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1.
湖南新宁金家锑矿床是湘中地区较具有经济价值的锑矿床。文章通过矿石稀土元素、微量元素、铅同位素分析以及流体包裹体岩相学观察、均一法测温和包裹体气液相成分分析,研究了金家锑矿床成矿流体的性质及演化。研究表明:①矿石中稀土元素总量w(ΣREE)=151.21×10-6～212.41×10-6,平均180.52×10-6;LREE/HREE=15.21～18.54,轻稀土富集,具中等负铕异常;矿石微量元素蛛网图表明,富集Rb,U,Th等大离子亲石元素(LILE),而亏损Nb,Ta,Ti等高场强元素;铅同位素组成206 Pb/204 Pb=18.032～18.391,207 Pb/204 Pb=15.403～15.495,208Pb/204Pb=38.025～38.215,表明成矿物质来自深源;②流体包裹体主要为气液两相包裹体,液相成分阳离子以K+,Na+,Ca2+,Mg2+为主,阴离子以SO24-,Cl-,F-为主;气相成分以H2O,CO2,CH4为主。包裹体均一温度100～240℃,主要为140～200℃,盐度2.60%～3.80%,表明金家锑矿床为典型的中低温热液矿床,其成矿流体为中-低温、低盐度热液。 相似文献
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通过对双朋西金铜矿床流体包裹体岩相学、测温学及铅、硫同位素等的分析,研究其成矿流体性质和演化,并探讨矿床成矿流体来源,结果表明:①流体包裹体主要为气液两相包裹体;包裹体液相成分阳离子以Na+、K+、Ca2+为主,阴离子主要以SO2-4、Cl-为主;气相以H,2O、CO2为主.②双朋西金铜矿床成矿流体为中高温、中等盐度、中等密度、中等压力的流体.③铅同位素206Pb/204Pb为18.058～18.710,207Pb/204Pb为15.581～15.641,208Pb/204Ph为38.191～38.531;δ34S值(‰)变化范围为+3.1～+6.2,平均值为+4.42;综合分析认为,本区铅、硫同位素来源应为壳幔混合源. 相似文献
3.
《矿产与地质》2020,(1)
大别山北麓地质构造复杂,岩浆活动强烈,桐-商深大断裂对萤石矿控矿作用显著,燕山期中酸性花岗岩与区内萤石矿关系密切。萤石流体包裹体中δ18 O变化范围为1.14‰～13.78‰、!D为-110.8‰～-68.4‰;共伴生黄铁矿、方铅矿,!34S/!32S比值变化范围为-19.271‰～1.707‰,206Pb/204Pb比值为16.655～16.850、207Pb/204Pb比值为15.324～15.398、208Pb/204 Pb比值为37.514～37.993;流体包裹体均一温度均值为133℃,盐度w(NaCleq)平均值为4.70%,密度平均值为0.97g/cm3。综合研究认为:氢、氧同位素显示萤石中成矿流体为岩浆水、变质水为主,大气降水参与的混合成矿热液;硫同位素显示硫源较复杂,铅同位素显示铅源主要来自下地壳重熔岩浆及部分上地幔的铅混入;成矿流体主要为低温低盐度、较低密度的热液流体,矿床类型多属于热液充填型萤石矿床。 相似文献
4.
