辽西义县组火山岩40Ar/39Ar、K-Ar法年龄测定

义县组为辽西地区广泛分布的陆相火山-沉积地层,义县火山旋回分为 4个亚旋回.含珍稀化石的湖相沉积层与第二亚旋回火山岩伴生.运用激光微区 40Ar/39Ar法、常规 40Ar/39Ar阶段升温测年法和 K- Ar法,对义县旋回火山岩进行了系统的年龄测定,结果表明,直接覆盖义县组底砾岩的义县旋回第一亚旋回第一小旋回玄武岩的 K- Ar年龄为 (133.3± 2.6) Ma、 (133.6± 2.6) Ma,激光微区 40Ar/39Ar法给出的相关性很好的 Ar- Ar等时线年龄为 (132.9± 4.5) Ma,第三、第四小旋回玄武岩样品 40Ar/39Ar阶段升温获得平坦的年龄谱线,坪年龄分别为 (130.6± 0.5) Ma、 (127.7± 0.2) Ma;第二亚旋回玄武岩和流纹质凝灰岩样品 Ar- Ar等时线年龄为 (126.1± 1.7) Ma、 (127.4± 1.3) Ma,第三亚旋回火山岩全岩 K- Ar年龄为 (124.4± 2.4)～ (124.9± 2.4) Ma.义县火山旋回发生的时间大致介于 120～ 135 Ma之间, 义县组的时代应为早白垩世.     

内蒙古柳坝沟金矿床40Ar-39Ar年代学及铅同立素

内蒙古柳坝沟金矿床是华北地台北缘成矿带上,以广泛发育钾长石化为特色的大型金矿床.金矿体中钾长石的40 Ar-39Ar同位素和矿石的铅同位素特征表明:40Ar-39Ar年龄密度图中260～360 Ma峰值区反映了岩浆活动的主要时限,与区内岩体侵位年龄(220～350 Ma)相符.40Ar-39Ar坪年龄为(217.9±3...     

超高压变质岩多硅白云母的外来40Ar探讨

采用激光阶段加热 40Ar-39Ar定年技术, 测定了碧溪岭榴辉岩 6个多硅白云母的 Ar同位素组成.02BX030MS形成基本平坦的 40Ar-39Ar年龄谱, 数据点构成很好的正等时线, 加权平均年龄和等时线年龄均为 697 Ma, 这一年龄可能接近原岩年龄.DB-1MS、02BX018MS和 02BX019MS之 40Ar-39Ar年龄谱起伏较大, 表观年龄范围为～ 400 Ma至～ 680 Ma.在 40Ar/36Ar-39Ar/36Ar正等时线图解上, 这 3个样品数据点落在下拟合线 Reg-Ⅰ和上拟合线 Reg-Ⅲ之间.Reg-Ⅰ对应的年龄为 436～ 463 Ma, 与榴辉岩石榴子石原生流体包裹体年龄基本一致, 可能代表了榴辉岩超高压变质作用峰期的年龄;Reg-Ⅲ对应的年龄为 541～ 659 Ma, 最高年龄值小于 02BX030MS的年龄, 表明超高压变质作用使多硅白云母产生了不同程度的放射成因 40Ar部分丢失.继承 40Ar模型可以合理解释高压-超高压变质岩石之多硅白云母 40Ar-39Ar年龄明显偏老等地质现象.     

西天山北部晚古生代火山-浅侵位岩浆岩40Ar/39Ar同位素定年

西天山火山岩属玄武安山流纹岩建造,钙碱性(中钾、高钾)和橄榄玄粗岩系列。其^40Ar／^39Ar年龄范围为250～306Ma,以260～290Ma为高峰值。浅侵位岩浆岩属偏碱性、碱性岩石或高钾钙碱性系列岩石,^40Ar／^39Ar年龄范围为260～290Ma。综合Ar—Ar和Rb—Sr、U—Pb年龄资料,西天山地区火山—浅侵位岩浆活动高峰期发生在晚石炭世—早二叠世。^40Ar／^39Ar坪年龄资料还显示了晚二叠世、侏罗纪—早白垩世的热事件信息。对区内高钾钙碱性火山岩、橄榄玄粗岩和埃达克质岩石等富碱火成岩的年龄测定表明,本区构造格架的重大转折——由俯冲、碰撞造山的挤压,转向后碰撞的伸展、拉张——发生在石炭纪末—早二叠世(250～300Ma)期间。     

中国西部喀喇昆仑—昆仑山地区火山岩的~(40)Ar-~(39)Ar年龄及地质意义

本文对中国西部喀喇昆仑—昆仑山地区通天桥火山岩、阿鲁克库勒的9号和10号次火山岩获得的40Ar-39Ar年龄分别为69.2Ma、1.00Ma和0.37Ma,邦达错橄榄玄武岩的K-Ar年龄为44Ma,据此对青藏高原北部地区火山作用的时空演化规律进行探讨。     

