首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 312 毫秒
1.
塔里木板块北缘额济纳旗老硐沟金矿床发育系列蚀变中基性岩脉,其形成时代与成因对制约金成矿作用及区域古亚洲洋的演化提供了研究窗口。本文在老硐沟金矿区Ⅱ矿段采集系列辉绿岩脉及与金成矿相关的蚀变闪长玢岩脉样品,进行了锆石LA-ICP-MS U-Pb定年、Hf同位素组成和全岩元素分析。结果表明,辉绿岩脉和闪长玢岩脉侵位时代分别为(286.5±1.7) Ma和(243.2±1.1) Ma,即早二叠世和中三叠世,二者年龄先后顺序与野外观察的交切关系相符。根据金矿体穿插闪长玢岩脉的特征,限定金成矿时代略晚于243 Ma。辉绿岩脉锆石εHf(t)为-3.67～0.97,全岩元素组成表现为准铝质钙碱性系列,反映岩浆源区既有新元古代新生地壳组分,又有中元古代古老地壳组分。蚀变闪长玢岩脉εHf(t)=-0.07～-4.76,全岩元素组成是过铝质钾玄岩系列(富钾特征受到矿区钾化蚀变的影响),指示其岩浆主要源于中元古代的地壳物质熔融。综合塔里木地块北缘晚古生代至早中生代构造演化史,提出晚石炭世—早二叠世北山地区古洋盆消减,洋壳俯冲导致地幔楔部分熔融,岩浆上侵至浅部断裂冷...  相似文献   

2.
本文对冈底斯谢通门地区的三个花岗岩体进行了LA-ICP-MS锆石U-Pb定年、Hf同位素分析以及岩体侵位深度研究。研究结果表明,三个岩体的锆石U-Pb同位素年龄分别为43.5±0.6 Ma、44.9±0.5 Ma和48.3±1.4 Ma。锆石的Hf同位素研究显示,样品xy911的εHf(t)值介于–5.1~0.35,为典型的壳幔混合型,Hf同位素的二阶段模式年龄平均值为1142 Ma,表明其主要岩浆源区以古老地壳基底的部分熔融为主,在此过程中可能伴有幔源岩浆或新生下地壳的贡献。而样品xy957和样品xy961具有相似的Hf同位素特征,εHf(t)均为正值;样品xy957的εHf(t)值介于0.23~7.31,平均值为5.07,样品xy961的εHf(t)值介于2.12~5.82,平均值为4.70,其二阶段模式年龄平均值分别为764 Ma、792 Ma,表明它们的源岩以新生地壳的部分熔融为主或有大量幔源物质的加入,同时,也混有少量古老陆壳的成分。根据角闪石压力计计算得出,样品xy911、xy957、xy961侵位深度分别为9.36 km、9.53 km和10.89 km,为中深成侵入相。综合分析表明,谢通门复式岩体主要以新生地壳物质的部分熔融为主,在岩浆演化或上升过程中混染了部分拉萨地体的古老物质;此外该复式岩体的形成可能和新特提斯洋板片的断离引起地幔物质上涌有关。  相似文献   

3.
安徽宣城茶亭Cu-Au矿床是长江中下游成矿带内新发现的一个斑岩型矿床。文章对该矿床赋矿石英闪长玢岩进行了锆石LA-ICP-MS U-Pb同位素年龄及岩石主量与微量元素、Sr-Nd同位素和锆石Lu-Hf同位素分析,旨在探讨其岩浆起源和岩石成因。锆石U-Pb同位素年龄测定结果显示,赋矿石英闪长玢岩形成年龄为137.8±1.3 Ma(MSWD=0.72),为早白垩世岩浆活动的产物。岩石主量元素显示其具富碱富钠特征,为亚碱性准铝质高钾钙碱性系列岩石。岩石微量元素显示其富集大离子亲石元素K、Rb、Sr、Ba和轻稀土元素,弱富集Zr和Hf,亏损高场强元素Nb、Ta、Ti等,稀土元素配分型式表现为无明显Eu异常。岩石(~(87)Sr/~(86)Sr)_i值介于0.706403~0.707903之间,ε_(Nd)(t)值介于-7.4~-13.3之间(t=137.8 Ma)。锆石ε_(Hf)(t)值为-4.25~-11.75(t=137.8 Ma)。主量元素、微量元素、Sr-Nd同位素和锆石Hf同位素地球化学特征均指示,赋矿石英闪长玢岩可能是富集岩石圈地幔与扬子下地壳物质部分熔融形成的岩浆混合后侵位的产物。对比长江中下游成矿带断隆区和断凹区侵入岩发现,宣城茶亭矿床赋矿石英闪长玢岩与长江中下游成矿带断凹区(宁芜、庐枞矿集区等)侵入岩,无论是岩石主量与微量元素地球化学特征还是同位素地球化学特征都存在一定差异,而与断隆区(铜陵矿集区)赋矿岩浆岩表现出一致性,暗示宣城茶亭矿床赋矿石英闪长玢岩与长江中下游成矿带断隆区岩浆岩有着基本一致的成岩物质来源和岩石成因机制,是富集岩石圈地幔熔融岩浆及其引起的下地壳物质部分熔融岩浆发生岩浆混合作用并伴随着一定程度的分离结晶作用进而浅成侵位形成。  相似文献   