甘肃阳坝铜多金属矿床流体包裹体及S、Pb同位素组成特征 总被引：1，自引：1，他引：0
甘肃省阳坝铜多金属矿床位于碧口地体的东北部,矿体呈层状、似层状赋存于碧口群阳坝组细碧凝灰岩和凝灰质千枚岩的过渡部位,根据矿床地质特征,将成矿期划分为海底火山喷流沉积期和变质热液叠加改造期。基于对阳坝矿床详细的野外观察和矿相学的研究,通过对矿床流体包裹体和S、Pb同位素的研究,总结矿床的成矿流体性质和成矿物质来源,探讨成矿机制。研究表明,阳坝矿床海底火山喷流沉积期流体包裹体类型主要为水溶液包裹体,成矿流体均一温度为135～336℃,盐度w(NaCl_(eq))为0.70%～10.61%,密度为0.58～0.97g/cm~3;包裹体气相成分以H_2O为主,含少量的CO_2和N_2,属于中低温、低盐度的H_2O-NaCl流体体系,与典型VMS型矿床成矿流体特征相似;变质热液叠加改造期流体包裹体类型主要为水溶液包裹体、CO_2-H_2O包裹体和纯CO_2包裹体,成矿流体均一温度为179～384℃,盐度w(NaCl_(eq))为3.39%～14.78%,密度为0.61～0.99 g/cm~3,包裹体气相成分富含CO_2及少量N_2,属于中高温、低盐度的H_2O-CO_2-NaCl±N_2流体体系,与区域上造山型金矿成矿流体特征一致,均为来自深部的变质流体。喷流沉积期矿石硫化物的δ~(34)S为-7.5‰～3.4‰,均值为-0.46‰,成矿热液δ~(34)S_(∑S)值≈3.73‰,变质热液叠加改造期硫化物的δ~(34)S为-6.7‰～3.3‰,均值-0.575‰,均显示幔源硫的特征。喷流沉积期(~(206)Pb/~(204)Pb=17.505～18.008、~(207)Pb/~(204)Pb=15.521～15.558、~(208)Pb/~(204)Pb=37.494～37.851)与变质热液叠加改造期(~(206)Pb/~(204)Pb=17.293～17.947、~(207)Pb/~(204)Pb=15.498～15.542、~(208)Pb/~(204)Pb=37.388～37.640)的矿石硫化物的Pb同位素组成相近,认为2期矿石铅具有相同来源。通过与阳坝组火山岩、阳坝岩体的Pb同位素组成对比,并结合Pb同位素源区特征值、构造模式图解和△β-△γ成因分类图解分析,认为矿石铅来自上地壳和地幔的混合。阳坝铜多金属矿床属于海底火山喷流沉积-变质热液叠加改造型矿床。 相似文献
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甘肃合作早子沟金矿床流体包裹体及硫铅同位素特征 总被引：1，自引：0，他引：1
早子沟金矿床是西秦岭西段近年来发现的大型金矿床之一。矿床产于中三叠世古浪堤组中,矿体产出与中酸性岩脉关系密切;矿体受断裂控制,呈脉状、条带状,少数似层状产出。含金石英脉可分为两个成矿期次,分别为含金粗粒石英脉期和多金属硫化物-金石英期;金属硫化物主要为辉锑矿、黄铁矿、毒砂等。辉锑矿石英脉型金矿石中流体包裹体主要为富液相的气液两相流体包裹体,均一温度为129.8 ~324.3 ℃,平均为203.2 ℃,盐度（w（NaCl））为1.22%~10.73%,平均为6.04%,成矿流体的密度平均为0.90 g/cm3,矿床的成矿平均深度约为2.00 km;阴阳离子分析结果表明,流体包裹体液相成分主要为Na+-SO42--Cl-,单个流体包裹体激光拉曼显示流体包裹体中的气相成分主要为H2O、CO2和SO2,个别样品显示有CO和CH4,成矿流体为NaCl-H2O-CO2体系。流体包裹体研究揭示了早子沟金矿床辉锑矿-金成矿阶段的成矿流体为浅成中低温低盐度低密度流体,主要为岩浆水与地下水的混合热液,不同性质流体的混合作用和它们的沸腾作用是使金沉淀的重要因素。矿石中辉锑矿硫同位素组成很稳定,δ34SV-CDT值为-10.30‰~-8.10‰,平均为-9.33‰,表明硫主要为岩浆热液来源,并混有地层硫。矿石铅同位素组成显示206Pb/204Pb为18.166~19.027,207Pb/204Pb为15.608~15.741,208Pb/204Pb为38.249~39.275,矿石铅同位素组成为壳幔混合成因铅。根据早子沟金矿床特征,结合成矿流体性质及来源、成矿物质来源研究成果,推测甘肃早子沟金矿床应为岩浆期后低温热液金矿床。 相似文献
6.
