辽北抚顺-清原地区太古宙基底地球化学组成特征及其地质意义

最近的研究表明,辽北抚顺、清原地区太古宙基底主体形成于新太古代,不存在广泛分布的中太古代地质体。表壳岩系以不同规模分布于TTG花岗质岩石中,主要由斜长角闪岩、角闪变粒岩、黑云变粒岩及少量片麻岩组成。本文对该区新太古代表壳岩系和TTG花岗质岩石进行了地球化学研究。小莱河斜长角闪岩具近于平坦型的稀土模式[(La／Yb)n=1.0],大离子亲石元素富集。存在3种类型角闪变粒岩。类型1角闪变粒岩具平坦型稀土模式[(La／Yb)n=1．1～2．93,大离子亲石元素富集,其特征与共生的斜长角闪岩十分相似。类型2角闪变粒岩常量元素组成与类型1角闪变粒岩类似,但轻稀土富集[(La／Yb)n=11．4～20．2],与之存在较明显区别。类型3角闪变粒岩轻重稀土强烈分离[(La／Yb)n=41．83。黑云变粒岩稀土模式和微量元素组成与类型2角闪变粒岩相似,但显示出更为富集的组成特征。TTG花岗质岩石构成辽北太古宙基底的主体。它们轻重稀土强烈分离[(La／Yb)n=25．8～194．4],无明显负铕异常(Eu／Eu^*=0．75～1．35)。研究表明,辽北地区太古宙基底表壳岩系变质原岩主体为拉斑玄武岩、安山岩、英安岩及相应火山碎屑沉积岩,表壳岩系和TTG花岗质岩石形成于板块汇聚的岛弧环境。它们构成了华北克拉通新太古代吉(吉林)-辽(辽宁)-冀(河北)(弧陆碰撞增生型)造山带的重要组成部分。     

鲁西莲花山地区新太古代晚期二长花岗岩中的表壳岩包体——SHRIMP锆石U-Pb定年和地球化学特征

为了确定鲁西莲花山地区新太古代晚期二长花岗岩中的表壳岩包体的形成时代，并探讨与相邻雁翎关地区的雁翎关岩组中的新太古代早期变质火山岩系的关系。本文对表壳岩包体及相关岩石进行了锆石年代学和地球化学研究。表壳岩包体主要由变质超基性岩和斜长角闪岩组成，另含少量（黑云）角闪变粒岩和黑云变粒岩。SHRIMP锆石U-Pb定年结果显示：角闪变粒岩的岩浆锆石年龄为2 757 Ma；侵入斜长角闪岩的奥长花岗岩脉的年龄为2 593 Ma；从变质超基性岩分选出很少锆石，它们普遍遭受强烈变质重结晶，²⁰⁷Pb/²⁰⁶Pb年龄为2 657~2 397 Ma。变质超基性岩具轻稀土亏损型或平坦型稀土模式，斜长角闪岩具平坦型稀土模式，角闪变粒岩具轻稀土略富集稀土模式，虽然大离子亲石元素相对富集，但都无明显Nb、Ta亏损。表壳岩包体的岩石组合、地球化学组成特征和形成时代可与相邻雁翎关地区的雁翎关岩组中的新太古代早期变质火山岩系对比，形成于大洋环境。新太古代早期表壳岩的原有分布范围应比现在所见到的更为广泛。     

西天山尼勒克一带大哈拉军山组火山岩地球化学特征及构造意义

对西天山尼勒克一带大哈拉军山组流纹岩类研究表明,岩石具富硅(SiO_2=70.78%~76.85%)、富铝(Al_2O_3=11.05%~15.54%)、富碱(K_2O+Na_2O=7.87%~9.71%)、贫钙(CaO=0.16%~1.42%)、低钛(TiO_2=0.08%~0.41%)特征,属钙碱性低钛流纹岩类。稀土元素总量较低(∑REE=50.77×10~(-6)~88.77×10~(-6)),稀土分布模式为轻稀土富集右倾型,铕负异常明显(δEu=0.59~0.81),相对富集Rb,Th,K等大离子亲石元素,亏损Nb,Ta,Ti等高场强元素,具较高的Rb/Sr、Nb/Ta和Th/Ta比值和较低的Ti/Zr、Ti/Y及Ta/Yb比值,表明其可能为上地壳部分熔融产物,同时具大陆边缘弧亲缘性。结合区域构造演化,认为伊犁地块北缘早石炭世处于大陆边缘弧环境。     

