北山辉铜山泥盆纪钾长花岗岩锆石U-Pb年龄、 成因及构造意义

LA-ICP-MS锆石U-Pb定年结果表明,北山柳园地区辉铜山钾长花岗岩的形成年龄为397±3Ma (MSWD=1.1).地球化学特征显示为高钾钙碱性的高分异Ⅰ型花岗岩到A型花岗岩过渡的特征.其全岩εNd(t)值为-1.3～ +1.2,Nd模式年龄(tDM)为960 ～ 1530Ma;锆石εHf(t)值为-1.0～ +5.8,两阶段Hf模式年龄(tDM2)为1024～1455Ma.地质背景、地球化学和同位素综合分析显示,辉铜山岩体为造山后伸展拉张背景下,幔源岩浆底侵导致上覆年轻地壳(可能为洋壳、岛弧建造或增生楔物质)部分熔融形成的钙碱性花岗闪长质岩浆经进一步演化及结晶分异形成.北山南带地区早-中泥盆世花岗岩显示出高分异钙碱性Ⅰ型花岗岩、I-A型花岗岩和A型花岗岩的组合特征.因此,在397Ma左右,北山地区古生代岩浆已经从Ⅰ型或S型转化为I-A型特征,构造环境转化为后造山或同造山晚期的伸展环境.     

内蒙古武川西乌兰不浪地区早前寒武纪变质基底锆石SHRIMP定年及Hf同位素组成

本文报道了华北克拉通西部武川西乌兰不浪地区太古宙变质基底的锆石SHRIMP年龄和Hf同位素组成。一个片麻状奥长花岗岩样品的锆石具核边结构,核部岩浆锆石和边部变质锆石的207Pb/206Pb加权平均年龄分别为2692±17Ma和2528±16Ma。对9个样品进行了锆石Hf同位素分析。新太古代早期(2692～2697Ma)片麻状奥长花岗岩(2个样品)的岩浆锆石的εHf(t)、tDM1(Hf)和tDM2(Hf)分别为4.78～8.83、2646～2780Ma和2632～2845Ma;新太古代二辉麻粒岩(2个样品)中的捕获锆石的εHf(t)、tDM1(Hf)和tDM2(Hf)分别为-2.30～8.62、2543～2954Ma和2529～3189Ma;新太古代变质深成岩(4个样品)的岩浆锆石的εHf(t)、tDM1(Hf)和tDM2(Hf)分别为-2.60～8.09、2529～2880Ma和2538～3089Ma;古元古代蓝晶石榴长英质片麻岩(1个样品)的碎屑锆石的εHf(t)、tDM1(Hf)和tDM2(Hf)分别为1.52～6.59、2432～2774Ma和2498～2925Ma。结合前人研究结果,可得出如下结论和认识:1)该区存在新太古代早期片麻状奥长花岗岩,太古宙岩石在新太古代晚期普遍遭受高级变质作用影响;2)新太古代早期为该区地壳形成主要时期,新太古代晚期则主要表现为陆壳物质再循环;3)作为阴山地块的典型代表,固阳-武川地区与华北克拉通东部太古宙基底十分类似,可能表明华北克拉通在新太古代晚期已成为统一的整体。     

甘肃北山明舒井岩体形成年龄、地球化学特征及其地质意义

北山明舒井岩体为一由辉长岩、闪长岩和花岗岩构成的岩浆杂岩体。LA-ICP-MS锆石U-Pb定年分别获得辉长岩442.9±1.2Ma、闪长岩437.0±2.3Ma、花岗岩435.9±2.2Ma的形成年龄。其中,辉长岩为富钙、高铁和镁的钙碱性岩,相对富集LREE和LILE、贫化HFSE,亏损Nb、Ta、Ti、Zr和P,Pb正异常,具中等偏高的(87Sr/86Sr)i(0.705892)、高放射性成因Pb,低εNd(t)(0.1),锆石εHf(t)变化大(-7.1~+8.3)。闪长岩和花岗岩富钠、低钙、铁和镁,为准铝质钙碱性岩;它们富集LREE和LILE、亏损HFSE,Nb、Ta及Sr、P、Ti明显负异常;也显示中等偏高的(87Sr/86Sr)i(0.705951~0.706196)和高放射性成因Pb、低εNd(t)(-0.2~-0.1),但锆石εHf(t)明显偏正(-1.1~+12.0)。不同岩类的地球化学特征及其相对一致的Sr-Nd-Pb同位素及明显不同的锆石Hf同位素,指示它们形成于板块消减带构造环境,为源自受流体交代和陆壳物质改造的幔源岩浆与新元古代陆壳物质部分熔融的岩浆混合和分离结晶演化的产物,代表北山南部早古生代晚奥陶世-早志留世晚期与大洋俯冲消减作用有关的构造岩浆事件。     