广西大厂矿田主要由锡多金属矿床和拉么矽卡岩型锌铜矿床组成,前者产于远离龙箱盖岩体的泥盆系中,而后者产于龙箱盖岩体内外接触带。过去多认为两者属于同一成矿系统,都与龙箱盖岩体有关。本文分析和总结了这两类矿床的成矿流体地球化学特征及硫化物原位铅同位素组成,探讨这两类元素组合不同的矿床是否属于同一成矿系统。锡多金属矿床主要发育含CO2包裹体、水溶液包裹体和少量含石盐子晶包裹体,而拉么矽卡岩型锌铜矿床主要发育水溶液包裹体,表明锡多金属矿化流体比矽卡岩型锌铜矿化流体含有更多CO2。锡多金属矿床流体包裹体的均一温度集中于270～410℃,而拉么矽卡岩型锌铜矿床流体包裹体的均一温度集中在240～325℃。远离岩体的锡多金属矿床矿化温度高于靠近岩体的矽卡岩型铜锌矿床矿化温度,这与同一岩浆成矿系统热液矿床的成矿温度一般从岩体往外逐渐降低不同。100号锡多金属矿床硫化物原位铅同位素组成为:208Pb/204Pb介于38.790～39.048之间、207Pb/204Pb介于15.677～15.752之间和206Pb/204Pb介于18.569～18.691之间。拉么矽卡岩型锌铜矿床硫化物的208Pb/204Pb、207Pb/204Pb和206Pb/204Pb分别为38.731～39.112、15.668～15.762和18.411～18.607。两类矿化铅同位素组成在207Pb/204Pb-206Pb/204Pb和208Pb/204Pb-206Pb/204Pb图解上位于不同的区域,表明两类矿化成矿物质源区不同。两类不同矿床成矿流体CO2含量、He及B同位素组成也不同,其矿化流体来源有一定的差异。此外,龙箱盖岩体黑云母富锡,表明岩浆中的Sn主要为Sn4+置换黑云母中的Ti4+,不利于Sn在残余岩浆中富集成矿。上述差异表明大厂矿田锡多金属矿床和矽卡岩型锌铜矿床不是同一岩浆-热液成矿系统的产物,拉么矽卡岩型锌铜矿床和龙箱盖岩体有关,锡多金属矿床可能和深部未出露岩体有关。 相似文献
7.
湘西—黔东下寒武统铅锌矿床流体包裹体和硫、铅、碳同位素地球化学特征 总被引：5，自引：0，他引：5
湘西—黔东下寒武统铅锌矿床位于湘西—鄂西成矿带西南部湘黔边境地区,是一类产于寒武系清虚洞组藻灰岩中的铅锌矿床。对李梅、狮子山、嗅脑、卜口场4个矿床开展了流体包裹体及硫、铅、碳同位素地球化学分析,分析结果表明:铅锌矿石流体包裹体具有低温、中-高盐度特点;硫化物δ34S值较高;围岩及方解石的δ13C、δ18O组成均为正常海相碳酸盐的碳、氧同位素组成;矿石与围岩的铅同位素组成变化范围不大,所有铅同位素数据在207Pb/204Pb-206Pb/204Pb图中呈线性分布。综合分析认为,湘西—黔东下寒武统铅锌矿床成矿流体可能为区域迁移流体与地层封存水构成的混合流体,成矿物质大部分来源于碳酸盐岩围岩地层,可能有部分Pb、Zn等金属元素随区域迁移流体带入,矿床的形成可能为两种来源流体混合后Pb、Zn等金属元素因物理化学条件的改变而沉淀成矿,矿床成因类型应为密西西比型铅锌矿床。 相似文献
8.