新疆博格达东缘色皮口地区晚石炭世裂谷火山岩地球化学、锆石U-Pb年代学及Hf同位素研究

新疆色皮口地区位于博格达造山带东段北部,区域内的上石炭统柳树沟组火山岩为玄武岩-玄武安山岩、角斑岩-石英角斑岩和流纹岩,组成双峰式火山岩建造。岩石SiO 2含量为48.07%~77.62%,赖特碱度率(AR)为1.35~4.7,Na2O+K2O含量为3.74%~9.02%,K2O/Na2O值为0.04~1.04,为低钾高钠钙碱性-碱性岩石。玄武岩、玄武安山岩TiO 2=0.86%~1.7%,较高的Al、低Mg,以及低K2O/TiO 2和K2O/P2O5比值(分别为0.13~1.81、0.36~6.00),反映了在岩浆演化过程中发生了不明显的分离结晶作用。玄武岩、玄武安山岩、角斑岩不相容元素K、Rb、Th、Ba强富集,高场强元素Nb、Ta、Zr、Hf无富集,Ti亏损不明显,玄武岩(Th/Nb)N值为1.36~6.55,Nb/La值为0.29~0.44,具有较低的Nb/Zr比值(0.03~0.05)。由玄武岩到石英角斑岩,稀土元素组成略右倾平行曲线簇,倾斜度(轻重稀土分异度)略增大,铕负异常趋于明显(δEu=0.81~1.17)。流纹岩不相容元素K、Rb、Th、Ba富集,高场强元素Nb、Ta、Zr、Hf富集,流纹岩稀土总量增高,轻重稀土分异增大,明显铕负异常(δEu=0.27~0.50),显示后期较强的岩浆分异作用。石英角斑岩的锆石LA-ICP-MS U-Pb定年结果为314.9±1.2Ma(n=16,MSWD=0.4,Th/U比值在0.56~1.21之间),这表明石英角斑岩形成时代为晚石炭世。石英角斑岩中锆石的176Hf/177Hf比值均分布在0.282897~0.283097之间,并具有较高的正εHf值(11~18),平均值为14,Hf的模式年龄tDM2介于180~628Ma。所有锆石的176Hf/177Hf比值和εHf值位于亏损地幔演化线与下地壳之间,并靠近亏损地幔演化线。上述特点反映晚石炭世火山岩形成于板内裂谷环境,下部玄武岩与角斑岩-石英角斑岩具有同源特征,暗示岩浆源区来源于亏损地幔,并受地壳混染。     

