滇西新街岩体LA-ICP-MS锆石U-Pb年龄、Hf同位素和地球化学及其构造意义

新街岩体位于昌宁-孟连带北段,主要岩性为二长花岗岩。LA-ICP-MS锆石U-Pb定年结果表明,新街岩体侵位于约82Ma。岩体Si O2含量为74.28%~75.17%,富钾(K2O/Na2O=1.44~1.73)和较低钙Ca O(0.37%~0.41%),铝饱和指数(A/CNK)为1.121~1.156,富集Rb、Th、K、LREE等元素,相对亏损Nb、Ta、Ti、Zr、Hf等高场强元素。这些特征表明,新街岩体属于强过铝质S型花岗岩。新街岩体负且变化范围大的锆石εHf(t)值(-16.9~-0.5)和古老的Hf同位素地壳模式年龄(1.19~2.28Ga),表明其主要来源于古老地壳物质的重熔,并有不同程度的幔源物质加入。由于喜马拉雅新特提斯洋封闭发生在65Ma左右,新街岩体很可能是在喜马拉雅新特提斯洋洋壳俯冲的地球动力学背景下形成的。     

浙江东南印支晚期的构造伸展事件：来自诸暨大爽岩体的证据

出露于浙江省东南部的大爽岩体为黑云母二长花岗岩,LA-ICP-MS锆石U-Pb年代学研究表明该岩体形成于227±2Ma,属印支晚期岩浆作用的产物。地球化学分析显示该岩石低Na2O、富K2O,A/CNK=1.26~1.49(大于1.1),为强过铝质、钾玄质系列花岗岩;岩石稀土总量较高,富Sr(Sr=874.6×10-6~1158×10-6),贫Yb(Yb=3.00×10-6~3.92×10-6),富轻稀土而亏损重稀土,具轻微的负铕异常(δEu=0.68~0.70);相对富集Rb、Th等大离子亲石元素,而亏损Nb、Ta等高场强元素;Sr-Nd同位素分析表明岩石具有较高的初始锶比值(I Sr=0.710718~0.711008)和较低εNd(t)值(εNd(t)=-10.9~-11.1),上述地球化学特征指示该岩体岩浆源区为古老的地壳物质。综合分析认为大爽岩体是古老地壳部分减压熔融的产物,受控于印支造山后的伸展应力作用。     

湖南桂阳大义山南体(太坪山单元)花岗岩形成时代及物质来源探讨

在详细的野外地质调查基础上,本文通过对湖南省桂阳县大义山南体(太坪山单元)黑云母二长花岗岩的岩石化学、锆石U-Pb定年和全岩Sm-Nd同位素以及锆石原位Hf同位素的综合研究,参照前人研究成果,探讨其岩石化学性质、形成时代、物质来源以及形成机制等。LA-ICP-MS锆石U-Pb定年结果显示其n(~(206)Pb)/n(~(238)U)加权平均年龄为153.4±1.1Ma,两颗继承锆石核n(~(207)Pb)/n(~(206)Pb)年龄分别为2449Ma和2498 Ma。岩石高硅、富碱、高钾钙碱性、准铝质到弱过铝质,富集轻稀土元素、部分大离子亲石元素(Rb、K等)和Th、U、Pb等元素,亏损部分高场强元素(Nb、Ta、Ti)和Ba、Sr、P等元素。该岩体zr+Nb+Ce+Y350×10~(-6),10000*Ga/Al2.6,显示出A型花岗岩的特征。全岩Sm-Nd同位素显示ε_(Nd)(t)=-6.94~-5.19,二阶段模式年龄T_(DM2)=1.37~1.51 Ga。锆石原位Hf同位素显示,锆石ε_(Hf)(t)=-9.35~-1.16,T_(DM2)=1.28~1.79 Ga。两颗继承锆石核ε_(Hf)(t)分别为-6.82和1.48。岩石化学和同位素特征表明岩石主要来源于元古代地壳变质杂岩的部分熔融,并可能有少量地幔物质的加入。燕山早期,由于俯冲的古太平洋板块后撤,研究区处于伸展的构造环境,岩石圈减薄,软流圈上涌,导致玄武质岩浆底侵,诱发上覆的古元古代下地壳部分熔融,形成花岗质岩浆,并沿着深大断裂带运移侵位,形成大义山南体(太坪山单元)黑云母二长花岗岩。     