通过对双朋西金铜矿床流体包裹体岩相学、测温学及矿石铅、硫同位素等的分析,研究成矿流体性质和演化、成矿流体来源。结果表明:流体包裹体主要为气液两相包裹体,另有少量液相和含子矿物包裹体。包裹体液相成分阳离子以Na+,K+,Ca2+为主,阴离子主要以SO42-,Cl-为主;气相以H2O,CO2为主。均一温度范围为210~370℃和370~460℃,盐度3.0%~6.5%,密度集中于0.600~0.800 g/cm3,压力主要为8.0~20.0 MPa,为中高温、中等盐度、中等密度、中等压力的成矿流体。铅同位素206Pb/204Pb为18.058~18.710,207Pb/204Pb为15.581~15.641,208Pb/204Pb为38.191~38.531,δ(34S)为+3.1×10-3~+6.2×10-3,平均值为+4.42×10-3,成矿流体铅、硫同位素来源为壳幔混合源。 相似文献
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比利亚谷银铅锌多金属矿床位于大兴安岭西坡的得尔布干成矿带,它是近些年来在该区新发现的一座大型银铅锌多金属矿床。该矿床矿体主要呈脉状、细脉浸染状、角砾状赋存于塔木兰沟组中—基性火山岩和满克头鄂博组酸性火山岩中的NW向断裂体系内。根据矿石的结构、构造以及矿物之间的共生组合、穿切关系,将成矿过程从早到晚划分为硅化石英+黄铁矿阶段（Ⅰ）、石英+黄铁矿+闪锌矿阶段（Ⅱ）、石英+黄铁矿+闪锌矿+方铅矿+辉银矿+黄铜矿±黝铜矿阶段（Ⅲ）、石英+黄铁矿+方解石+萤石±蛋白石阶段（Ⅳ）;详细的石英、闪锌矿流体包裹体研究揭示：成矿早阶段（Ⅰ、Ⅱ）石英中发育WL型、C型包裹体,包裹体完全均一温度为188~254℃,盐度（w（NaCl））为1.83%~4.79%,密度为0.81~0.94 g/cm3,属于中低温、低盐度的H2O-NaCl-CO2体系;成矿主阶段（Ⅲ）石英、闪锌矿中发育WL型包裹体,包裹体完全均一温度为160~188℃,盐度为3.69%~7.15%,密度为0.92~0.96 g/cm3,属于低温、中低盐度的H2O-NaCl-CH4体系;成矿晚阶段（Ⅳ）石英中发育WL型、L型包裹体,WL型包裹体完全均一温度为130~165℃,盐度为1.22%~3.53%,密度为0.93~0.95 g/cm3,属于低温、低盐度的H2O-NaCl体系。流体包裹体H-O同位素地球化学特征揭示：早阶段流体的δ18OH2O-SMOW值为-6.3‰~-5.9‰,δDH2O-SMOW值为-163.4‰~-162.7‰;成矿主阶段流体的δ18OH2O-SMOW值为-14.4‰,δDH2O-SMOW值为-165.4‰~-162.0‰;成矿晚阶段流体的δ18OH2O-SMOW值为-19.1‰,δDH2O-SMOW值为-150.7‰;硫化物Pb同位素比值分别为206Pb/204Pb=18.435~18.513、207Pb/204Pb=15.579~15.675、208Pb/204Pb=38.283~38.603。这种特征揭示,该矿床成矿流体为低温、低盐度的H2O-NaCl-CH4体系,早期为残余岩浆水和大气降水混合、中—晚期大气降水逐渐增加;成矿物质源于壳幔混合源区;成矿过程以流体混合方式导致成矿元素聚集和沉淀,矿床成因类型为与陆相火山-次火山作用有关的低硫化型浅成热液铜（银）铅锌多金属矿床;其整体与大兴安岭西坡同类型矿床相似,成矿作用发生在早白垩世（131.3 Ma）,与古太平洋板块俯冲产生的弧后伸展环境相关。 相似文献
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1017高地银多金属矿床位于内蒙古自治区东乌珠穆沁旗,矿区大地构造位置处于西伯利亚板块东南缘查干敖包-奥尤特-朝不楞早古生代构造-岩浆岩带东段。石英脉型矿石中流体包裹体研究显示,从成矿早期到主成矿期,流体温度逐渐降低(从404℃~134℃到236℃~121℃),盐度都为中低盐度,由此表明该矿床具有浅成、中低温、中低盐度热液成矿特征。激光拉曼光谱分析显示包裹体气液相成分主要为H2O。矿石硫同位素组成相对均一,δ34S介于3.4‰~8.0‰之间,均值5.35‰,与幔源S的δ34S值(介于-3‰~3.0‰之间)比较,有向沉积硫的明显漂移,表明矿石中硫来源于沉积硫与岩浆硫的混合、平衡作用;矿石硫化物铅同位素比值没有明显的差别,206Pb/204Pb值为18.274 0~18.399 6,207Pb/204Pb值为15.539 9~15.561 6,208Pb/204Pb值为38.036 3~38.177 2,具有钍铅微弱亏损特征,指示矿石中硫化物的铅源主要来自地壳深部的岩浆源区,伴随岩浆及其热液作用,不可避免地混入了部分富放射成因铅的地壳物质。矿石氢氧同位素组成为:δDV-SMOW值介于-103‰~-125‰之间,δ18 OV-SMOW值在6.9‰~13.9‰之间,显示成矿流体中的水来源于岩浆水与大气降水的混合。综合1017高地银多金属矿床的地质特征和流体包裹体、S,Pb,H,O同位素研究认为,该矿床成矿物质来源于深源岩浆和上地壳的混合,成矿流体主要来自岩浆期后热液和大气降水,其成因类型可归于中低温度、中低盐度的岩浆期后热液型银多金属矿床。 相似文献