内蒙古狼山地区早石炭世角闪辉长岩、花岗闪长岩的岩石成因及构造意义

内蒙古狼山山脉西侧分布有大面积的晚古生代岩浆岩,时代集中在早石炭世—晚二叠世,早石炭世角闪辉长岩、花岗闪长岩体出露于潮格温都尔镇西侧。角闪辉长岩体呈岩滴状产出,被花岗闪长岩体侵入,LA-ICP-MS锆石U-Pb年龄显示,角闪辉长岩的~(206)Pb/~(238)U加权平均年龄为329.0±2.3 Ma,花岗闪长岩的~(206)Pb/~(238)U加权平均年龄为331.1±0.9 Ma~330.0±4.2 Ma。花岗闪长岩暗色矿物以角闪石为主,富钠(Na2O=3.48%~4.46%),高钠钾比值(Na2O/K2O=1.03~2.39),钙碱性系列,P2O5-SiO_2之间存在较好的负相关性,岩石地球化学特征具Ⅰ型花岗岩的特点。Hf同位素及元素地球化学特征指示了角闪辉长岩及花岗闪长岩均来自于受地壳混染的亏损地幔,为同源岩浆演化的产物。角闪辉长岩及花岗闪长岩稀土元素配分型式一致,均为轻稀土元素富集,重稀土元素亏损,具弱的负Eu异常;角闪辉长岩富集Ba、Sr,亏损Nb、Ta、Zr、Hf;花岗闪长岩富集大离子亲石元素Rb、K、Pb、Sr,不同程度地亏损高场强元素Nb、Ta、P、Ti,总体反映了岩浆弧的地球化学特征。结合区域地质背景,早石炭世狼山地区侵入岩岩石组合为角闪辉长岩(闪长岩)+石英闪长岩+花岗闪长岩,认为狼山地区早石炭世处于大陆边缘弧构造背景。     

华北克拉通新太古代板块俯冲作用:来自山西云中山地区变质高镁火成岩组合的证据

在华北克拉通中部的山西云中山地区,新太古代花岗闪长质片麻岩中存在一些超镁铁质岩-镁铁质岩块及由斜长角闪岩、角闪变粒岩、石英岩和石榴夕线黑云片岩等岩石类型构成的变质表壳岩残片,其中的超镁铁质-镁铁质岩、斜长角闪岩和角闪变粒岩构成一套高镁火成岩组合。超镁铁质岩已变质为橄榄绿泥阳起片岩等岩石类型,呈变余斑状结构,橄榄石斑晶仍有保存;岩石SiO_2含量为39.22%～44.99%,Al_2O_3为8.82%～13.47%,Mg O为19.24%～22.13%,Na_2O+K_2O=0.71%～1.11%,CaO为5.75%～8.42%;Al_2O_3/TiO_2=14.8～17.4,CaO/Al_2O_3=0.60～0.84;化学成分上与科马提岩有一定的相似性。与之紧密伴生的斜长角闪岩也具有高镁特征,Mg O含量为11.28%～15.09%,铝、硅和碱质均偏低,具正铕异常,显示堆晶辉长岩的特征。非高镁斜长角闪岩有相对高的铝、硅和碱质,其原岩应为钙碱性玄武岩。角闪变粒岩样品的SiO_2含量为54.21%～55.71%,Al_2O_3为14.24%～15.49%,Mg O为6.26%～8.28%,Fe OT/Mg O=1.11～1.58,高钠低钾,Na_2O+K_2O=3.7%～4.78%,Na_2O/K_2O=5.15%～13.13,Mg#=53.0～61.5,属于高镁安山岩。由超镁铁质质岩-斜长角闪岩-角闪变粒岩构成的变质高镁火山岩组合具有钙碱性系列趋势。超镁铁质岩稀土元素含量总量较低,具有轻稀土富集和重稀土亏损的稀土型式;斜长角闪岩与超镁铁质岩比较,除富集大离子亲石元素和Cr、Ni明显较低外,具有相似的微量元素图谱形态。三种岩石类型在微量元素蛛网图上均显示出Ta、Nb、Ti负异常和Pb正异常。野外产状和岩石地球化学特征表明超镁铁质岩和高镁斜长角闪岩属于阿拉斯加型杂岩体,角闪变粒岩属于赞岐岩质高镁安山岩。在Zr/Nb-Nb/Th和Nb/Y-Zr/Y构造环境判别图解上显示出与俯冲相关的演化趋势,在Hf-Th-Ta、Nb/La-(La/Sm)N和Th/Yb-Nb/Yb图解上也落在岛弧钙碱性岩石区域。以上特征表明高镁火成岩组合形成于与板块俯冲相关的岛弧构造背景。野外地质关系和锆石U-Pb年龄限定高镁火成岩组合形成时代在～2.5Ga。云中山地区阿拉斯加型镁铁质-超镁铁质杂岩与赞岐岩质高镁安山岩共生,表明该地区存在新太古代的板块俯冲作用,为太古宙存在板块构造机制提供了新证据。     