4.
258高地金矿床地处黑龙江省完达山成矿带东部,矿化与岩浆侵入活动密切相关。文章利用锆石LA-ICP-MS U-Pb定年方法,对258高地金矿区的二长花岗岩、花岗闪长岩及闪长玢岩进行了年代学研究,获得258金矿区花岗闪长岩的成岩年龄为(118.3±1.1)Ma;3件二长花岗岩样品的成岩年龄分别为(130.5±0.8)Ma、(122.1±0.7)Ma、(118.0±0.9)Ma;2件闪长玢岩的成岩年龄分别为(119.5±1.3)Ma、(107.4±2.2)Ma,表明本区中酸性岩体侵位时代介于131~107 Ma,与西太平洋构造域的早白垩世演化有关。定年结果同时表明矿区存在3期岩浆活动,其中122~118 Ma的二长花岗岩与花岗闪长岩、闪长玢岩的年龄在误差范围内一致,且与金矿成矿关系密切。岩石地球化学显示区内的中酸性侵入岩均为高钾钙碱性过铝质岩石,花岗闪长岩和二长花岗岩具有重熔型岩浆岩的特征,可能是加厚地壳物质部分熔融的产物;闪长玢岩脉具有典型壳幔源岛弧岩浆岩的特点。综合研究认为258高地金矿床形成于与板块俯冲有关的活动大陆边缘环境。  相似文献   

5.
雄村铜金矿Ⅱ号矿体在2007-2008年取得了重大的找矿突破,详细的地质编录成果表明,矿体同样受含眼球状石英斑晶的角闪石英闪长玢岩和角闪石英闪长玢岩控制.含眼球状石英斑晶的角闪石英闪长玢岩和角闪石英闪长玢岩的锆石U-Pb年龄已经确定(164～177 Ma),因此,雄村铜金矿不同地质体的云母类、长石类矿物Ar-Ar同位素年龄的测定显得尤为关键.文章通过对穿切I号矿体的黑云母花岗闪长岩、云煌岩脉的黑云母Ar-Ar同位素测年,结合其他研究者的成果,得到一组十分重要的年龄数据.穿插矿体的黑云母花岗闪长岩中的黑云母(样号6187-335)坪年龄(46.96±0.42)Ma,穿插矿体的无矿化的云煌岩(5053-324.4)(Cu含量0.0551%,Au含量0.034 g/t,Ag0.6 g/t)中的黑云母给出了一个较好的似坪年龄,加权平均年龄为(49.59±0.58)Ma.结合其他研究者测定的中侏罗世侵位的角闪石英闪长玢岩(不含矿)[锆石U-Pb年龄为(177.1±2.0)Ma]中黑云母的At-At同位素年龄为(48.57±0.31)Ma;含矿凝灰岩围岩[锆石U-Pb年龄为(176±5)Ma,MS3VD=0.63}的蚀变绢云母Ar-Ar年龄为(47.07±0.30)Ma;似伟晶岩中长石的At-At年龄为(47.62±0.7)Ma,认为不同形成时代、不同产出空间、不同矿化程度的地质体的云母类、长石类矿物的Ar-Ar同位素年龄的一致性,反映了后期岩浆热事件对中侏罗世早期形成的地质体和矿体的黑云母氩同位素体系产生了较强的扰动或置换.谢通门大岩基黑云母花岗闪长岩的侵位致使各地质体发生显著的退变质,形成典型的角岩化带,这种退变质的时限在46-48 Ma之间的始新世lutetian期,进而认为各地质体中云母类矿物的~(40)Ar/~(39)Ar同位素年龄不能作为成矿年龄.  相似文献   