藏北巴毛穷宗-羌巴欠火山岩K-Ar和40Ar-39Ar年代学研究

两种方法(K-Ar和^40Ar／^39Ar)测定藏北火山岩同位素地质年龄表明其相当于渐新世到中新世：巴毛穷宗钾质碱性火山岩为32Ma～19Ma，涌波错和羌巴欠为17Ma和14Ma～12Ma等，同位素地质年龄范围在32Ma～12Ma，而且火山喷溢作用，从南到北逐渐变新。其中在巴毛穷宗火山岩区获得32Ma的年龄，证实青藏高原的隆升至少在32Ma以前已经开始。     

银根-额济纳旗盆地苏红图坳陷早白垩世火山岩对阿尔金断裂研究的科学意义

通过对银根-额济纳旗盆地苏红图坳陷火山岩进行39Ar-40Ar同位素测年得到该套火山岩年龄值为(105.55±4.03)～(112.71土2.06)Ma,为早白垩世喷发物.对苏红图火山岩与位于阿尔金断裂周缘的酒西盆地红柳峡火山岩的年龄及地化特征进行了对比研究,认为红柳峡火山岩及苏红图火山岩均为阿尔金-恩格尔乌苏断裂断裂...     

华北地块南缘中段中生代花岗质岩石的40Ar-39Ar年代学研究

对华北地块南缘4个中生代花岗质岩体中的角闪石和黑云母进行了40Ar-39Ar定年研究。结果表明,陕西黑山村岩体黑云母花岗闪长岩中黑云母的40Ar-39Ar坪年龄为126. 6±0. 3Ma,河南马家湾岩体细粒黑云母花岗闪长岩中黑云母的40Ar-39Ar坪年龄为126. 6±0. 2Ma,河南洛宁南八百坡岩体黑云母二长花岗岩中角闪石的40Ar-39Ar坪年龄为128. 3±0. 3Ma,山西蚕坊岩体花岗闪长岩中角闪石的40Ar-39Ar坪年龄为129. 2±0. 2Ma。上述结果显示华北地块南缘中生代的岩浆活动主要发生在早白垩世。该期岩浆的产生应与中国东部早白垩世的伸展环境相联系。     

宁芜盆地凹山和东山铁矿床中阳起石的激光39Ar-40Ar年代学研究

文章通过对凹山和东山铁矿床中特征的组合矿物之一伟晶状阳起石进行激光39Ar-40Ar法定年,精确测定了玢岩铁矿的成矿时代。其中东山铁矿中新鲜阳起石(黑绿色)的39Ar-40Ar等时线年龄在126～129Ma之间,与赋矿围岩大王山组火山岩中角闪石的等时线年龄(127Ma)一致,证明成矿与成岩密切相关,成矿与成岩是同时期的产物。而凹山铁矿中蚀变阳起石(灰绿色)的39Ar-40Ar等时线年龄为(114±16)Ma。2种阳起石分别形成于成矿作用的不同阶段,黑绿色新鲜阳起石与磷灰石、磁铁矿同期形成,形成于岩浆向热液演化的高温阶段,在成岩和成矿之后的冷却过程中,矿体和潜火山岩体具有相同的闪石封闭温度(500℃±);而灰绿色蚀变阳起石形成于中期阳起石(透辉石)-钠长石-磷灰石-磁铁矿化矿体围岩蚀变阶段。     

大别山碧溪岭榴辉岩450 Ma年龄信息:石榴子石流体包裹体40Ar-39Ar定年初步结果

高压-超高压变质岩常含有过剩40Ar,排除过剩40Ar的干扰是获得可靠40Ar-39Ar年龄的关键.本文试图从流体包裹体40Ar-39Ar定年的角度,探讨榴辉岩40Ar-39Ar定年技术与过剩40Ar问题.采用真空击碎法提取流体包裹体,对碧溪岭浅色榴辉岩石榴子石进行40Ar-39Ar定年,获得了下降型年龄谱:最初9个阶段年龄谱总体上呈逐渐下降,表观年龄从2 226 Ma下降到753 Ma,这是次生包裹体(含过剩40Ar)与原生包裹体(不含过剩40Ar)混合的结果;第10阶段至第22阶段(末阶段),年龄谱呈平缓波动,表观年龄变化小,对应坪年龄为(449±18)Ma(2σ,39Ar占59.5%),这是微小的原生流体包裹体的贡献,此13个数据点在36Ar/40Ar-39Ar/40Ar图上构成线性关系很好的反等时线,对应的等时线年龄(448±34)Ma代表了石榴子石的结晶年龄,40Ar/36Ar初始比值(292±5)表明原生包裹体不含过剩40Ar.     

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.     

Columbus,the discovery of America,and Russia

The discovery of a new continent that was later called America by Christopher Columbus some five hundred years ago, has in one way or another, influenced people the World over. The extraordinary significance of this event for mankind is displayed by the dimension of the consequences and the variety of reactions among nations and communities of the “Old World”.     

