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1.
比利亚谷铅锌银矿位于海拉尔—根河中生代火山盆地北西缘地区。该矿床赋存于上侏罗统满克头鄂博组酸性火山岩中,受北西向断裂构造控制,主矿体呈脉状产出。赋矿围岩流纹质火山角砾熔岩LA-ICP-MS锆石U-Pb测年结果表明,其成岩时代为(159.2±1.8)Ma,并依据赋矿围岩与成矿的关系推测成矿时代为晚侏罗世。矿床赋矿围岩流纹质火山角砾熔岩和流纹岩的主量元素具有富硅(68.31%~77.18%)、富钾(3.39%~4.28%)、低钠(0.14%~0.18%)、高铝(11.74%~14.93%)的特征,属高钾钙碱性系列;岩石REE总量较低(93.65×10~(-6)98.94×10~(-6)),以轻稀土相对富集、轻稀土和重稀土分异明显、弱的Ce负异常和Eu负异常为特征;结合岩石具有亏损Sr、高度富集轻稀土等特征认为火山岩产于板内,与其有关的岩浆可能来源于上地幔,并混染了壳源物质。综合本次研究和区域构造演化特征,初步认为矿床形成于鄂霍次克板块剪刀式闭合时期的拉张伸展环境。 相似文献
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锡林浩特东部早白垩世白音高老组岩石地球化学特征、LA-MC-ICP-MS锆石U-Pb年龄及地质意义 总被引：6，自引：0，他引：6
锡林浩特东部白音高老组火山岩主要由石泡流纹岩、珍珠岩、碎斑熔岩、流纹质熔结凝灰岩等组成。LA-MC-ICP-MS锆石U-Pb定年显示,火山岩形成于134 Ma~139 Ma之间的早白垩世。岩石地球化学研究表明:该组火山岩具有高硅、高钾、高Fe OT/Mg O比值(4.88~19.09),贫镁、钙特征,属高钾钙-碱性岩系;稀土元素表现为稀土总量较高(∑REE=82.02~436.61)、轻重稀土分馏明显(LaN/YbN=2.23~20.74)、属轻稀土富集型(LRE/HRE=2.71~11.87)、Eu负异常显著(δEu=0.06~0.42);微量元素特征表现为大离子亲石元素(LILE)Rb、Th、U、K相对较为富集,高场强元素(HFSE)Nb、Ta相对亏损,而Ba、Sr、Zr、Ti强烈亏损,与A2型花岗岩特征相似。其岩浆来源为典型的壳源岩浆系列,是陆壳岩石部分熔融的产物,形成于造山后的张性构造环境。 相似文献
3.
东天山卡拉塔格地区镁铁质岩体年代学、岩石地球化学研究 总被引：1，自引：1，他引：0
东天山大南湖岛弧带北缘卡拉塔格地区发育一系列镁铁质岩体,出露面积1km2。岩体岩相较为单一,主要岩性有辉长岩、橄榄辉长岩、橄长岩、淡色辉长岩和辉绿岩。本文利用LA-ICP-MS测得2个辉长岩的锆石U-Pb年龄分别为282. 2±0. 6Ma和278. 3±0. 6Ma;与吐哈盆地玄武岩及东天山地区铜镍硫化物矿床时代一致。岩石地球化学显示相对低Fe、高Al、Ca、碱、Ti,富集Rb、Ba、Sr、K,亏损Th、Nb、Ta的特征。岩石的(~(87)Sr/~(86)Sr)_i=0. 70313～0. 70461,εNd(t)=+6. 22～+8. 64,(~(206)Pb/~(204)Pb)_i=17. 68～18. 103,(~(207)Pb/~(204)Pb)_i=15. 443～15. 536,(~(208)Pb/~(204)Pb)_i=37. 423～37. 801,表现出高Nd、低Sr、低Pb,且变化范围较窄的特征。综合研究表明,该地区镁铁质岩体的岩浆动力学背景为后碰撞伸展环境;岩浆源区为俯冲板片交代的岩石圈地幔,并被软流圈物质混染;同位素和微量元素模拟显示母岩浆在源区遭受了5%～15%的板片流体交代,在上升过程中遭受了5%的上地壳物质混染。卡拉塔格地区镁铁质岩体与东天山二叠纪镁铁-超镁铁质岩体和吐哈盆地玄武岩形成于同一构造岩浆系统,在剥蚀较浅的大南湖岛弧带具有形成铜镍硫化物矿床的潜力。 相似文献
4.