6.
宁芜火山岩盆地是长江中下游成矿带中最重要的矿集区之一,以产出玢岩型铁矿而著称。盆地内的岩浆活动产物可分为龙王山组,大王山组,姑山组和娘娘山组4个旋回火山岩及相关浅成侵入岩。本文对该盆地中凹山铁矿的成矿母岩——辉长闪长玢岩进行了精确的锆石U-Pb定年和Hf同位素组成测定。3个样品的锆石U-Pb年龄分别为(123±1)Ma,(127±3)Ma和(125±2)Ma。前人已对该盆地中火山岩开展过较多的定年工作,获得大王山组的锆石U-Pb年龄为127~131Ma。因此,与成矿密切相关的辉长闪长玢岩与第二旋回大王山组火山岩同期,形成年龄相近或略晚于火山岩。辉长闪长玢岩中锆石εHf(t)值为-6.3~-8.6,结合前人的地球化学数据,该岩石的形成可能与软流圈地幔上涌、富集岩石圈地幔熔融并与地壳物质混合有关,这一过程发生于华南约125Ma时岩石圈强烈伸展时期。同位素组成特征表明,与盆地内火山岩相比,宁芜浅成侵入岩形成过程中有更多的地壳物质加入。  相似文献   

7.
梅山铁多金属矿床是宁芜盆地内代表性矿床之一,其Fe-Cu-Au-Mo矿化与辉长闪长玢岩密切相关。本文对含矿辉长闪长玢岩及矿体下部的新鲜辉长闪长玢岩进行LA-MC-ICP-MS锆石U-Pb定年,获得年龄分别为(137.8±1.7)Ma、(141.2±1.0)Ma。因此辉长闪长玢岩形成时间应在138~141 Ma,伴随的Fe-Cu-Au-Mo矿化稍晚,都属于早白垩世,受区域岩石圈伸展和减薄作用制约。根据年代学和地质事实证据,初步认为宁芜盆地早白垩世火山活动从北段开始,火山活动持续时间至少为7~10 Ma。辉长闪长玢岩中古老锆石年龄变化于1898~1903 Ma、1163 Ma和292~296 Ma,时代分别为古元古代、新元古代和早二叠纪,暗示着岩浆上侵过程中基底岩石对岩浆可能有混染作用,表明长江中下游成矿带存在早元古代结晶基底和中—晚元古代褶皱基底的"双层结构"。  相似文献   

8.
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。  相似文献   

9.
通过对延边小西南岔大型富金铜床矿区产出的与成矿密切的角闪花岗闪长岩、黑云花岗闪长岩、黑云二长花岗岩(花岗杂岩)侵入体和闪长玢岩岩脉的地质、岩相学和元素地球化学研究,结合单颗粒锆石CL图象特征及精细测年结果,初步确定:它们的岩浆就位发生在晚中生代早白垩世末期(112 Ma～102 Ma),适值伊泽奈崎板块向古亚洲板块俯冲的大陆边缘环境;金铜矿化发生在角闪花岗闪长岩(111.7 Ma±2.8 Ma)、黑云花岗闪长岩(106.7 Ma±1.6 Ma)、黑云二长花岗岩(104.6 Ma±2.5 Ma)与闪长玢岩(102.1Ma±2.2 Ma)的就位之间;花岗杂岩是先存的岩石圈地幔受到俯冲大洋板片提供流体的交代,形成的次生岩石圈地幔,次生岩石圈地幔的部分熔融产生的埃达克质岩浆在MOSH面附近与下地壳重熔产生的钾质熔体混合,混合后的岩浆经以斜长石为主的矿物相分离结晶作用先后上侵就住形成;而闪长玢岩岩脉则是埃达克质岩浆直接上侵就位形成;矿质主要来自俯冲大洋板块,埃达克岩浆和地壳重熔岩浆的形成以及两者的混合作用、混合岩浆的结晶分离作用是导致成矿物质活化、迁移、富集的根源.  相似文献   

10.
宋明春  赵庆龄 《地质通报》2004,23(12):1254-1258
对苏鲁超高压变质带日照官山地区侵入于榴辉岩中的原生块状闪长玢岩进行了锆石SHRIMP年龄分析。结果显示,数据点构成的不一致线与一致线上交点年龄为(876±62)Ma,下交点年龄为(201±20)Ma。上交点年龄为残余锆石年龄,下交点年龄大致代表了闪长玢岩的形成时代。苏鲁超高压变质带中存在较广泛的印支期岩浆热事件。假定超高压变质作用发生于228Ma,推算出闪长玢岩侵位前超高压变质岩的折返速率大致为3.63mm/a,闪长玢岩侵位后超高压变质岩的折返(剥蚀)速率大致为0.03mm/a。  相似文献   