新疆谢米斯台地区乌兰萨拉岩体地球化学、年代学及全岩Sr-Nd和锆石Hf同位素研究

谢米斯台地区位于新疆西准噶尔北部,该地区中酸性岩浆活动强烈。本文对谢米斯台地区乌兰萨拉岩体进行了地质、地球化学、年代学及全岩Sr-Nd和锆石Hf同位素研究。结果表明,乌兰萨拉岩体是一个由碱长花岗岩和花岗闪长岩组成的复式岩体。碱长花岗岩形成时代为晚志留世(422.7±2.0Ma),岩石高硅、富碱,属于准铝质-弱过铝质高钾钙碱性花岗岩;球粒陨石标准化配分模式图显示"V"字型配分样式,Eu负异常强烈,相对富集Ga、K、Rb、Th、U和Pb,亏损Ba、Sr、P、Ti、Cr和Ni等;岩石具有低(~(87)Sr/~(86)Sr)i值(0.7017~0.7038),正的ε_(Nd)(t)值(+4.49~+6.58)和锆石ε_(Hf)(t)值(+10.0~+14.2),Hf同位素模式年龄(t_(DM2))为500~771Ma。花岗闪长岩形成时代为早泥盆世(411.7±1.7Ma),属于准铝质,高钾钙碱性-钾玄岩系列花岗岩;球粒陨石标准化配分模式图显示右倾型配分样式,无明显Eu异常,相对富集LREE、LILE(Rb、Ba、K)、Th、U和Pb,亏损Nb、Ta、P和Ti等;岩石具有低的(~(87)Sr/~(86)Sr)i值(0.7041~0.7046),正的ε_(Nd)(t)值(+1.66~+3.87)和锆石ε_(Hf)(t)值(+4.4~+13.9),Hf同位素模式年龄(t_(DM2))为516~1120Ma,岩石Nd同位素和锆石Hf同位素出现一定程度的解耦。综合研究认为,乌兰萨拉岩体碱长花岗岩属A_2型花岗岩,花岗闪长岩属I型花岗岩,两者都是由新生下地壳发生部分熔融而形成,前者经历了一定程度的分离结晶作用,后者受到亏损玄武质岩浆(俯冲板片脱水交代地幔楔产生的上涌岩浆)的底侵,它们均形成于陆缘弧环境。     

西藏尼木渐新世花岗岩中的岩浆混合作用:对岩石成因及陆壳增生的启示

尼木渐新世黑云母二长花岗岩中含有丰富的形态各异的暗色镁铁质微粒包体。本文报道了寄主岩和镁铁质包体的年代学、元素地球化学及Sr- Nd- Hf同位素组成,据此阐明了岩石的成因,并探讨了岩浆混合作用在成岩中的意义及其对陆壳增生的启示。锆石LA- ICP- MS U- Pb定年结果表明,寄主岩和镁铁质包体的成岩年龄在误差范围内基本一致,均为约30Ma,说明它们同时形成。元素地球化学组成上,寄主黑云母二长花岗岩为高钾钙碱性、准铝质,富集Rb、Th、U等大离子亲石元素,亏损Nb、Ta、Ti、P等高场强元素,且具有高Sr、低Y和Yb含量,Sr/Y比值高,缺乏明显铕负异常,表现出埃达克质岩石的特征。镁铁质包体贫硅,富铁、镁,具有与寄主岩相似的稀土与微量元素分布模式。二者的全岩Sr、Nd同位素和锆石Hf同位素组成也相近\[寄主岩:(87Sr/86Sr)i=0.7057~0.7064,εNd(t)=-1.45~0.35,εHf(t)=1.21~7.34;镁铁质包体:(87Sr/86Sr)i=0.7058~0.7064,εNd(t)=-2.23~-1.57,εHf(t)=2.40~7.04\]。综合分析表明,尼木渐新世黑云母二长花岗岩应主要起源于碰撞加厚的新生镁铁质下地壳的部分熔融,镁铁质包体应为幔源玄武质岩浆与其诱发加厚地壳熔融形成的埃达克质岩浆经不均匀混合作用的产物。结合对冈底斯带岩浆岩已有资料的全面分析,表明幔源玄武质岩浆的底侵及其诱发的岩浆混合作用既是冈底斯岩基形成的主要方式,也是导致青藏高原陆壳增生的重要途径。     