北阿尔金蛇绿混杂岩带中斜长花岗岩的成因及其地质意义

北阿尔金蛇绿混杂岩带恰什坎萨依剖面南端的斜长花岗岩,呈不规则脉状和透镜状产出于蚀变辉绿岩之中。该斜长花岗岩具有高的SiO2含量(70.42%~78.29%),Al2O3含量低(9.51%~11.75%),高Na2O低K2O,K2O/Na2O=0.02~0.09,属于低钾准铝质岩石;其∑REE偏低(80.15×10-6~104.1×10-6),具中等Eu异常(δEu=0.68~0.73)以及轻稀土轻微富集的特点,微量元素显示相对富集Th、U而亏损Nb、Ta、Ti的特征。以上特征与产于蛇绿岩中的斜长花岗岩的基本特征相符合。蚀变辉绿岩主量元素显示低SiO2、Al2O3、K2O、TiO2,高CaO、Na2O以及富集Th、U、La、Ce,相对亏损Nb、P、Ti的特征,部分蚀变辉绿岩样品SiO2、Na2O含量的升高应与岩石遭受海水蚀变有关。稀土元素显示弱的Eu异常(δEu=0.86~0.94)以及轻稀土轻微富集的特点。蚀变辉绿岩Mg#=51.3~54.8,Ti/V=11~22,La/Nb=1.67~2.07,Zr/Nb=10.3~27.1的特点与区内蛇绿岩地球化学特征一致,应为区内蛇绿岩的组成部分。斜长花岗岩LA-ICP-MS锆石U-Pb年龄为518.5±4.1Ma,Hf同位素εHf(t)=4.25~9.90。在La-SiO2及TiO2-SiO2图解上,斜长花岗岩均显示部分熔融成因,结合岩石非常低Sr高Yb的特点,认为其应形成于洋壳在运移过程中发生的部分熔融。全岩Sr、Nd、Pb同位素显示蛇绿岩源区具有EMII型富集地幔特征,与前人对区内洋中脊型玄武岩的同位素研究具有一致性,而洋壳源区富集地幔特征暗示此时的洋壳形成于洋盆裂解的早期。结合以上资料分析,本次研究的斜长花岗岩和蚀变辉绿岩可能形成于北阿尔金有限洋盆裂解的早期,形成时代为518.5±4.1Ma。     

辽吉地区含硼岩系中斜长角闪岩地球化学

辽吉地区古元古界含硼岩系经过了中高级区域变质和混合岩化作用,主要由黑云母变粒岩、浅粒岩、电气石变粒岩、斜长角闪岩及富镁质含矿岩石组成,局部形成层状混合花岗岩。斜长角闪岩在含硼岩系内各个岩组中都有分布,岩石化学分析显示斜长角闪岩具有富钠、富镁、高铁、高钛特征,MgO含量成多众数值分布,辽东地区斜长角闪岩MgO含量高于集安地区,并且各类斜长角闪岩中硼含量都较高。辽东地区B、Cr、Ni明显高于集安地区,显示为海相地幔岩浆岩特征更为明显,集安地区则显示为变质热液改造特征。辽东地区斜长角闪岩的稀土地化显示为热液改造的幔源岩浆特征,集安地区的斜长角闪岩的稀土地化显示为壳源沉积岩特征。含硼岩系斜长角闪岩与浅粒岩稀土配分模式相似,表明部分斜长角闪岩与浅粒岩具有岩浆成因特征,而电气变粒岩、黑云变粒岩与混合岩稀土富集模式显示海相沉积泥岩变质成因,混合岩化及变质热液对原岩具有明显改造作用。斜长角闪岩石的地球化学特征表明原岩环境为富钠、富硼的海相环境,原岩主要是海相富镁拉斑玄武岩和海相泥质岩。     