11.
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.  相似文献   

12.
Between 1985 and 1991, two new mountain protected areas (MTNPA) covering more than 35,000 km2 and based on participatory management models — the Makalu-Barun National Park and Conservation Area, Nepal, and Qomolangma Nature Preserve, Tibet Autonomous Region — were successfully established through the collaborative efforts of Woodlands Mountain Institute and conservationists in China and Nepal. Characteristics common to both projects include the importance of establishing (1) effective rationales, (2) local support constituencies, (3) a senior advisory group, (4) a task force, (5) linkages between conservation and development, and (6) fund raising mechanisms. The lessons derived from the experiences of Woodlands Mountain Institute are of significant value to others in preserving MTNPA. Increased collaboration and communication between all interested in conservation, however, will remain a critical component for expanding mountain protected area coverage to throughout the world.  相似文献   

13.
This article advances critical geographies of youth through examining the spatiality implicit in the imagined futures of young women in rural India. Geographers and other scholars of youth have begun to pay more attention to the interplay between young people’s past, present, and imagined futures. Within this emerging body of scholarship the role of the family and peer group in influencing young people’s orientations toward the future remain underexamined. Drawing on eleven months of ethnographic fieldwork, my research focuses on a first generation of college-going young women from socioeconomically marginalized backgrounds in India’s westernmost state of Gujarat. I draw on the “possible selves” theoretical construct in order to deploy a flexible conceptual framework that links imagined post-educational trajectories with motivation to act in the present. In tracing the physical movement of these young women as they navigate and complete college, my analysis highlights the ways in which particular kinds of spaces and spatial arrangements facilitate and limit intra- and inter-generational contact, and the extent to which this affects young women’s conceptions of the future. I conclude by considering the wider implications of my research for ongoing debates surrounding youth transitions, relational geographies of age, and education in the Global South.  相似文献   

14.
Emilio Biagini 《GeoJournal》1998,44(2):163-165
  相似文献   

15.
《Chemical Geology》2007,236(1-2):13-26
We examined the coprecipitation behavior of Ti, Mo, Sn and Sb in Ca–Al–Mg fluorides under two different fluoride forming conditions: at < 70 °C in an ultrasonic bath (denoted as the ultrasonic method) and at 245 °C using a Teflon bomb (denoted as the bomb method). In the ultrasonic method, small amounts of Ti, Mo and Sn coprecipitation were observed with 100% Ca and 100% Mg fluorides. No coprecipitation of Ti, Mo, Sn and Sb in Ca–Al–Mg fluorides occurred when the sample was decomposed by the bomb method except for 100% Ca fluoride. Based on our coprecipitation observations, we have developed a simultaneous determination method for B, Ti, Zr, Nb, Mo, Sn, Sb, Hf and Ta by Q-pole type ICP-MS (ICP-QMS) and sector field type ICP-MS (ICP-SFMS). 9–50 mg of samples with Zr–Mo–Sn–Sb–Hf spikes were decomposed by HF using the bomb method and the ultrasonic method with B spike. The sample was then evaporated and re-dissolved into 0.5 mol l− 1 HF, followed by the removal of fluorides by centrifuging. B, Zr, Mo, Sn, Sb and Hf were measured by ID method. Nb and Ta were measured by the ID-internal standardization method, based on Nb/Mo and Ta/Mo ratios using ICP-QMS, for which pseudo-FI was developed and applied. When 100% recovery yields of Zr and Hf are expected, Nb/Zr and Ta/Hf ratios may also be used. Ti was determined by the ID-internal standardization method, based on the Ti/Nb ratio from ICP-SFMS. Only 0.053 ml sample solution was required for measurement of all 9 elements. Dilution factors of ≤ 340 were aspirated without matrix effects. To demonstrate the applicability of our method, 4 carbonaceous chondrites (Ivuna, Orgueil, Cold Bokkeveld and Allende) as well as GSJ and USGS silicate reference materials of basalts, andesites and peridotites were analyzed. Our analytical results are consistent with previous studies, and the mean reproducibility of each element is 1.0–4.6% for basalts and andesites, and 6.7–11% for peridotites except for TiO2.  相似文献   