11.
S. Viswanathan K. Surya Prakash Rao B. Mahabaleswar 《Journal of the Geological Society of India》2013,82(6):621-627
Komatiites are mantle-derived ultramafic volcanic rocks. Komatiites have been discovered in several States of India, notably in Karnataka. Studies on the distribution of trace-elements in the komatiites of India are very few. This paper proposes a simple, accurate, precise, rapid, and non-destructive wavelength-dispersive x-ray fluorescence (WDXRF) spectrometric technique for determining Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th in komatiites, and discusses the accuracy, precision, limits of detection, x-ray spectral-line interferences, inter-element effects, speed, advantages, and limitations of the technique. The accuracy of the technique is excellent (within 3%) for Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Zr, Nb, Ba, Pb, and Th and very good (within 4%) for Y. The precision is also excellent (within 3%) for Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th. The limits of detection are: 1 ppm for Sc and V; 2 ppm for Cr, Co, and Ni; 3 ppm for Cu, Zn, Rb, and Sr; 4 ppm for Y and Zr; 6 ppm for Nb; 10 ppm for Ba; 13 ppm for Pb; and 14 ppm for Th. The time taken for determining Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th in a batch of 24 samples of komatiites, for a replication of four analyses per sample, by one operator, using a manual WDXRF spectrometer, is only 60 hours. 相似文献
12.
奥地利安东帕有限公司 《岩矿测试》2009,28(3):306-306
最新的流行病学研究表明,空气中较高浓度的悬浮细颗粒可能对人类的健康有不利的影响。根据该项研究显示,由于心脏病、慢性呼吸问题和肺功能指标恶化而导致死亡率的升高与细尘粒子有关。这些研究结果已经促使欧盟于1999年4月出台了限制空气中二氧化硫、二氧化氮、氧化氮、铅和颗粒物含量的法案(1999/30/EC),对各项指标包括对可吸入PM10颗粒的浓度提出了新的限制性指标。PM10颗粒是指可以通过预分级器分离采集的气体动力学直径小于10μm的细颗粒。目前研究的兴趣重点逐步偏向PM2.5这些更细微颗粒物,PM2.5这种颗粒物对健康有明显的不利影响。在欧盟指令2008/50/EC中,对PM10和PM2.5都提 相似文献
13.