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。     

桂北新寨强过铝质花岗岩的岩石成因及其构造意义——来自年代学、地球化学及Sr-Nd-Hf同位素的制约

LA-ICP-MS锆石U-Pb定年结果显示,桂北新寨花岗岩形成于中奥陶世(465±2Ma)。该花岗岩的地球化学特征表现为化学成分较均一,具有高硅(SiO_2=68.54%~74.57%)、富碱(K_2O+Na_2O=7.61%~8.31%)、更富钾(K_2O/Na_2O=1.77~2.35)、强过铝质(A/CNK=1.09~2.39)和富集大离子亲石元素而亏损高场强元素等特征,属于S型花岗岩。新寨花岗岩具有比较均一的Sr、Nd同位素组成(I_(Sr)=0.71137~0.71328,ε_(Nd)(t)=-7.89~-7.26)。锆石Hf同位素组成为:(~(176)Hf/~(177)Hf)_i=0.28232~0.28252,ε_(Hf)(t)=-6.18~+0.61,Hf同位素两阶段模式年龄TDM2变化于1.67~2.11Ga之间。元素及Nd-Sr-Hf同位素分析结果显示,新寨花岗岩可能源自古元古代地壳变质泥岩的部分熔融,在成岩过程中有少量幔源组分的参与。新寨S型花岗岩可能是广西运动第二幕在桂北地区的岩石学响应,为早古生代构造-岩浆群事件的建立提供了新证据。     

东昆仑早古生代造山后花岗岩的特征——以大干沟花岗岩为例

大干沟花岗岩体位于东昆仑金水口地区,其岩石类型主要为中粗粒正长花岗岩。该花岗岩的SiO_2含量为68.68%~71.12%,平均含量为69.84%;Al_2O_3含量为14.01%~15.40%,平均含量为14.82%;K_2O/Na_2O值高,为1.19~1.64,平均为1.40;铝饱和指数A/CNK值为0.98~1.02,平均为1.00,具有准铝质-弱过铝质花岗岩的特点。岩石稀土元素总量较高,LREE元素富集,具有明显的Eu负异常,相对原始地幔明显富集U、Th,亏损Ti、P、Nb、Ta等高场强元素和Ba、Sr等大离子亲石元素,具有A型花岗岩的特征。花岗岩εNd(t)0,为-5.6~-7.3,tDM=1.54~2.27 Ga,表明其物源可能主要为中元古代物质(金水口群),LA-ICP-MS锆石εHf(t)=-2.2~2.6,显著不同于地壳岩浆的Hf同位素组成,显示有地幔物质添加。LA-ICP-MS锆石U-Pb年龄为392±2 Ma(MSWD=1.14)。结合区域构造演化和上述地球化学特征,认为大干沟岩体为早古生代造山后伸展阶段的产物,是东昆南地体与东昆北地体碰撞后地幔岩浆上涌及地壳熔融的结果。     

新疆西准噶尔庙尔沟岩体的地球化学及年代学研究

新疆西准噶尔庙尔沟岩体侵入于早中石炭世海相火山-沉积建造中,主体由碱长花岗岩组成,局部分布有紫苏花岗岩和碱长花岗岩脉。碱长花岗岩及岩脉高硅、富碱、贫钙,里特曼指数(δ)=2.17~2.98,A/CNK=0.96~1.03,A/NK=1.08~1.13,为准铝质-弱过铝质高钾钙碱性花岗岩,其富集LILEs(Rb、U、K、Th),相对亏损HFSEs(Nb、Ta、P、Ti)和Ba、Sr等,以及强烈Eu负异常,过渡族地幔相容元素Cr、Ni含量低,U、Th、Pb等地壳富集元素含量较高。Sr、Nd同位素组成:(87Sr/86Sr)i=0.70370~0.70541,εNd(t)=+4.10~+6.79,tDM=0.57~0.99Ga。锆石LA-ICP-MS U-Pb定年研究获得锆石U-Pb年龄为309±1.4Ma,表明岩体碱长花岗岩的形成时代为晚石炭世。紫苏花岗岩的SiO 2含量为60.88%~62.06%,Al2O3含量为15.50%~15.72%,里特曼指数(δ)=2.59~2.77,A/CNK=0.86~0.88,A/NK=1.50~1.53,为准铝质钙碱性-高钾钙碱性过渡的花岗岩,相对富集LREE(Rb、U、K、Th),而亏损HREE(Nb、Ta、P、Ti)和Sr,以及较显著的Eu负异常,过渡族地幔相容元素Cr、Ni含量低,U、Th、Pb等地壳富集元素含量较高。Sr、Nd同位素组成:(87Sr/86Sr)i=0.70382~0.70388,εNd(t)=+6.67~+6.98,tDM=0.59~0.62Ga。锆石LA-ICP-MS U-Pb定年研究获得锆石U-Pb年龄为302.1±2.1Ma,表明岩体紫苏花岗岩的形成时代为晚石炭世。综合庙尔沟岩体的地质特征、地球化学特征、年代学和区域地质背景,认为庙尔沟岩体碱长花岗岩及岩脉为A2型花岗岩,紫苏花岗岩具有A型花岗岩的地球化学性质,且它们是可能来自同一个岩浆源区,属于西准噶尔后碰撞阶段的岩浆活动产物。     