东天山大南湖-头苏泉岛弧带古生代侵入岩浆活动期次及基底性质

锆石U-Pb定年结果显示:东天山大南湖-头苏泉岛弧带中酸性侵入岩形成时代为古生代,处于465～265Ma,可划分为4个期次。分别为:中奥陶世—晚志留世465～413 Ma、中—晚泥盆世391～377Ma、石炭纪327～308Ma,以及早—中二叠世284～269 Ma。锆石Hf同位素分析显示,锆石εHf(t)值为6.81～15.73,Hf同位素二阶段模式年龄为839～355 Ma,主要集中在598～429Ma;465～413Ma的侵入岩分布在卡拉塔格和大南湖,其εHf(t)值为11.34～15.20,相应的Hf同位素二阶段模式年龄为633～467 Ma;391～377 Ma的侵入岩分布于卡拉塔格,其εHf(t)值为6.81～13.32,相应的Hf同位素二阶段模式年龄为839～497Ma;327～308Ma的侵入岩分布在黄山西以及沁城南,其εHf(t)值为11.36～15.73,相应的Hf同位素二阶段模式年龄为575～429Ma;284～269Ma的侵入岩分布在土屋西和推克曼塔什,其εHf(t)值为8.94～14.51,相应的Hf同位素二阶段模式年龄是671～355Ma。再结合前人的研究成果揭示,在大南湖-头苏泉岛弧带底部可能存在老的地壳基底,并对这些岩浆活动有所贡献;该区古生代期间存在大约465 Ma早奥陶世以及330Ma左右中石炭世2期地壳增生事件,并存在晚奥陶世—晚志留世、中—晚泥盆世和早—中二叠世三期地壳再造事件。     

内蒙古中部苏尼特左旗大石寨组流纹岩SHRIMP锆石U-Pb年龄、地球化学特征及其构造意义

内蒙古中部苏尼特左旗地区大石寨组酸性火山岩SHRIMP锆石U-Pb测年结果显示,2件流纹岩样品的206Pb/238U年龄加权平均值分别为272.1±3.1Ma和271.4±1.7Ma,说明大石寨组流纹岩喷发于早二叠世。锆石Hf同位素分析结果表明,εHf(t)值为+10.8~+13.1;Hf-Nd同位素耦合关系计算显示,其与同期形成的大石寨组玄武岩Nd同位素组成特点非常相似。全岩地球化学分析表明,该流纹岩高Si O_2,贫Ca O、Fe_2O_3*和Mg O,大部分样品属于过铝质、钙碱性流纹岩;富集轻稀土元素,轻、重稀土元素分馏中等,具明显的负Eu异常,富集Cs、Rb、Th、U和Zr,亏损Ba、Sr、Nb、Ta、P和Ti,指示其是富水的钙碱性基性地幔岩浆分离结晶作用的产物。结合区域地质资料,认为苏尼特左旗流纹岩形成于大陆岛弧背景。     