16.
The contents of As, Cd, Cu, Cr, Mg, Mn, Ni, Pb and Zn have been determined in sediment and water samples from Valle de las Garzas estuary and Port Manzanillo (Colima, Mexico) using ICP-AES. The concentrations of these elements were used for a comparative study to determine the distribution of heavy metals and to evaluate which elements reflect natural or anthropogenic backgrounds. For this purpose, seven sampling points were selected: Four of them correspond to the lagoon, and three were situated in the port. Statistical analysis of the mineral content was assessed. Initially, data comparison was assessed by statistical tests for each variable. Principal component analysis was then applied considering the influence of all variables at the same time by obtaining the distribution of samples according to their scores in the principal component space. In this way, four studies were carried out: (1) study of sediments collected during the dry season; (2) study of sediments collected during the rainy season; (3) comparative study between sediments from rainy and dry season; and (4) study of water composition collected during rainy season. From the results of the performed analyses, it can be concluded that metals distribution pattern reflected natural and anthropogenic backgrounds (e.g., sediments from the lagoon, situated at the beginning of the rain channel, presented high contents of Zn and Cu, perhaps related to anthropogenic activities or the influence of igneous sediments).  相似文献   

17.
Models have become so fashionable that many scientists and engineers cannot imagine working without them. The predominant use of computer codes to execute model calculations has blurred the distinction between code and model. The recent controversy regarding model validation has brought into question what we mean by a ‘model’ and by ‘validation.’ It has become apparent that the usual meaning of validation may be common in engineering practice and seems useful in legal practice but it is contrary to scientific practice and brings into question our understanding of science and how it can best be applied to such problems as hazardous waste characterization, remediation, and aqueous geochemistry in general. This review summarizes arguments against using the phrase model validation and examines efforts to validate models for high-level radioactive waste management and for permitting and monitoring open-pit mines. Part of the controversy comes from a misunderstanding of ‘prediction’ and the need to distinguish logical from temporal prediction. Another problem stems from the difference in the engineering approach contrasted with the scientific approach. The reductionist influence on the way we approach environmental investigations also limits our ability to model the interconnected nature of reality. Guidelines are proposed to improve our perceptions and proper utilization of models. Use of the word ‘validation’ is strongly discouraged when discussing model reliability.  相似文献   

18.
The shape of sedimentary particles may carry important information on their history. Current approaches to shape classification (e.g. the Zingg or the Sneed and Folk system) rely on shape indices derived from the measurement of the three principal axes of the approximating tri-axial ellipsoid. While these systems have undoubtedly proved to be useful tools, their application inevitably requires tedious and ambiguous measurements, also classification involves the introduction of arbitrarily chosen constants. Here we propose an alternative classification system based on the (integer) number of static equilibria. The latter are points of the surface where the pebble is at rest on a horizontal, frictionless support. As opposed to the Zingg system, our method relies on counting rather than measuring. We show that equilibria typically exist on two well-separated (micro and macro) scales. Equilibria can be readily counted by simple hand experiments, i.e. the new classification scheme is practically applicable. Based on statistical results from two different locations we demonstrate that pebbles are well mixed with respect to the new classes, i.e. the new classification is reliable and stable in that sense. We also show that the Zingg statistics can be extracted from the new statistics; however, substantial additional information is also available. From the practical point of view, E-classification is substantially faster than the Zingg method.  相似文献   

19.
Partition coefficients of Hf,Zr, and REE between zircon,apatite, and liquid   总被引：25，自引：2，他引：25  
Concentration ratios of Hf, Zr, and REE between zircon, apatite, and liquid were determined for three igneous compositions: two andesites and a diorite. The concentration ratios of these elements between zircon and corresponding liquid can approximate the partition coefficient. Although the concentration ratios between apatite and andesite groundmass can be considered as partition coefficients, those for the apatite in the diorite may deviate from the partition coefficients. The HREE partition coefficients between zircon and liquid are very large (100 for Er to 500 for Lu), and the Hf partition coefficient is even larger. The REE partition coefficients between apatite and liquid are convex upward, and large (D=10–100), whereas the Hf and Zr partition coefficients are less than 1. The large differences between partition coefficients of Lu and Hf for zircon-liquid and for apatite-liquid are confirmed. These partition coefficients are useful for petrogenetic models involving zircon and apatite.  相似文献   

