额尔古纳地块新元古代岩浆作用与微陆块构造属性:来自侵入岩锆石U-Pb年代学、地球化学和Hf同位素的制约

对额尔古纳地块新元古代花岗岩进行了锆石LA-ICP-MS U-Pb年代学、岩石地球化学和锆石Hf同位素研究,以便对其新元古代岩浆作用历史与微陆块构造属性给予制约.所测花岗质岩石中锆石的CL图像特征和Th/U比值(0.17~1.46) 显示其为岩浆成因.测年结果并结合前人定年结果,可以判定额尔古纳地块上至少存在~929 Ma、~887 Ma、~850 Ma、~819 Ma、~792 Ma、~764 Ma和~738 Ma岩浆事件.岩石地球化学特征显示,~887 Ma花岗岩为一套后碰撞花岗岩类;而850~737 Ma花岗质岩石整体上属于A-型花岗岩,也有部分岩体(漠河、阿木尔、碧水和室韦岩体)显示I-型花岗岩特征.锆石Hf同位素特征反映这些花岗岩的源区既有中-新元古代(T_DM2=884~1 563 Ma)新增生地壳物质的部分熔融,同时伴有少量古老地壳物质的混染,也有残留的古老中基性下地壳物质的部分熔融.综合研究区新元古代侵入岩的地球化学特征,同时对比新元古代全球构造热事件,认为额尔古纳地块上新元古代岩浆活动记录了Rodinia超大陆形成和演化过程中的地壳响应:927~880 Ma的岩浆作用应是Rodinia超大陆汇聚造山的产物;而850~737 Ma的岩浆作用应是对Rodinia超大陆快速裂解的记录.通过岩浆事件对比发现,额尔古纳地块与邻近的西伯利亚南缘微陆块(如中蒙古地块和图瓦地块)具有亲缘性,而与塔里木板块和华南板块至少在新元古代岩浆活动上具有一定的相似性,而明显区别于华北板块和西伯利亚板块.      

华北克拉通对Rodinia超大陆裂解的响应——来自贺兰山北段小松山地区辉长岩地球化学、年代学及Hf同位素的新证据

华北克拉通西缘贺兰山北段小松山地区辉长岩锆石U-Pb年代学、岩石地球化学和锆石Hf同位素的研究结果表明,辉长岩的侵位结晶年龄为835.5±5.3Ma,即形成于新元古代早期,属于板内拉斑玄武岩系列岩石,总体上略富集轻稀土元素、大离子亲石元素Rb、Ba、La,略亏损高场强元素Th、Nb、Zr、Hf等;具有较高的εHf(t)值(5.83~7.87),其单阶段模式年龄tDM1为1075~1155Ma,两阶段模式年龄tDM2为1176~1289Ma。综合研究发现,辉长岩的原始岩浆起源于中元古代富集型地幔,形成于华北陆块西缘的板内伸展环境,说明华北陆块响应了Rodinia超大陆裂解,也是Rodinia超大陆的一部分。     

南秦岭桐柏地区程湾花岗岩LA-MC-ICP-MS锆石U-Pb年龄及地球化学特征

程湾花岗岩位于南秦岭桐柏地区,岩性主要为片麻状(黑云母)正长花岗岩,岩石地球化学成分显示其高硅、富碱、贫镁、低磷和低钛的特征,A/CNK=0.99~1.40,平均为1.17,为高钾钙碱性系列过铝质岩石,稀土元素配分曲线总体表现为右倾斜的"海鸥式",具有负Eu异常(δEu=0.11~0.81,平均0.46)。岩石富集高场强元素Zr、Th、Hf和Rb、K,强烈亏损Ba、Sr、P、Ti,10000Ga/Al值在2.84~3.63之间,计算锆石饱和温度为817~879℃,属于A2型花岗岩。正长花岗岩LA-MC-ICP-MS锆石UPb测年结果表明,其~(206)Pb/~(238)U年龄加权平均值为793.0±4.1Ma,表明岩体形成于新元古代青白口纪晚期,而非前人认为的早古生代,其形成与Rodinia超大陆的裂解有关,且形成于裂解的初期阶段。桐柏地区当时仍为扬子大陆北缘的南秦岭,在新元古代中—晚期(825~611Ma)整体上处于陆内裂解的构造体制。     

