Application of the QUILF thermobarometer to the peralkaline trachytes and pantellerites of the Eburru volcanic complex, East African Rift, Kenya   总被引：1，自引：0，他引：1  

Minghua Ren  Peter A. Omenda  Elizabeth Y. Anthony  John C. White  Ray Macdonald  D.K. Bailey   《Lithos》2006,91(1-4):109-124

The Quaternary Eburru volcanic complex in the south-central Kenya Rift consists of pantelleritic trachytes and pantellerites. The phenocryst assemblage in the trachytes is sanidine + fayalite + ferrohedenbergite + aenigmatite ± quartz ± ilmenite ± magnetite ± pyrrhotite ± pyrite. In the pantellerites, the assemblage is sanidine + quartz + ferrohedenbergite + fayalite + aenigmatite + ferrorichterite + pyrrhotite ± apatite, although fayalite, ferrohedenbergite and ilmenite are absent from more evolved rocks (e.g. with SiO₂ > 71%). QUILF temperature calculations for the trachytes range from 709 to 793 °C and for the pantellerites 668–708 °C, the latter temperatures being among the lowest recorded for peralkaline silicic magmas. The QUILF thermobarometer demonstrates that the Eburru magmas crystallized at relatively low oxidation states (ΔFMQ + 0.5 to − 1.6) for both trachytes and pantellerites. The trachytes and pantellerites evolved along separate liquid lines of descent, the trachytes possibly deriving from a more mafic parent by fractional crystallization and the pantellerites from extreme fractionation of comenditic magmas.  相似文献   

湿地生态系统碳循环过程及碳动态模型     

仝川  曾从盛 《福建地理》2006,(3)

从地上、地下有机物质生产对湿地碳输入的贡献,湿地土壤碳库以及土地利用变化对湿地土壤碳库和碳排放的影响,甲烷排放和可溶性有机碳输出以及影响因子,湿地生态系统碳循环动态模型4个方面对湿地生态系统碳循环国内外研究进展和研究成果进行综述、分析,提出了我国亚热带区域天然湿地碳循环研究的主要热点和方向:⑴沿海湿地碳库估算及土地利用转化对土壤碳库和温室气体排放的影响;⑵酸沉降对于我国东南沿海低纬度地区湿地甲烷排放的影响;⑶沿海湿地生态系统碳循环动态模型的应用与开发;⑷湿地系统可溶性有机碳的输出机理探讨.  相似文献   

Lake Sediment Core Records of Sulphur Accumulation and Sulphur Isotopic Composition in Central Ontario, Canada Lakes     

M. Catherine Eimers  Andrew M. Paterson  Peter J. Dillon  Sherry L. Schiff  Brian F. Cumming  Roland I. Hall 《Journal of Paleolimnology》2006,35(1):99-109

Stable isotopic compositions and concentrations of total sedimentary sulphur (S) were determined in cores from 6 lakes in the acid-sensitive Muskoka-Haliburton region of south-central Ontario. The isotopic composition of S in deep sediment (> ~ 20 cm) was approximately constant in all lakes, and indicated a pre-industrial δ ³⁴S value between +4.0 and +5.3‰, which is similar to current bulk deposition. Similarly, total S concentrations in deep sediment were relatively low (1.9–5 mg S g⁻¹ dwt) and approximately constant with depth within cores. All lakes exhibited up-core increases in total S and decreases in δ ³⁴S at a depth corresponding to the beginning of industrialization in the Great Lakes region ( ~ 1900), resulting in a generally reciprocal depth pattern between total S concentration and δ ³⁴S ratios. While initial shifts in total S and δ ³⁴S were likely due to enhanced SO₄ reduction of newly available anthropogenic SO₄, both the magnitude and pattern of up-core S enrichment and shifts in δ ³⁴S varied greatly among lakes, and did not match changes in S deposition post 1900. Differences between lakes in total S and δ ³⁴S were not related to any single hydrologic (e.g., residence time) or physical (e.g., catchment-area-to-lake area ratio) lake characteristic. This work indicates that sediment cores do not provide consistent records of changes in post-industrial S deposition in this region, likely due to redox-related mobility of S in upper sediment.  相似文献   

Modification of streaming potential by precipitation of calcite in a sand–water system: laboratory measurements in the pH range from 4 to 12     

Xavier Guichet  Laurence Jouniaux  Nicole Catel 《Geophysical Journal International》2006,166(1):445-460

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Shear wave splitting changes associated with the 2001 volcanic eruption on Mt Etna     

Francesca Bianco  Luciano Scarf&#;  Edoardo Del Pezzo  Domenico Patanè 《Geophysical Journal International》2006,167(2):959-967