新疆西天山呼斯特杂岩体岩石学、锆石U-Pb年龄及Hf同位素特征

呼斯特岩体是新疆西天山博罗科努岛弧带上的一个与矽卡岩成矿有关的复式杂岩体,由二长花岗岩、花岗闪长岩、正长花岗岩、花岗细晶岩、闪长玢岩、辉长岩和中基性包体等组成。本文对该岩体不同岩相岩石开展了岩石学、锆石LAICP-MS U-Pb同位素定年和Hf同位素研究,探讨岩石成因及构造意义。锆石U-Pb定年结果表明,正长花岗岩、闪长玢岩、花岗闪长岩和二长花岗岩加权平均年龄分别为380.2±4.6Ma、372.8±5.9Ma、367.7±4.5Ma和366.2±4.5Ma,岩体侵位时代为晚泥盆世,在大约15Myr期间,至少发生了3~4次岩浆侵入。在地球化学组成上,除辉长岩外,岩体为准铝质-弱过铝质、高钾钙碱性-低钾(拉斑)系列的I型花岗岩,轻重稀土分馏明显,具Eu负异常;富集Th、U,亏损Ba、P和高场强元素(如Nb、Ta、Zr、Ti),为晚古生代北天山洋向南俯冲于伊犁地块背景下岩浆活动的产物。二长花岗岩锆石Hf同位素组成较为均一,εHf(t)值为1.3~3.0,二阶段Hf模式年龄为1171~1280Ma,远大于成岩年龄,说明原始岩浆从地幔分异后经历了较长时间的地壳滞留。研究认为,高钾中酸性岩(花岗岩、闪长玢岩和中基性包体)由元古代新生基性下地壳部分熔融而成,伴有受俯冲沉积物熔体交代的幔源岩浆混合。低钾花岗闪长岩高Sr、低Y和Yb,属O型埃达克岩,与同源的辉长岩一起由俯冲的大洋板片部分熔融形成,源岩为低钾的拉斑玄武岩。     

以改革为动力以创新求发展--机械工业第六设计研究院“三项制度”改革纪略

机械工业第六设计研究院原隶属于机械工业部,为事业单位,2000年10月转制后隶属于中国机械装备(集团)公司,为企业单位。该院现有在职员工459人,外聘人员300人,离退休人员356人,其中,中国工程院院士1人,中国工程设计大师2人,教授级高级工程师50人,高级工程师近260人,工程师300多人。该院是工业和民用建筑设计双甲级单位,并具有甲级工程总承包和工程监理资质。建院五十多年来,该院先后完成了5000余项大中型工业和民用建筑项目的设计和咨询,为我国国民经济建设和发展做出了卓越贡献。     

Tungsten-bearing baotite from Pierrefitte,Pyrenees, France

Summary Baotite occurs in the Garaoulére orebody, at Pierreftte, France, as an accessory mineral, included in alstonite and celsian, and associated with sphalerite, galena, pyrite, siderite and calcite in hydrothermal veins crosscutting calcareous, rutile-bearing, siltstones. Microprobe analyses revealed high W0₃ concentrations (up to 6 wt.%) in baotite. The empirical formula of W-rich baotite is Ba_3.959Ti₄(Ti_3.169W_0.393Fe_0.116Al_0.073 Cr_0.048Nb_0.024)_3.823 Si_4.05O₂₈Cl_1.166. The excess of charges due to the presence of W⁶⁺ and Nb⁵⁺ is compensated by the introduction of M³⁺ (Fe, Al, Cr) into Ti-octahedra, by the appearance of Al in Si-tetrahedra (for W-poor baotite) and by the appearance of vacancies in Ti-octahedra (3Ti⁴ -> 2W⁶⁺ + and in Ba-sites (Ti⁴⁺ Ba²⁺ W⁶⁺, ). The unit-cell parameters of W-rich baotite are: a = 19.92(2), c = 5.930(8) Å. Niobium-rich baotites (Baiyun-Obo,Semenov et al., 1961; Karlstein,Nmec, 1987) are characterized by substitutions: Ti⁴⁺(VI), Si⁴⁺(IV)Nb⁵⁺(VI), Al³⁺(IV) and 2Ti⁴⁺, Ba²⁺ 2Nb⁵⁺, .