E. M. Prasolov S. A. Sergeev B. V. Belyatsky E. S. Bogomolov K. A. Gruzdov I. N. Kapitonov R. Sh. Krymsky V. O. Khalenev 《Geochemistry International》2018,56(1):46-64
This paper reports the first results of a study of 11 isotope systems (3He/4He, 40Ar/36Ar, 34S/32S, 65Cu/63Cu, 62Ni/60Ni, 87Sr/86Sr, 143Nd/144Nd, 206–208Pb/204Pb, Hf–Nd, U–Pb, and Re–Os) in the rocks and ores of the Cu–Ni–PGE deposits of the Norilsk ore district. Almost all the results were obtained at the Center of Isotopic Research of the Karpinskii All-Russia Research Institute of Geology. The use of a number of independent genetic isotopic signatures and comprehensive isotopic knowledge provided a methodic basis for the interpretation of approximately 5000 isotopic analyses of various elements. The presence of materials from two sources, crust and mantle, was detected in the composition of the rocks and ores. The contribution of the crustal source is especially significant in the paleofluids (gas–liquid microinclusions) of the ore-forming medium. Crustal solutions were probably a transport medium during ore formation. Air argon is dominant in the ores, which indicates a connection between the paleofluids and the atmosphere. This suggests intense groundwater circulation during the crystallization of ore minerals. The age of the rocks and ores of the Norilsk deposits was determined. The stage of orebody formation is restricted to a narrow age interval of 250 ± 10 Ma. An isotopic criterion was proposed for the ore-bearing potential of mafic intrusions in the Norilsk–Taimyr region. It includes several interrelated isotopic ratios of various elements: He, Ar, S, and others. 相似文献
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Mining induced subsidence can significantly affect mining costs where major surface facilities and natural environment need to be protected. Overburden grout injection is a technology used to control coal mine subsidence by injecting the mine waste material extracted from the coal back into the inter-burden rock during longwall mining. The flowing slurry is here categorised as a nonlinear viscous cohesive (Bingham plastic) fluid. During longwall mining the grout slurry is pumped into the separated beds of the rock mass through a central vertical borehole, which is drilled deep into the inter-burden rock strata above the coal seam. However, a blockage can occur in the injection system when the slurry velocity falls below a certain critical threshold velocity, indicating a material phase change from cohesive-viscous to cohesive-frictional. In situ field injection tests through boreholes have been simulated at a smaller scale at the CSIRO laboratory in Brisbane by pumping the slurry through a radial disk (gap = 4 mm) from its centre. Laboratory experiments indicate a general, nonlinear, cohesive, viscous, frictional model for shear behaviour of the slurry, in which the material shear parameters are functions of the disk radial distance. Complete dimensional and dimensionless analytical solutions have been developed based on an approach related to Bingham–Herschel–Bulkley fluid mechanics. The derived formulae include relations for minimum pump pressure, local pressure and pressure gradient, wall shear stress, volume rate, velocity and velocity gradient. The theoretical results match the experimental measurements. The experiments covered slurries with maximum particle sizes of 0.5 to 2 mm with about 50% being larger than 100 µm. The viscosities at the various solids concentrations were measured with a standard torsion viscometer. This study differs from the previous research in several distinct aspects, namely, consideration of the variable shear parameters rather than fixed values, inclusion of total nonlinear behaviour, and implementation of a friction function to mimic behaviour of the deposited and consolidating stiff slurry, which can cause a significant pressure rise as a result of the increased shear resistance. 相似文献
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Between 1985 and 1991, two new mountain protected areas (MTNPA) covering more than 35,000 km2 and based on participatory management models — the Makalu-Barun National Park and Conservation Area, Nepal, and Qomolangma Nature Preserve, Tibet Autonomous Region — were successfully established through the collaborative efforts of Woodlands Mountain Institute and conservationists in China and Nepal. Characteristics common to both projects include the importance of establishing (1) effective rationales, (2) local support constituencies, (3) a senior advisory group, (4) a task force, (5) linkages between conservation and development, and (6) fund raising mechanisms. The lessons derived from the experiences of Woodlands Mountain Institute are of significant value to others in preserving MTNPA. Increased collaboration and communication between all interested in conservation, however, will remain a critical component for expanding mountain protected area coverage to throughout the world. 相似文献
19.