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A study on the geochemical characteristics of Upper Permian continental marginal arc volcanic rocks in the northern segment of South Lancangjiang Belt     

沈上越冯庆来  魏启荣张志斌 张虎 《中国地球化学学报》2006,25(3):216-222

1IntroductionThe northern segment of the South LancangjiangBelt refers to the terrain about200km east of theYunxian-Lingcang granite in the South LancangjiangBelt(Fig.1).During the seventh Five-Year Plan peri-od,Mo Xuanxue et al.(1993)undertook the resear…  相似文献   

延边地区中生代火山岩的岩浆源区:来自Sr-Nd同位素和深源捕虏体(晶)的证据   总被引：6，自引：0，他引：6  

赵全国  许文良  靳克  裴福萍 《吉林大学学报(地球科学版)》2005,35(4):416-422

延边地区中侏罗世和早白垩世火山岩中包含有较多的辉石岩捕虏体和角闪石捕虏晶,前者为普通辉石变种,其化学成分类似于中国东部新生代玄武岩中单斜辉石巨晶的成分,具有岩浆堆积成因特征;后者为韭闪石和镁质绿钠闪石变种,其成分类似于中生代晚期玄武岩中角闪二辉石岩包体里的角闪石和新生代玄武岩中的角闪石巨晶.矿物温压计算结果显示,它们形成深度介于25～37km.延边地区中生代火山岩的(87Sr/86Sr)i值介于0.704 3～0.705 0,εNd(t)值介于2.33～4.71,表明岩浆源区应是一套具有亏损性质的新增生的地幔物质.综合上述结果,可以判定延边地区中生代火山岩的原始岩浆应来源于新增生的壳幔过渡带物质的部分熔融,地壳增生事件的时间为新元古代.  相似文献   

四川昌台农都柯金银矿矿床地质特征及成矿远景     

许远平  姚丽  李继军 《物探化探计算技术》2005,27(3):241-245

农都柯火山岩浅成低温热液型金银矿床系在三江地区义敦岛弧带被首次发现,经初步评价达到中型规模。矿床赋存于流纹质火山碎屑岩中,受北北西向剪切带控制,矿体呈透镜状或似层状,基本顺层产出。围岩蚀变强烈,以硅化为主,次为绢云母化和重晶石化。矿石由黄铁矿、闪锌矿、自然金、辉锑铅矿、砷黝铜矿、辉锑矿、辉锑银铅矿、雄黄、雌黄等组成,为典型的低温热液矿物组合。主矿化温度发生在200℃以下,矿化元素除Ag、Au外,As、Sb、Hg也达到或接近工业品位。通过地球物理、地球化学方法的测量,成矿远景较好。  相似文献   

伊宁吐拉苏火山盆地热液活动与金成矿关系     

漆树基  安其桂  伊发源 《新疆地质》2005,23(4):351-354

吐拉苏火山盆地中与金成矿有关的热液富含K^＋、Na^＋、F、SO4^2-和N2、O2等，是一种主要来源于岩浆．火山的热液，有大气水参于的次生热液．平均均一温度96～158℃，平均盐度0．26％～1．08％，热液活动深度0．26～0．67km，具有低温、低盐度、在地壳浅部活动的基本特征．热液活动生成围绕金矿体由内向外环状展布的黄英岩化、高级泥化、泥化和绿泥石碳酸盐化4个围岩蚀变带．与其有关的金成矿期分为原生沉积富集和次生热液交代蚀变2期，后者包括毒砂黄铁矿化、面状硅化、脉状硅化和绿泥石碳酸盐化4个成矿阶段．金富集成矿主要与黄英岩化蚀变带和面状硅化、脉状硅化2个成矿阶段密切相关．  相似文献   

岩石、土壤样品中210Po测定方法的研究   总被引：1，自引：0，他引：1  

王玉学 《铀矿地质》2005,21(4):248-256

研究了以铜箔为镀片时,自沉积总α计数法定量测定岩石、土壤样品中210Po的最佳制源环境、同位素的干扰和去除、共存元素的允许量以及适宜的溶(熔)矿方法,同时研究了银、铜两种镀片的区别。试验发现,当盐酸浓度为2.0mol/L,恒温80℃,振荡频率为180次/min、振程20mm时,制源2.0h,210Po自镀回收率在99.6%～100.4%之间,210Po加入量与α净计数率线性相关系数为0.9999。放置衰变法可以消除212Bi和218Po等短半衰期核素对210Po测量产生的影响,Vc存在时其它共存元素不干扰测定。方法配合HNO3HFHClO4溶矿(对复杂试样酸溶后的不溶渣,再进行碱熔),全程回收率为99.5%～100.4%。  相似文献