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Wolfram führender Baotit von Pierrefitte, Pyrenäen, Frankreich

Zusammenfassung Baotit kommt in dem Garaoulére Erzkórper in Pierrefitte, Frankreich als ein akzessorisches Mineral in Einschlÿussen in Alstonit und Celsian vor. Er ist mit Zinkblende, Bleiglanz, Pyrit, Siderit und Calcit assoziiert. Diese Paragenese ist an hydrothermale Gänge gebunden, die kalkige rutil-führende Siltsteine durchsetzen. Mikrosondenanalysen zeigen hohe W0₃ Gehalte (bis zu 6 Gew.%) in Baotit. Die empirische Formel von wolfram-reichem Baotit ist: Ba_3.959Ti₄(Ti_3.169W_0.393Fe_0.116Al_0.073Cr_0.048Nb_0.024)_3.823 Si_4.05O₂₈Cl_1.66. Der durch die Anwesenheit von W⁶⁺ und Nb⁵⁺ erforderliche Ladungsausgleich ergibt sich durch das Eintreten von M³⁺ (Fe, Al; Cr) in Ti-Oktaeder, und von Al in Si-Tetraeder (für W-armen Baotit) und schließlich durch das Erscheinen von Leerstellen in Ti-Oktaedern (3Ti⁴⁺ 2W6+ + und in Ba-Stellen (Ti⁴⁺, Ba` W⁶⁺, Die Zellparameter von ldW-reichem Baotit sind: a = 19.92(2), c = 5.930(8) Å. Niob-reiche Baotite (Baiyun-Obo, Semenov et al., 1961; Karlstein, Nmec, 1987) sind durch Substitutionen charakterisiert: Ti⁴⁺(VI), Si⁴⁺(IV)Nb⁵⁺(VI), Al³⁺(IV) und 2Ti⁴⁺, Ba²⁺ 2Nb⁵⁺, .

     

我国云南江城氯氧镁铝石的研究

氯氧镁铝石(Koenenite)是一种少见矿物,最初发现于德国Gttingen。后来,F.里勒(F.Rinne)、R.库恩(R.Kühn)、H.-H.洛斯(H.-H.Lohse)、R.奥勒曼)R.Allmann)等人先后都作过报导,而在我国还是首次发现。氯氧镁铝石结构比较特殊,性质上是一个多变的矿物。     

设计源于构思--谈草图设计大师SketchUp

CAAD(Computer Aided Architectural Design)在建筑设计专业工作中的应用技术称为计算机辅助建筑设计技术，它从上世纪60年代兴起80年代走红90年代席卷了整个建筑市场，并迅速成熟。设计师无疑已经离不开它们，代表作品有广为人知的AutoCAD、3DMAX，然而建筑师在享用它们的同时却不停的感慨它们的局限性：“它们把建筑设计引向机械的、单调的缺乏个性的死胡同……”，“建筑设计本身是一种模糊性设计，前期并不需要严格的定性定量，而且，美学问题是无法用定量的方法来描述的……”，它的呆板复杂与建筑师的灵性脱缰的思维无法合谐的同行，两者徘徊于等待与被等待之间隔岸对视。     

Leucitites from Gaussberg,Antarctica

Leucitities of probable late Pleistocene age from the extinct volcano of Gaussberg on the coast of East Antarctica consist of microphenocrysts of olivine, diopside, and leucite in a largely glassy groundmass. Their extreme K contents and K/Na ratios, as well as high Rb, Ba, and possibly Ti, are compatible with an origin by small degrees of partial melting of phlogopite-rich mantle below the level of amphibole stability, whereas their enrichment in P, Sr, Zr, Nb, La, Ce, Pb, and Th indicates the presence of minor phases such as apatite in the source material. Although the Mg/(Mg+Fe) values (0.70) and relatively high Ni and Cr contents suggest that the Gaussberg lavas represent near-primary melts, some degree of fractionation involving an aluminous phase (probably garnet) may be necessary to produce liquids with atomic K>Al. Alternatively, an as yet poorly understood process such as wall-rock reaction, liquid immiscibility, or mantle metasomatism may have been a critical factor in the genesis of these unusual rocks.Gaussberg is situated on a passive continental margin and does not appear to be related to any other known area of Cainozoic volcanic activity.     