Roles of xenomelts,xenoliths, xenocrysts,xenovolatiles, residues,and skarns in the genesis,transport, and localization of magmatic Fe-Ni-Cu-PGE sulfides and chromite

Most sulfide-rich magmatic Ni-Cu-(PGE) deposits form in dynamic magmatic systems by partial melting S-bearing wall rocks with variable degrees of assimilation of miscible silicate and volatile components, and generation of barren to weakly-mineralized immiscible Fe sulfide xenomelts into which Ni-Cu-Co-PGE partition from the magma. Some exceptionally-thick magmatic Cr deposits may form by partial melting oxide-bearing wall rocks with variable degrees of assimilation of the miscible silicate and volatile components, and generation of barren Fe ± Ti oxide xenocrysts into which Cr-Mg-V ± Ti partition from the magma. The products of these processes are variably preserved as skarns, residues, xenoliths, xenocrysts, xenomelts, and xenovolatiles, which play important to critical roles in ore genesis, transport, localization, and/or modification. Incorporation of barren xenoliths/autoliths may induce small amounts of sulfide/chromite to segregate, but incorporation of sulfide xenomelts or oxide xenocrysts with dynamic upgrading of metal tenors (PGE > Cu > Ni > Co and Cr > V > Ti, respectively) is required to make significant ore deposits. Silicate xenomelts are only rarely preserved, but will be variably depleted in chalcophile and ferrous metals. Less dense felsic xenoliths may aid upward sulfide transport by increasing the effective viscosity and decreasing the bulk density of the magma. Denser mafic or metamorphosed xenoliths may also increase the effective viscosity of the magma, but may aid downward sulfide transport by increasing the bulk density of the magma. Sulfide wets olivine, so olivine xenocrysts may act as filter beds to collect advected finely dispersed sulfide droplets, but other silicates and xenoliths may not be wetted by sulfides. Xenovolatiles may retard settling of – or in some cases float – dense sulfide droplets. Reactions of sulfide melts with felsic country rocks may generate Fe-rich skarns that may allow sulfide melts to fractionate to more extreme Cu-Ni-rich compositions. Xenoliths, xenocrysts, xenomelts, and xenovolatiles are more likely to be preserved in cooler basaltic magmas than in hotter komatiitic magmas, and are more likely to be preserved in less dynamic (less turbulent) systems/domain/phases than in more dynamic (more turbulent) systems/domains/phases. Massive to semi-massive Ni-Cu-PGE and Cr mineralization and xenoliths are often localized within footwall embayments, dilations/jogs in dikes, throats of magma conduits, and the horizontal segments of dike-chonolith and dike-sill complexes, which represent fluid dynamic traps for both ascending and descending sulfides/oxides. If skarns, residues, xenoliths, xenocrysts, xenomelts, and/or xenovolatiles are present, they provide important constraints on ore genesis and they are valuable exploration indicators, but they must be included in elemental and isotopic mass balance calculations.     

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.     

山西五台山区滹沱群变质玄武岩岩石学、地球化学特征及其成因意义

在野外地质调查的基础上,选取滹沱群豆村亚群底部四集庄组玄武岩、顶部青石村组玄武岩和东冶亚群中下部河边村组玄武岩,进行岩石学和地球化学研究。分析结果表明：玄武岩主量元素高TiO2、TFeO,低MgO,具有演化的基性岩浆的特征。稀土元素含量相对较高,具有弱—中等程度的轻稀土元素富集,中等程度的轻重稀土元素分异,轻微的Eu异常;玄武岩中Cr、Ni含量变化较大,但与Mg#具有很好的正相关性。微量元素配分图解中具有明显的Sr负异常,部分样品具有Nb、Ta和Ti负异常,无Zr、Hf负异常,与岛弧火山岩不同;同时Nb、Ta无分异,Zr/Hf值较高,具有板内玄武岩浆的特征。综合分析认为,滹沱群玄武岩可能形成于板内裂谷环境。在岩浆上升过程中发生橄榄石与尖晶石的分离结晶作用,同时不同程度地受到地壳的混染。     

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.     

Climate,disasters, wars and the collapse of the Ming Dynasty

Based on the historical records of natural disasters and human wars of the final 35 years in the late Ming Dynasty (1610–1644 AD) obtained using different spatial scales, a set of grading systems were established to classify, grade and present these records and their spatiotemporal characteristics. From natural and human perspectives to quantitative analyses of the direct causes of the collapse of the Ming Dynasty, the author draws conclusion regarding a total of six immediate factors, which were, according to the rate of contribution from high to low, internal rebellions, drought, inter-ethnic conflicts, locust, flood and external wars. Among these causes, human factors accounted for approximately 47%, while natural factors accounted for approximately 53%. Attribution analysis indicated that the basin areas in east China were sensitive to climate change during the Ming Dynasty. Severe drought and locusts in a cooling environment were the main natural causes, while frequent internal rebellions and inter-ethnic conflicts influenced by financial crisis were the major human factors. Although natural factors accounted for a greater percentage than human factors in the rate of contribution to the collapse of the Ming Dynasty, they were the only external factors impacting social development and changes.