在流纹质熔岩的气孔和裂隙中出现黄玉，表明母岩浆中F及亲F元素（Sn、W、Mo、Be、Li、Ta、Nb等）的含量很高，因此可能伴生有这些元素的火山成因或次火山成因的矿床。在墨西哥中央高原上分布极为广泛的黄玉流纹岩，与美国西部黄玉流纹岩的不同之处在于：①它们在科迪勒拉东部边缘的高原上呈线性带状产出，而不像美国西部的盆岭区那样呈大面积分布；②它们的年龄范围较窄，代表了大约在30Ma以前发生的岩浆幕，而不像美国西部那样代表在50Ma期间发生的一系列事件；③黄玉流纹岩分布区未出露前寒武纪岩石，而在美国人们通常假定黄玉流纹岩下伏有前寒纪岩石；④它们与双峰火山作用的伴生关系远不如美国西部那样清楚，而且不涉及玄武质岩石；⑤似乎没有含石榴石的黄玉流纹岩；⑥它们伴有大量的锡矿化，但在美国，黄玉流纹岩伴有克莱马克斯型斑岩钼矿床；⑦与此相当的侵入岩特别富B。直接与喷出的黄玉流纹岩穹丘有关的矿床仅包括：（1)玻斑状顶盖角砾岩、陆倾斜流动条带、交叉断裂中的喷气孔锡石和木锡矿以及边缘砂矿；（2）充填裂隙的宝石黄玉和宝石黄玉砂矿。明显地与同期岩浆作用有关的地下矿床包括（3）产于碳酸盐岩中的Ag-Pb-Zn脉状矿床和交代矿床；（4）近地表花岗岩接触带中的含铀萤石矿床；（5）与更深处花岗岩有关的矽卡岩／萤石／Zn-Pb-Ag/Sn/Be矿床。在Pinos、Zac地区流纹熔岩下之很厚的火山泥矿床，可能是由于岩浆与地表水的相互作用而形成的，这些与岩浆相互作用的地下水后来在平流循环时引起碳酸盐岩围岩中出现银矿化。 Spor山型的铍矿床可能产于某些黄玉流纹岩熔岩流还未出露的底部，但这还没有得以证实。 相似文献
5.
本文在对山西支家地银多金属矿床地质特征研究的基础上,对矿区出露的火山-次火山岩(流纹斑岩、石英斑岩、花岗岩)中的锆石做了系统的LA-ICP-MS U-Pb年龄测定:石英斑岩成岩年龄为135.4±0.8 Ma,流纹斑岩成岩年龄为136.2±0.6 Ma,花岗岩成岩年龄为136.2±0.7 Ma,其时代均为早白垩世,表明该区出露的火山–次火山岩属于同一期岩浆活动的产物。石英斑岩与成矿关系密切,其成岩年龄135 Ma可以近似作为支家地矿床的成矿年龄。流纹岩和石英斑岩在化学成分上表现为富硅(SiO_2=72.43%~78.48%)、高钾(K_2O/Na_2O值平均为25.17)、强过铝质(A/CNK=1.24~1.95),二者稀土元素和微量元素特征非常类似,微量元素明显富Rb、Th、K、La、Nd、Zr等、相对亏损大离子亲石元素Ba、Sr、Eu等元素,Ti含量较低,属轻稀土元素富集型的钾玄岩系列过铝质花岗岩类,花岗岩仅在P和K元素化学成分上与前2者相差比较大(石英斑岩和流纹岩富K,亏损P,而花岗岩反之)。矿区三类岩石地球化学特征显示其具后碰撞花岗岩的特征,推测其可能形成于后碰撞伸展环境。本次所获锆石U-Pb年龄,不仅丰富了研究区火山-次火山岩类的同位素年龄资料,也为建立中生代构造–岩浆–成矿事件提供了重要信息。 相似文献
6.