长白山新生代火山岩之下新太古代基底年代学及地球化学特征

对长白山第四系玄武岩覆盖区零星出露的花岗质岩石和片麻岩进行LA-ICPMS锆石U-Pb年龄测定及地球化学分析,结果显示花岗质岩石的年龄为2 509~2 558 Ma;斜长角闪片麻岩的年龄为2 475~2 553 Ma。地球化学特征上,这些岩石均属奥长花岗岩-英云闪长岩-石英闪长岩系列(TTG),稀土元素配分模式图呈右倾型,轻重稀土元素分馏明显(LREE/HREE=3.85~34.48),白云母二长花岗岩具有铕的负异常(δEu=0.41~0.54),富集Rb、K、Th等元素,亏损Nb、Sr、P、Ti等元素;黑云斜长角闪石片麻岩具有铕负异常(δEu=0.67~0.76),富集Rb、K、La、Nd等元素,亏损Th、Nb、Sr、P、Yb等元素;花岗质片麻岩和黑云斜长片麻岩具有铕的弱负-正异常(δEu=0.87~3.3),富集Rb、K、Sr等元素,亏损Nb、Th、P等元素。年代学和地球化学特征与白山地块和和龙地块中的同类岩石基本一致,表明白山地块与和龙地块在晚太古代是同一个陆块(龙岗陆块),二者目前的分布格局是后期北东向左行断裂构造改造的结果。     

冀东滦县地区前震旦纪铁矿与火山喷发沉积旋回的关系

滦县地区包括滦县、滦南、抚宁、卢龙一带,是冀东前震旦纪铁矿的重要成矿区之一。本区铁矿属变粒岩~闪石型磁铁石英岩,该类铁矿多呈层状或似层状,规模较大,以大中型矿床为主。区内晚太古代滦县群(原称单塔子群)地层分布广泛,该群自下而上可分为五组:①架炮山组(Ar_2j):上部主要为角闪变粒岩,夹黑云变粒岩,石榴角闪变粒岩等;下部以角闪斜长片麻岩、斜长角闪岩为主,夹黑云变粒岩、浅粒岩等薄层,偶见磁铁石英岩小透镜体。②阳山组(Ar_2):由含角闪黑云变粒岩、角闪变粒岩组成,夹斜长角闪岩、偶夹石榴     

Police, politics, and the right to the city

Space and spatiality have recently been at the core of debates concerning the political possibilities of the city. The arguments advanced in this paper might be seen as an attempt to contribute to these debates through a reflection on the spatiality of (in) justice, politics, and the right to the city. The case of French urban policy, with its focus on distressed urban areas, and the `suburban problem' in France are used as examples to make arguments more concrete.     

Metals,arsenic, and sulfur in the Aue and Eibenstock granites,Erzgebirge

Average concentrations of Pb, Zn, Cu, and other metals, as well as S and As, were calculated for the Aue granitic cupola, the contact aureole of which hosts the large vein-type uranium deposit of Schlema-Alberoda and the Schneeberg uranium-base metal deposit (Erzgebirge, Germany). The cupola was exposed by mine workings and boreholes, which provided an opportunity to evaluate variations in the abundances of metals in the granites over a vertical interval of more than 2.5 km and estimate their losses in the upper oxidized part of the investigated volume of the cupola (coefficient of iron oxidation, KO _Fe, increases in the granites from bottom to top from 7 to 70%) compared with the lower unaltered and unoxidized part (with a KO _Fe plateau at about 5%). The average concentrations of metals in the upper part of the cupola are lower than those in the lower part by a factor of 2.5 for Pb, 1.56 for Zn, 1.45 for Cu, 1.3 for Co, etc. A similar decrease in the abundances of ore elements along the vertical section associating with the relative epigenetic alteration and oxidation of the granite was previously described by us for U and Th and for the components of high-temperature ores, W, Sn, and Mo. The removal of ore elements from the granite was accompanied by a decrease in the bulk contents of sulfur and arsenic by a factor of 1.35 and 1.65, respectively. The leaching of trace metals from the granites of the upper part of the Aue cupola was followed by their partial redeposition above the cupola in the ore veins of the Schlema and Schneeberg deposits. Original Russian Text ? Vikt. L. Barsukov, N.T. Sokolova, O.M. Ivanitskii, 2006, published in Geokhimiya, 2006, No. 9, pp. 967–982.     