岩石密度和超高压岩石折返速率 总被引：1，自引：3，他引：1
在常温常压条件下对中国大陆科学钻CCSD主孔100-3000米岩心样品进行了密度测量,建立了密度连续剖面,并界定了不同超高压岩石的密度值。通过对比高温高压物性实验资料,岩石密度随着退变程度增强而降低,榴辉岩密度变化序列为3.52g/cm3→3.49g/cm3→3.07g/cm3→2.93g/cm3。超高压长英质岩石密度变化序列为3.00g/cm→2.80g/cm3→2.65g/cm3。上述实验资料是讨论不同折返阶段岩石所受浮力的基础,为研究折返速率大小提供了基本参数。本文通过折返板块运动平衡时,上浮力与粘滞力平衡这一关系式,定量研究了大陆俯冲板块的折返速率,认为密度差产生上浮力从而引起折返,温度对板块折返速率的影响最为显著;密度差大小、折返角度、折返板块大小对折返速率也有直接的影响。定量模拟分析表明,在温度高于850℃时,板块的折返速率可以超过100mm/a;当温度降至700℃时,折返速率则低于1.5mm/a。作者认为在折返早期,温度较高,板块快速折返至60-70km榴辉岩相深度;随着传导散热,温度降低,板块以较慢的速率折返至中下地壳。折返速率的估算表明,浮力是板块折返第一阶段(从>100km深部折返至<40km的中下地壳)的主要驱动力。 相似文献
20.
《Applied Geochemistry》2001,16(2):137-159
Five hundred and ninety-eight samples of terrestrial moss (Hylocomium splendens and Pleurozium schreberi) collected from a 188,000 km2 area of the central Barents region (NE Norway, N Finland, NW Russia) were analysed by ICP-AES and ICP-MS. Analytical results for Al, B, Ba, Ca, K, La, Mg, Mn, Na, P, Rb, Si, Sr, Th, U and Y concentrations are reported here. Graphical methods of data analysis, such as geochemical maps, cumulative frequency diagrams, boxplots and scatterplots, are used to interpret the origin of the patterns for these elements. None of the elements reported here are emitted in significant amounts from the smelting industry on the Kola Peninsula. Despite the conventional view that moss chemistry reflects atmospheric element input, the nature of the underlying mineral substrate (regolith or bedrock) is found to have a considerable influence on moss composition for several elements. This influence of the chemistry of the mineral substrate can take place in a variety of ways. (1) It can be completely natural, reflecting the ability of higher plants to take up elements from deep soil horizons and shed them with litterfall onto the surface. (2) It can result from naturally increased soil dust input where vegetation is scarce due to harsh climatic conditions for instance. Alternatively, substrate influence can be enhanced by human activity, such as open-cast mining, creation of ‘technogenic deserts’, or handling, transport and storage of ore and ore products, all of which magnify the natural elemental flux from bedrock to ground vegetation. Seaspray is another natural process affecting moss composition in the area (Mg, Na), and this is most visible in the Norwegian part of the study area. Presence or absence of some plant species, e.g., lichens, seems to influence moss chemistry. This is shown by the low concentrations of B or K in moss on the Finnish and Norwegian side of the (fenced) border with Russia, contrasting with high concentrations on the other side (intensive reindeer husbandry west of the border has selectively depleted the lichen population). 相似文献