Metamorphic P-T paths from calcic pelitic schists from the Strafford Dome, Vermont, USA

Metamorphism of the Gile Mountain Formation and Waits River Formation in the Strafford Dome and Townshend-Brownington Syncline in east-central Vermont records two nappe-style events, D1 and D2, followed by doming. D1 formed a muscovite + biotite ± ilmenite schistosity subparallel to compositional layering, SO, and was followed by heating to garnet grade. The temperature and pressure at the end of D1 are estimated to be c . 450 C and 6-8 kbar. D2 variably crenulated and folded S1 during a nearly isothermal pressure increase of 1-2 kbar, calculated from compositions of garnet, which have inclusions trails with progressive crenulation and rotation of the S1 fabric. Similar P-T paths are computed for most of the area, suggesting that the later schistosity developed during emplacement of a regional nappe 3-6 km thick. There is a general lack of D3 (dome-stage) microstructures.
Near the Strafford-Willoughby Arch, staurolite and kyanite overgrew S2 in pelites, and plagioclase with increasing X _An overgrew S2 in calcic pelites, reflecting post-D2 heating to a maximum of 550-600 C. Metamorphic pressures at the end of D2 are fairly constant on the west side of the dome, indicating minor dome-stage uplift. In contrast, pressures at the thermal peak of metamorphism decrease by more than 4 kbar east of the dome. The observed pattern of isotherms and isobars is mainly the result of post-metamorphic, differential uplift and unroofing.
Finally, a minor, retrograde metamorphism produced the assemblage albite + epidote + K-feldspar + muscovite + chlorite, with grade increasing east toward the Connecticut River.     

Late Quaternary mollusks from glacial Lake Algonquin,Nipissing, and transitional sediments from southwestern Ontario,Canada

Mollusks were studied from six sites in Lake Algonquin deposits (12,000-10,000 yr B.P.), five transitional (Lake Stanley low stage; 10,000 – 6000 yr B.P.), and six Nipissing stage sites (6000-4000 yr B.P.) east of Lake Huron in southwestern Ontario. The sites represent a variety of near-shore, lagoonal, estuarine, and fluvial environments. Eighteen species were limited to occurrences in Algonquin stage deposits; 8 were found only in the transitional age sites; and 14 species were restricted to Nipissing stage localities. With the possible exception of Goniobasis livescens, which occurred at five of the six Nipissing stage sites, the remaining stratigraphically limited species were usually restricted to one or two localities and probably cannot be used as zone fossils. Some cold-tolerant species (e.g., Anodonta grandis simpsoniana) were very early migrants into the study area, while others arrived later, apparently from eastern, southern, and western sources. Mollusks proved useful in paleoenvironmental reconstructions and to a lesser extent in biostratigraphic zonation.     

Hazard and risk from large landslides from Mount Meager volcano,British Columbia,Canada

During the past 8000 years, large volcanic debris flows from Mount Meager, a Quaternary volcano in southwest British Columbia, have reached several tens of kilometres downstream in Lillooet River valley, with flow velocities of many metres per second and flow depths of several metres. These debris flows inundated areas that have become settled in the past 100 years and are now experiencing rapid urban growth. Notably, Pemberton, 65 km from Mount Meager, has doubled in size in the past five years. Approval of subdivision and building permits in Pemberton and adjacent areas requires assessment and mitigation of flood hazards, but large, rare debris flows from Mount Meager are not considered in the permitting process. Unlike floods, some volcanic debris flows occur without warning. We quantify the risk to residents in Lillooet River valley from non-eruption triggered volcanic debris flows based on Holocene landslide activity at Mount Meager. The calculated risk exceeds, by orders of magnitude, risk tolerance thresholds developed in Hong Kong, Australia, England, and in one jurisdiction in Canada. This finding poses a challenge for local governments responsible for public safety.