Text, talk, things, and the subpolitics of performing place

This article tells the story of how a group of Dutch and Belgian citizens organized themselves to promote an area that they valued, to put it on the map, to raise awareness about its qualities, and to protect it from urban and industrial development. Our theoretical perspective focuses on the performative and political aspects of this place-making process and the discursive and material practices involved. We connect this to Beck’s concept of subpolitics.Our findings show how the group performed this place not only through text and talk - giving the area a name, using their knowledge and expertise to raise awareness about its values, lobbying and cooperating with decision-makers -, but also through things - installing art objects and information signs that articulate certain characteristics and values of the area. Our findings demonstrate the struggles involved in these performances. The group involved multiple perspectives on what the important values and characteristics of the area are and on what strategies would work best in trying to influence decision-making and protect the area. However, the use of expertise as the main strategy to gain influence excluded the more critical and activist strategies and privileging archaeological and historical values and characteristics came at the expense of attention on agricultural and natural values.Our findings make clear that performing place cannot be taken to be homogeneous and that it inevitably involves multiple perspectives and demands. The struggles, power relations and dynamics of inclusion and exclusion that this multiplicity implicates reveal a form of sub-politics that involves both politicization and depoliticization. Also, it is a form of subpolitics that is more diverse and ambiguous than Beck’s conceptualization presupposes by its emphasis on the role of outsiders as a homogeneous group.     

Total mercury and monomethylmercury in water, sediments, and hydrophytes from the rivers, estuary, and bay along the Bohai Sea coast, northeastern China

Mercury contamination in aquatic environments is of worldwide concern because of its high biomagnification factor in food chains and long-range transport. The rivers, estuary and the bay along the northwestern Bohai Sea coast, northeastern China have been heavily contaminated by Hg due to long-term Zn smelting and chlor-alkali production. This work investigated the distributions of total Hg (THg) and monomethylmercury (MMHg) in the water, sediment and hydrophytes from this area. Concentrations of THg in sediment (0.5–64 mg kg⁻¹) and water (39–2700 ng L⁻¹) were elevated by 1–3 orders of magnitude compared to background concentrations, which induced high concentrations of MMHg in these media. The highest concentration of MMHg in sediment reached 35 μg kg⁻¹, which was comparable to that in the Hg mining area, Wanshan, China, and the highest MMHg concentration of 3.0 ng L⁻¹ in the water sample exceeded the MMHg Chinese drinking water guideline of 1.0 ng L⁻¹. Concentrations of THg in a sediment profile from Jinzhou Bay were found to be consistent with annual Hg emission flux from a local Zn smelter (r = 0.74, p < 0.01), indicating that Hg contamination was mainly caused by Zn smelting locally. For some freshwater hydrophytes, concentrations of THg and MMHg ranged from 5.2 to 100 μg kg⁻¹ and 0.15 to 12 μg kg⁻¹, respectively. Compared to sediment, concentrations of THg in hydrophytes were 2–3 orders of magnitude lower but MMHg was comparable or higher, indicating that the bioaccumulation in plants was distinct for the two Hg species studied. The data suggest that a significant load of Hg has been released into the northwestern coastal region of the Bohai Sea.     