内蒙古二道河子铅锌矿成因研究 总被引：1，自引：0，他引：1
基于矿床地质调查,并通过岩矿石地球化学和锆石U-Pb测年研究,探讨了二道河子铅锌矿床成因。该矿床赋存于中侏罗统塔木兰沟组中,受北西向断裂-裂隙构造控制,矿体多呈脉状,围岩以火山岩为主,夹有砾岩。据常量、微量、稀土元素和Pb、Sr、Nd同位素测试结果:火山熔岩中SiO2质量分数为48.01%～56.44%,岩屑晶屑凝灰岩中为69.09%～71.73%。前者稀土总量高于后者,两者稀土配分型式相似,均显弱负铕异常;而前者Pb、Zn、Cu等成矿元素的含量却远低于后者。火山岩富集Rb、U、Th等大离子亲石元素,Sr普遍亏损,相对亏损Nb、Ta以及Ti等高场强元素。火山岩ISr=0.704 925～0.706 632,εNd(t)=0.5～2.0,εSr(t)=8.5～32.8,tDM=619～730Ma。火山岩和矿石的Pb同位素组成十分接近,206Pb/204Pb=18.130～18.475,207Pb/204Pb=15.526～15.567,208 Pb/204 Pb=38.078～38.286,μ值为9.32～9.40。矿床主要围岩岩屑晶屑凝灰岩的SHRIMP锆石U-Pb年龄为(164.2±2.3)Ma,这表明火山岩为混有壳源物质的幔源岩浆形成。火山活动分为2期:早期表现为中(基)性火山喷发;晚期岩浆活动发生于中侏罗世晚期,形成酸性火山碎屑岩。成矿物质由与火山岩有关的岩浆系统提供,富集于晚期岩浆中。与成矿有关的侵入岩可能是晚期岩浆作用形成的次火山岩。矿床可能是岩浆分异的含矿热液沿火山岩中的断裂、裂隙充填交代形成,成矿时代为中侏罗世晚期—晚侏罗世。 相似文献
7.
内蒙古东南部正蓝旗地区中生代火山岩广泛出露,岩性主要包括流纹岩、粗面岩、碎斑熔岩、熔结凝灰岩以及黑曜岩等,以碎斑熔岩发育为显著特征。本次研究测得流纹岩、霏细质碎斑熔岩及熔结凝灰岩的LA-ICP-MS锆石U-Pb年龄分别为(141.4±0.7)Ma、(141.6±0.6)Ma和(139.4±0.7)Ma,三者在误差范围内一致,表明研究区火山活动(从溢流、爆发到侵出)持续的时间很短,时代为早白垩世早期,属张家口组。除个别样品,正蓝旗地区晚期侵出的碎斑熔岩与早期溢流相的流纹岩、粗面岩在地球化学特征上极为一致,均为富硅富钾,贫Ca、Mg和Al,属粗面岩-流纹岩组合,部分样品具有碱性流纹岩的特征;富集Rb、Th、U等大离子亲石元素,而强烈亏损Ba、Sr、Ti、P;轻稀土元素(LREE)富集,Eu强烈亏损,轻、重稀土元素分馏较强(LaN/YbN主要介于6.87~42.74)。碎斑熔岩体相较于早期熔岩更加富硅贫碱,表明流纹岩-粗面岩喷溢之后,岩浆房中剩余岩浆又经过一定程度的分异,向更为富硅贫碱方向演化之后侵出地表。正蓝旗地区火山岩具有A型花岗岩的特征,为A_1型为主,A_1—A_2过渡的地球化学特征。碎斑熔岩体与流纹岩-粗面岩的Nb/Ta介于10.46~24.02,在地壳和地幔岩浆Nb/Ta比值之间;Y/Nb、Ti/Yb、Ti/Zr均体现出壳幔混合的特点;Rb/Sr介于0.61~64.51,为壳源特征。因此,研究区火山岩是造山后向板内非造山转换并以板内非造山为主的伸展环境下,经较为强烈地幔物质改造的下地壳部分熔融的产物。 相似文献
8.