冀北小张家口超基性岩体的锆石U-Pb年龄和Hf同位素组成

采用离子探针(SHRIMPⅡ)测得小张家口基性-超基性岩体中的锆石主要有220±5Ma和491±7Ma两组年龄,以及一个很老的继承锆石年龄2453Ma。年龄为220±5Ma的一组锆石(A组)具有典型的岩浆型振荡环带,这组年龄应代表该岩体的侵位年龄。A组锆石的~(176)H/~(177)Hf比值从0.282557到0.282690,ε_(Hf)(220Ma)=-2.9～ 1.66。年龄为491±7Ma的一组锆石(B组)具有变质成因的蝴蝶结构(Butterfly structure)和熔蚀边,属于继承锆石。B组锆石的~(176)Hf/~(177)Hf比值从0.282239到0.282483,ε_(Hf)(491Ma)=-8.6～0.06。~(207)Pb/~(206)Pb年龄为2453Ma的锆石应该是岩浆侵位时从华北克拉通古元古代基底中捕获的锆石。A组锆石的Hf同位素数据表明,220Ma左右由于华北北缘岩石圈伸展,导致软流圈地幔上涌,亏损的软流圈地幔流/熔体与富集的岩石圈地幔相互作用并混合,这种混合地幔源区发生部分熔融而形成小张家口基性-超基性岩体。B组锆石可能是小张家口岩体在岩浆侵位过程中捕获的来源于富集地幔或大陆下地壳的锆石。     

塔里木北缘Rodinia超大陆聚合事件——来自新元古代早期花岗岩成因的证据

对塔里木板块拼入Rodinia超大陆聚合时限进行限定,报道塔里木板块北缘库鲁克塔格隆起奥依库如克岩体花岗闪长岩的年代学、岩石学、地球化学和锆石Hf同位素特征。花岗闪长岩的LA-ICP-MS锆石U-Pb年龄为(855±29)Ma,为新元古代早期岩浆作用产物。全岩化学组成上,该岩石为准铝质-弱过铝质、钙碱性系列"I"型花岗岩,轻重稀土元素分馏显著,基本无Eu异常,富集Rb,Ba,K,Sr等大离子亲石元素,亏损P,Ti,Nb,Ta等高场强元素。锆石Hf同位素分析结果显示:锆石εHf(t)值为-15.12～-11.52;二阶段模式年龄TDM2=2.46～2.66 Ga。研究表明,奥依库如克岩体形成于板块俯冲消减环境,指示Rodinia超大陆的汇聚。     

新疆塔里木北缘新元古代最晚期岩浆事件

报道了塔里木库鲁克塔格地区新元古代晚期花岗闪长岩和钾长花岗岩的锆石U-Pb年龄和Hf同位素组成。花岗闪长岩锆石U-Pb谐和年龄为630.1±1.3Ma,钾长花岗岩锆石U-Pb谐和年龄为630.6±1.3Ma。Hf同位素组成表明,这2种岩石主要来自古老(中)基性地壳的重熔,可能有部分地幔物质的加入。结合已有的研究表明,650~615Ma期间的岩浆活动代表了塔里木地块新元古代最晚期的岩浆活动,是Rodinia超大陆解体过程中的产物,与泛非造山事件无关。塔里木地块自新元古代中期到早寒武世,持续接受了被动大陆边缘沉积,表明在这一时期塔里木为冈瓦那大陆之外独立的大陆块体,或是位于冈瓦那大陆最边缘的稳定大陆块体。     

马达加斯加Maevatanana金矿区花岗岩锆石U-Pb年龄、Hf同位素特征及其地质意义

马达加斯加中部Maevatanana、Andriamena和Beforona三条绿岩带共有上百处铬、镍、铁、金等金属矿点。对位于马达加斯加中北部绿岩带的Maevatanana西南部花岗岩体进行主量元素、微量元素、锆石LA-MC-ICP-MS U-Pb定年及Lu-Hf同位素分析。岩体主要由黑云母二长花岗岩构成,为准铝质到弱过铝质的高钾钙碱性系列花岗岩,富集Rb、Ba、K等大离子亲石元素(LILE),亏损Nb、Ta、Ti等高场强元素(HFSE),其稀土元素总量为∑REE=92.02×10-6,A/CNK=1.01。其内锆石LA-MCICP-MS U-Pb的年龄为739~767Ma,即中新元古代,其εHf(t)均为负值,揭示该矿区花岗岩体源区为陆壳。其中岩浆锆石和继承锆石的Hf同位素二阶段模式年龄相近,表明花岗岩源岩的形成时期和基底黑云角闪斜长片麻岩的原岩一致。地球化学性质显示花岗岩体为I型花岗岩,与埃达克岩类似。综合数据认为岩体形成于中-新元古代(824~720Ma)Rodinia超大陆裂解,伴随Mozambique洋闭合Tanzanian克拉通与印度Dharwar克拉通汇聚背景下的陆缘弧岩浆活动。     