北大别早白垩纪花岗岩类的Sm-Nd和锆石Hf同位素及其构造意义

大别造山带产出两期早白垩纪造山后花岗岩类:早期(≈132Ma)变形的角闪石英二长岩和斑状二长花岗岩具高钾的类埃达克岩的地球化学特征,形成于增厚地壳(>50km)的下地壳部分熔融;晚期(≈128Ma)未变形的花岗岩包括细粒二长花岗岩和钾长花岗(斑)岩,属于正常安山岩-英安岩-流纹岩系列岩石,它们形成于相对薄的地壳(<35km)的下地壳部分熔融。早期变形的花岗岩类中,角闪石英二长岩的(~(87)Sr/~(86)Sr)_i=0.7066～0.7076,ε_(Nd)(t)=-20.3～-27.8,类似于扬子下地壳基性麻粒岩的Sr-Nd同位素特征,其中白垩纪岩浆锆石(≈132Ma)Hf同位素初始比值(ε_(Hf)(t))和两阶段Hf模式年龄(t_(DM2))分别为-29.30.5和303065Ma;我们认为角闪石英二长岩源于锆石Hf模式年龄约3.0Ga的基性下地壳部分熔融。早期斑状二长花岗岩的(~(87)Sr/~(86)Sr)_i=0.7078～0.7083,ε_(Nd)(t)=-15.8～-20.0,类似于北大别英云闪长质-花岗质片麻岩的Sr-Nd同位素特征,其白垩纪岩浆锆石(≈132Ma)的ε_(Hf)(t)和t_(DM2)分别为-24.80.5和274434Ma。我们认为宽状二长花岗岩源于约2.7Ga的中酸性下地壳部分熔融。晚期未变形的花岗岩的(~(87)Sr/~(86)Sr)_i=0.7069～0.7105,ε_(Nd)(t)=-16.4～-22.1,类似于北大别英云闪长质-花岗质片麻岩的Sr-Nd同位素特征;其白垩纪岩浆锆石(≈128Ma)的ε_(Hf)(t)具有较大的变化范围(-25.2～7.4),主要峰值为-22.5±0.5,次要峰值为-16.3±0.7,并有少量正的ε_(Hf)(t)值5.8～7.4,与ε_(Hf)(t)值对应的t_(DM2)分别为2600±40Ma、2211±68Ma和743±130Ma。我们认为晚期未变形的花岗岩源于锆石Hf模式年龄约2.6～2.2Ga的中酸性下地壳部分熔融,源区夹杂新元古代新生的陆壳。在大别造山带垮塌之前(>132Ma),增厚地壳(>50km)的下地壳存在双层结构:锆石Hf模式年龄约为3.0Ga的基性下地壳基底和约2.7Ga的中酸性(英云闪长质-花岗质)上部下地壳.在大别造山带伸展垮塌的晚期阶段(≈128Ma),减薄的下地壳(<35km)主要为锆石Hf模式年龄约2.6～2.2Ga的中酸性(英云闪长质-花岗质)岩石,并夹杂少量新元古代Rodinia超大陆裂解时形成的新生陆壳。     

赣东北地区福泉山岩体高分异S型花岗岩成因:来自锆石U-Pb年龄、Hf同位素及地球化学的证据

福泉山岩体位于赣东北地区,为揭示其成因及形成构造背景,对福泉山岩体进行了锆石U-Pb年龄、Hf同位素和全岩地球化学研究.其中锆石LA-ICP-MS定年结果显示,该岩体的形成年龄约为130 Ma,为早白垩世,属燕山晚期岩浆活动的产物.锆石εHf(t)值为-5.47～-1.51,tDM2为1255～1668 Ma.该岩体地...     

华北板块北缘东段二叠纪的构造属性:来自火山岩锆石U-Pb年代学与地球化学的制约

本文对华北板块北缘东段大河深组、关门咀子组火山岩进行了锆石LA-ICP-MSU-Pb定年和岩石地球化学研究以便制约该区的区域构造演化。大河深组和关门咀子组火山岩中的锆石均呈自形-半自形晶,具有清晰的岩浆振荡生长环带和条痕状吸收(玄武安山岩)的特点,其Th/U比值高达0.31～1.56,表明其岩浆成因。测年结果表明,桦甸大河深组流纹岩形成于早二叠世(279±3Ma～293±2Ma),珲春和图们关门咀子组玄武安山岩和玄武岩分别形成于早二叠世(275±7Ma)和晚二叠世(250±5Ma)。大河深组火山岩SiO2含量介于64.9%～75.4%,Mg#值介于0.21～0.57,属于中钾-高钾钙碱性系列,明显富集轻稀土元素(LREEs)和大离子亲石元素(LILEs)、亏损高场强元素(HFSEs,如Nb、Ta、Ti)以及P元素,类似活动大陆边缘火山岩;其锆石的εHf(t)值为+0.9～+10.37,Hf同位素二阶段模式年龄值为785～1240Ma,表明它们均起源于中-新元古代新增生玄武质下地壳的部分熔融。珲春早二叠世关门咀子组属于中钾钙碱性系列;贫硅(53.4%～53.7%)和HFSEs,富铝(16.4%～16.8%)和LILEs,具有较低的稀土元素总量,以及较平坦的稀土配分型式,显示出岛弧火山岩的地球化学属性;该组火山岩的原始岩浆应起源于受俯冲板片脱水熔融交代的亏损地幔楔。图们晚二叠世关门咀子组玄武岩SiO2含量为48.7%～49.6%,Mg#值高达0.64～0.72,相对富集LREEs和LILEs,亏损HREEs和HFSEs,具有火山弧玄武岩的地球化学属性,同时其εNd(t)=+6.01,暗示其原始岩浆起源于亏损的岩石圈地幔。综上所述,我们认为早二叠世至晚二叠世期间,华北板块北缘东段(吉林中部地区)和兴凯地块西南缘均处于古亚洲洋的俯冲作用下。     