渣尔泰山地区白垩纪酸性火山岩地质特征及成矿作用 总被引：2，自引：2，他引：0
渣尔泰山地区位于内蒙古中西部,大地构造位置处于华北地台北缘狼山-渣尔泰山裂陷槽的东段,根据近几年的找矿实践与研究,在白垩纪的酸性火山岩中已发现银金矿床、金银矿床,主要赋存于下白垩统白女羊盘组酸性火山岩中。该套火山岩具富硅富钾、相对贫钙镁的特点,属于铝过饱和的碱性系列;在球粒陨石标准化图解上岩石化学样品均显示为轻稀土(LREE)相对富集、重稀土(HREE)相对亏损的右倾型配分模式,轻重稀土分异较明显,显示较明显的负铕异常;微量元素显示明显的Rb、Pb正异常和Ba、Sr负异常,不相容元素比值Zr/Nb=2.47~4.87,Zr/Y=18.3~103。属大陆碰撞造山期后作用的产物,来源于地壳部分熔融。其岩石类型主要有:流纹质凝灰角砾岩、流纹质角砾凝灰岩、球粒状流纹岩、珍珠岩、显微嵌晶状流纹岩夹流纹斑岩等。银多金属矿的含矿层主要由复碎裂复硅化流纹质凝灰角砾岩、硅化复碎裂流纹岩、多期次硅化黄铁矿化角砾岩化流纹斑岩等组成。成矿元素Ag、Au、Sb、W显著富集于流纹质凝灰角砾岩、多期次硅化碎裂的流纹岩、流纹斑岩中,其平均含量高于中国流纹岩元素丰度10倍以上,说明该套火山岩提供了成矿物质来源;且元素含量的分异程度较大,指示明显受到后期成矿作用的叠加;有一定的找矿潜力。 相似文献
9.
湘南西山花岗质火山-侵入杂岩形成时代的确定 总被引：6，自引：0，他引：6
湖南南部西山火山侵入杂岩中3个代表性岩石单元(花岗岩、碎斑熔岩和流纹岩 )的产状、岩石化学、微量元素和同位素地球化学特征显示 ,它们同空间、同物质来源。全岩Rb Sr定年结果表明 :花岗岩、碎斑熔岩和流纹岩的形成时代分别为156±6Ma、159±2Ma和154±11Ma ,87Sr/86Sr初始值分别为0.71779、0.71738和0.71774 ,其中碎斑熔岩的锆石SHRIMP定年结果为156±2Ma ,它们在误差范围内基本相同 ,为中侏罗世晚期同一构造岩浆事件中陆壳活化的产物。 相似文献
10.
新疆谢米斯台布拉特矿化次火山岩的年代学、地球化学特征及其地质、成矿意义 总被引：1，自引：1，他引：0
布拉特矿化次火山岩出露于谢米斯台中部,岩性主要为英安斑岩和流纹斑岩。本文通过锆石U-Pb年代学、岩石地球化学和Sr-Nd-Hf同位素等研究,探讨其形成的构造环境、成因及成矿意义。结果表明,英安斑岩形成年龄为434.9±2.3Ma,属高钾钙碱性-钾玄岩系列准铝质-强过铝质岩石;岩石稀土总量中等(∑REE=97.9×10~(-6)～107×10~(-6)),富集轻稀土且轻重稀土分异明显((La/Yb)_N=7.93～9.95),具较弱铕负异常(δEu=0.78～0.90),相对富集Rb、Th、U、K等元素,亏损Nb、Ta、P、Ti等元素;岩石具有低的(~(87)Sr/~(86)Sr)_i值(0.7036～0.7043)和正的ε_(Nd)(t)值(+2.64～+5.01),t_(DM1)(Nd)=750～930Ma。流纹斑岩形成年龄为423.2±0.9Ma,属高钾钙碱性-钾玄岩系列准铝质-强过铝质岩石;稀土总量中等(∑REE=65.3×10~(-6)～127×10~(-6)),富集轻稀土且轻重稀土分异明显((La/Yb)_N=6.82～8.24),具较强铕负异常(δEu=0.51～0.71),相对富集Rb、Th、U、K等元素,亏损Nb、Ta、P、Ti等元素;岩石具有低的(~(87)Sr/~(86)Sr)_i值(0.7022～0.7038)和正的ε_(Nd)(t)值(+2.86～+5.78),t_(DM1)(Nd)=680～940Ma;锆石ε_(Hf)(t)=+9.8～+14.9,t_(DM2)(Hf)=456～783Ma。综合研究表明,布拉特矿化英安斑岩和流纹斑岩是不同岩浆演化结晶的产物,二者都形成于活动大陆边缘弧环境,可能是新生下地壳部分熔融形成的花岗质岩浆与部分源自地幔楔的玄武质岩浆发生混合、向上运移、冷凝结晶的产物。较晚形成的流纹斑岩岩浆形成过程中新生下地壳部分熔融的比例有所降低,熔出的岩浆相对更偏酸性;谢米斯台地区以志留纪-早泥盆世火山岩、次火山岩和中酸性侵入体为代表的岩浆岩带为一个主体形成于早古生代的陆缘弧岩浆岩带,是形成和寻找斑岩型铜矿的有利地区。 相似文献
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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
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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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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
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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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Alexander E. C. Broberg J. S. Kehren A. R. Graziani M. M. Turri W. L. 《Environmental Geology》1993,22(4):353-361