北大巴山凤凰山岩体锆石U Pb LA ICP MS年龄及其构造意义

北大巴山凤凰山岩体是扬子陆块北缘典型的新元古代侵入岩群,对采自岩体的6个花岗岩(闪长岩)样品进行了LA-ICP-MS锆石U-Pb同位素定年分析。定年数据显示,岩浆活动可分为早期(797±6Ma)、中期(770±6Ma、774±5Ma)、晚期(755±6Ma、750±13Ma和743±6Ma)三个阶段,证实凤凰山岩体为多期岩浆侵入形成。这几期岩浆活动在扬子陆块具同步性和普遍性,广泛被记录在黄陵、汉南等其它新元古代杂岩中。凤凰山花岗岩完整记录了扬子陆块北缘南华纪初期的区域拉张—裂陷事件,其形成可能与导致Rodinia超大陆裂解作用的幕式地幔柱活动有关。本次研究对认识扬子陆块新元古代地壳生长与再造过程及Rodinia超大陆裂解机制具有重要意义。     

云南金平县阿德博独居石矿床成矿时代及地质意义

西南三江地区是我国重要的成矿区带之一,具有复合叠加成矿特征。阿德博独居石矿床位于云南省金平县境内,印度地块、哀牢山-金沙江断裂带南侧,属于哀牢山隆起的东南延伸部分。该矿床赋存于花岗质风化壳中,岩性主要有片麻状花岗岩、二长花岗岩、花岗片麻岩;矿体中主要含有独居石,少量磷钇矿、锆石、金红石、钛铁矿、榍石。岩体中片麻状花岗岩的锆石U-Pb谐和年龄为31.40±0.16Ma(MSWD=7.8),二长花岗岩的锆石U-Pb谐和年龄为34.52±0.22 Ma(MSWD=1.3),表明阿德博岩体形成于新生代古近纪,与三江地区构造体制转换阶段富碱斑岩体的成矿时期一致。片麻状花岗岩中45个锆石Hf同位素数据结果较均一,(~(176)Hf/~(177)Hf)i比值范围为0.282583～0.282712,平均为0.282633,εHf(t=31.40 Ma)范围为-6.00～-1.44,平均值为-4.21。二长花岗岩中13个锆石Hf同位素数据结果变化范围较大,(~(176)Hf/~(177)Hf)i=0.282484～0.282814(平均值为0.282681),εHf(t=31.40 Ma)=-9.43～2.22(平均值为-2.45);其中有8粒锆石的εHf(t)为负值,5颗锆石的εHf(t)为正值,暗示岩体的源区主要为地壳物质的部分熔融,可能有地幔物质的混合。     

粤北大宝山北部九曲岭花岗岩锆石U-Pb年龄和Hf同位素特征

采用LA-MC-ICP-MS锆石U-Pb年龄和Hf同位素测定技术,对大宝山北部九曲岭花岗岩进行测定。结果显示来自九曲岭岩体的三个花岗岩样品的U-Pb谐和年龄分别为169.0±1.9 Ma,171.3±1.4 Ma,450.2±2.9 Ma,表明九曲岭花岗岩体为一复式岩体,主体为燕山期花岗岩,但局部有加里东期花岗岩。锆石Lu-Hf同位素组成测定显示:燕山期岩体的锆石具有低的负εHf(t)值(分别为–12.19~–8.51和–19.47~–8.63),二阶段模式年龄(tDM2)为1.45~1.63 Ga,与华南燕山期花岗岩特征一致,表明其主要是下地壳重熔的产物;加里东期岩体的锆石具有高的εHf(t)值(8.89~12.06),tDM2为0.62~0.78 Ga,表明其源区有新生地壳物质的贡献,暗示早古生代加里东期大宝山区域处于伸展环境。     

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。