湘西及邻区晚震旦世—早二叠世黑色岩系的沉积环境——Ce、Nd同位素制约

测定了湘西及邻区晚震旦世—早二叠世25个黑色岩系样品的La-Ce和Sm-Nd同位素数据。它们的εCe(t) 和εNd(t) 值分别变化在- 1.6 ～+ 2.6和- 1.4 ～- 11.0范围内,δCe值为0.28 ～1.68 ,T2 DM 年龄为1358 ～2207 Ma。在εCe(t)-εNd(t) 图上,全部数据点可以分成3个区,不同的分区显示了黑色岩系的不同沉积环境与构造背景。在沉积环境研究中Ce同位素是有用的地球化学示踪器。     

长江源各拉丹冬地区晚三叠世火山岩锶、钕同位素地球化学特征及其意义

对各拉丹冬地区晚三叠世火山岩进行了颗粒锆石U-Pb测年和Sr、Nd同位素分析,颗粒锆石的U-Pb年龄值为(212±1.7)Ma,全岩样品的ISr、εNd(t)和Nd模式年龄tDM变化在0.70325~0.70917、-0.8~-4.6和1064~1379Ma之间。分析结果表明,形成晚三叠世火山岩的原始岩浆是壳幔混合型。结合岩石化学、稀土元素、微量元素等特征,该套火山岩的形成与岛弧-活动陆缘环境有关。     

Wavelength-dispersive X-ray fluorescence spectrometric determination of Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th in komatiites

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.     

硅酸盐类样品中硅、铁、铝、钛、锰、钙、镁、钾、钠和磷的x射线荧光光谱测定

本文拟定了一种以熔融法制备样片,用X射线荧光光谱测定硅酸盐类样品中Si、Fe、Al、Tj、Mn、Ca、Mg、K、Na、P等元素的分析方法。在对不同靶材X光管和分光晶体实验对比的基础上,选择了最佳的测量条件。该法具有快速、准确,测量范围广,检测限低,价格便宜等优点。经过近百个各种类型标样或管理样品的分析对比表明,本法不仅适用于硅酸盐类岩石样品的分析,还适用于铁矿、铝土矿、碳酸盐类岩矿样品以及水泥、耐火材料等样品的分析。     

高压微波消解法测定醋酸纤维过滤器采集的微尘粒子中的砷镉钴铬铜铁锰镍铅钒锌

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     

Isotopic systematics of He,Ar, S,Cu, Ni,Re, Os,Pb, U,Sm, Nd,Rb, Sr,Lu, and Hf in the rocks and ores of the Norilsk deposits

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.     

Viscous, cohesive, non-Newtonian, depositing, radial slurry flow

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.     

硅酸盐中铁、锰、钛、钙、钾、磷、硅、铝、镁、钠、锶、铷、钡的X-射线荧光光谱定量测定

本文介绍样品经四硼酸锂熔融制成玻璃小饼。采用Lachance模式和理论a系数来校正元素间的效应,由3080E型X-射线荧光谱仪和DF-350B数据处理系统完成硅酸盐中十三个项目的测定。     

Bellechester,Minnesota, USA,lagoon collapses

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.     

Mercury,arsenic, antimony,and selenium contents of sediment from the Kuskokwim River,Bethel, Alaska,USA

The Kuskokwim River at Bethel, Alaska, drains a major mercury-antimony metallogenic province in its upper reaches and tributaries. Bethel (population 4000) is situated on the Kuskokwim floodplain and also draws its water supply from wells located in river-deposited sediment. A boring through overbank and floodplain sediment has provided material to establish a baseline datum for sediment-hosted heavy metals. Mercury (total), arsenic, antimony, and selenium contents were determined; aluminum was also determined and used as normalizing factor. The contents of the heavy metals were relatively constant with depth and do not reflect any potential enrichment from upstream contaminant sources.     

滇东南花岗岩与锡、银、铜、铅、锌多金属矿床的成因关系

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.     

岩石密度和超高压岩石折返速率

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。