Bellechester, Minnesota, is a small community of approximately 155 residents located on the county line between Goodhue and Wabasha counties in southeast Minnesota's karst region. Bellechester is served by a 21-year-old wastewater treatment facility (WWTF) consisting of three waste-stabilization ponds. On 28 April 1992 six sinkholes were discovered to have drained cell 2 of the WWTF resulting in the loss of approximately 8.7×106 1 of partially treated effluent and about 600 m3 of soil into previously undetected subsurface voids of unknown dimensions. In the week following the collapse, approximately 200 water wells located within a 5-km radius of the WWTF were sampled in an after-the-fact, emergency sampling program. Twelve samples with elevated fecal coliform levels, 18 samples with nitrate-nitrogen greater than the 10 mg/1 standard, and no samples with elevated chlorides were found. However, the elevated levels could not be unambiguously attributed to the WWTF collapse. This is the third WWTF to fail by sinkhole collapse in southeast Minnesota since 1974. All three collapsed lagoons have been located in similar geomorphic and stratigraphic settings. However, at least two lagoons have collapsed in the adjacent area in northeast Iowa, and these lagoons are located at different stratigraphic positions. Twenty-two WWTFs constructed in southeast Minnesota's karst region in the last 25 years have been identified as subject to potential sinkhole collapse. An unknown but significant number of manure storage lagoons, flood control structures, etc., have also been constructed in the karst region and are at risk. Public agencies are beginning to develop plans to deal with the risk associated with existing and future waste lagoons in this environment. The critical hydrogeologic parameters that can be used to prioritize the risk of collapse at existing facilities include: (1) the lithology of the first bedrock beneath each lagoon, (2) the thickness of surficial materials between the lagoon and the bedrock surface, (3) the presence and construction of liners (seepage rate), and (4) the proximity to existing sinkholes. 相似文献
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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
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滇东南锡、银、铅、锌多金属矿床主要分布在个旧、白牛厂、都龙3个矿区,而滇东南较大的3个花岗岩体又分别出露在3个矿区或附近.花岗岩体均形成于燕山晚期,岩石化学、矿物成分相似,富含锡、银、铅、锌、钨、铜等成矿元素.矿床主金属元素组合与岩体之间的距离由远而近出现由锡、钨、(铍、铌、钽)→锡、钨、(铁)、铜、铟→锡、铅、锌、银、铟、(锑)有规律的变化.花岗岩浆是成矿物质来源和成矿热源.岩浆侵入初期使上覆地层隆起产生背斜(凹陷部位成向斜);同时使地层产生一系列裂隙、压性断层或层间断裂;岩浆侵入晚期,这些断层再次活动,表现为张性,岩浆产生的含矿热液沿由其活动所造成的断裂迁移、充填、交代、沉淀而形成矿床. 相似文献