Distribution of REE,LILE, and HFSE between biotite,feldspar, and the melt in the granulite facies migmatite,nimnyr block,Aldan shield

The behavior of trace elements under conditions of partial melting of granitoid rocks has been studied. The element’s partition coefficients between minerals and the melt D_i^min/melt depends, in the first place, on the composition of the primary melt. In biotite the HREE D_i are a little below 1, while those of LREE, especially D_i for Ce, are 1–3 orders of magnitude less. This leads to an efficient differentiation of REEs in anatexic melts especially when biotite is the main mineral phase of restite. On the contrary, there are feldspars, the D_i of which cannot provide such a magnitude of differentiation. Unlike garnets and pyroxenes, whose stability in restite permits enrichment of anatexic melts produced in migmatization zones with Nb, Ti, and Cr, the presence of biotite in restite causes depletion of melts with those elements as well as with Rb. Feldspars, under conditions of their fractional crystallization or during differentiation of an anatexic melt, deplete the latter with Sr, Ba, and Rb, but enrich it with Nb, Ti, Cr, Y, Zr, and V.     

Dielectric constants of apatite,epidote, vesuvianite,and zoisite,and the oxide additivity rule

The dielectric constants and dielectric loss values of 4 Ca-containing minerals were determined at 1 MHz using a two-terminal method and empirically determined edge corrections. The results are: vesuvianitel κ′ _a=9.93 tan δ=0.006 κ′ _c=9.79 tan δ=0.005 vesuvianitel κ′ _a=10.02 tan δ=0.002 κ′ _c=9.85 tan δ=0.003 zoisite1 κ′ _a =10.49 tan δ=0.0006 κ′ _b =15.31 tan δ=0.0008 κ′ _c=9.51 tan δ=0.0008 zoisite2 κ′ _a =10.55 tan δ=0.0011 κ′ _b =15.45 tan δ=0.0013 κ′ _c=9.39 tan δ=0.0008 epidote κ′ ₁₁= 9.52 tan δ=0.0008 κ′ ₂₂=17.1 tan δ=0.0009 κ′ ₃₃= 9.37 tan δ=0.0006 fluorapatite1 κ′ _a =10.48 tan δ=0.0008 κ′ _c = 8.72 tan δ=0.0114 fluorapatite2 κ′ _a =10.40 tan δ=0.0010 κ′ _c=8.26 tan δ=0.0178 The deviation (δ) between measured dielectric polarizabilities as determined from the Clausius-Mosotti equation and those calculated from the sum of oxide polarizabilities according to α _D (mineral)=∑ α _D (oxides) for vesuvianite is ～ 0.5%. The large deviations of epidote and zoisite from the additivity rule with Δ=+ 10.1 and + 11.7%, respectively, are attributed to “rattling” Ca ions. The combined effects of both a large F thermal parameter and possible F-ion conductivity in fluorapatite are believed to be responsible for Δ=+2–3%. Although variation of oxygen polarizability with oxygen molar volume (V_o) is believed to affect the total polarizabilities, the variation of V_o in these Ca minerals is too small to observe the effect.     

Breakthroughs in the biodiversity, biogeography, biostratigraphy, and basin analysis of the Beaufort group

Over the past decade researchers working on the rocks of the Beaufort Group in the main Karoo Basin of South Africa have vastly increased our understanding of this important Permo-Triassic sequence. Many new fossil forms have been discovered, allowing for breakthroughs into the biodiversity, biogeography and biostratigraphy of the group. Taxonomic and phylogenetic advances are many and varied, and cover most of the vertebrate taxa, but with emphasis placed on the temnospondyl amphibians, archosauriforms and non-mammalian synapsids, in particular the anomodontia. Biostratigraphic breakthroughs have centered on the Middle Permian Eodicynodon and Tapinocephalus assemblage zones, the Late Permian Dicynodon Assemblage Zone, and the Triassic Lystrosaurus and Cynognathus assemblage zones. Correlation of these biozones with better dated sequences in Europe, Russia and China has allowed for many chronostratigraphic refinements, which are in turn vital for sequence stratigraphical analysis of the basin fill. Based on fossil data, both the lower (Ecca–Beaufort) and upper (Beaufort–Molteno) contacts of the group have been proved to be highly diachronous. The refined chronostratigraphic framework has also allowed for a better analysis of the basin evolution through time, particularly in terms of the correlation of external stimuli that affect basin sedimentation patterns.