等均表明,天和永玄武岩是原生玄武岩质岩浆固结的产物。微量元素比值Ba/Rb(12～35)和碱金属的变化暗示源区可能遭受过流体的交代作用,源岩可能是富集的二辉橄榄岩。岩石成因模拟表明,形成天和永玄武岩的原生岩浆是在变压、部分熔融的条件下富集地幔源区岩石非实比熔融的产物,变压熔融柱穿切了Sp/Gt二辉橄榄岩相边界。岩浆形成于源区岩石的低度(约<5%)部分熔融,其中石榴石二辉橄榄岩部分熔融约为1%,尖晶石二辉橄榄岩部分熔融2%～5%。综合分析显示,源区部分熔融的触发机制是边际驱动的地幔对流,因而其形成深度大于东部的集宁玄武岩和汉诺坝玄武岩。  相似文献