20.
Materials and energy are the interdependent feedstocks of economic systems, and thermodynamics is their moderator. It costs energy to transform the dispersed minerals of Earth's crust into ordered materials and structures. And it costs materials to collect and focus the energy to perform work — be it from solar, fossil fuel, nuclear, or other sources. The greater the dispersal of minerals sought, the more energy is required to collect them into ordered states.But available energy can be used once only. And the ordered materials of industrial economies become disordered with time. They may be partially reordered and recycled, but only at further costs in energy. Available energy everywhere degrades to bound states and order to disorder — for though entropy may be juggled it always increases. Yet industry is utterly dependent on low entropy states of matter and energy, while decreasing grades of ore require ever higher inputs of energy to convert them to metals, with ever increasing growth both of entropy and environmental hazard.Except as we may prize a thing for its intrinsic qualities — beauty, leisure, love, or gold — low-entropy is the only thing of real value. It is worth whatever the market will bear, and it becomes more valuable as entropy increases. It would be foolish of suppliers to sell it more cheaply or in larger amounts than their own enjoyment of life requires, whatever form it may take. For this reason, and because of physical constraints on the availability of all low-entropy states, the recent energy crises is only the first of a sequence of crises to be expected in energy and materials as long as current trends continue.The apportioning of low-entropy states in a modern industrial society is achieved more or less according to the theory of competitive markets. But the rational powers of this theory suffer as the world grows increasingly polarized into rich, over-industrialized nations with diminishing resource bases and poor, supplier nations with little industry. The theory also discounts posterity, the more so as population density and percapita rates of consumption continue to grow. A new social, economic, and ecologic norm that leads to population control, conservation, and an apportionment of low-entropy states across the generations is needed to assure to posterity the options that properly belong to it as an important but voiceless constituency of the collectivity we call mankind.
Zusammenfassung Rohstoffe und Energie sind die Grundlagen unseres ökonomischen Systems, das von den Gesetzen der Thermodynamik bestimmt wird. Es kostet Energie, um die auf der Erde verteilten Rohstoffe diesem System zuzuführen. Andererseits braucht man Rohstoffe, um die Energie nutzbar zu machen.Die verfügbare Energie kann nur einmal genutzt werden und das Material verbraucht sich. Verbrauchtes Material kann teilweise zur weiteren Nutzung zurückgeführt werden, das kostet wiederum Energie. Die verfügbare Energie nimmt überall ab, und einmal geschaffene Ordnung gerät wieder in Unordnung — das heißt, die Entropie des Systems nimmt ständig zu. Die Industrie ist jedoch abhängig von einem niedrigen Entropiezustand sowohl der Materie als auch der Energie.Je ärmer die Erze sind, um so höher wird die Energie sein, um sie in Metalle umzuwandeln, wobei die Entropie und die Belastung der Umwelt ständig zunimmt.Außer den Dingen, die wir wegen höherer ideeller Werte schätzen, ist eine niedrige Entropie der einzige realistische Wertmaßstab, und der wirkliche Wertzuwachs ist nur an einer höheren Entropie zu messen. Es ist unverantwortlich, Dinge, die eine höhere Entropie bedingen, billiger zu verkaufen oder in größerer Menge zu erzeugen, als unbedingt notwendig ist. Da wir dies heute in unserem Handeln nicht berücksichtigen, ist die derzeitige Energiekrise nur der Anfang einer Folge von Krisen, die Energie und Rohstoffe betreffen, solange wir nicht umdenken.Die Verteilung von niedriger Entropie in einer modernen Industriegesellschaft wird mehr oder weniger nach dem Prinzip der konkurrierenden Märkte erreicht. Das selbstregulierende System gerät jedoch mit zunehmender Polarisierung in reiche Industrienationen mit abnehmenden Ressourcen und armen Nationen mit geringer Industrialisierung in Unordnung. Dieses Prinzip berücksichtigt auch nicht die Nachwelt, vor allem wenn die Bevölkerungsdichte stetig zunimmt und die Konsumbedürfnisse anwachsen. Es sind neue soziale, ökonomische und ökologische Normen notwendig, die zur Populationskontrolle, zur Erhaltung der Umwelt und zu einem Zustand niedriger Entropie für zukünftige Generationen führen. Die nach uns kommenden Menschen haben ein Anrecht darauf.
Résumé Matériaux et énergie sont les sources des systèmes économiques et sont régis par les lois de la thermodynamique. Il faut de l'énergie pour transformer les ressources minérales dispersées dans la croûte terrestre en matériaux et structures ordonnancées. Et il faut des matériaux pour receuillir et concentrer l'énergie, qu'elle soit solaire ou atomique, ou provienne de combustibles fossiles ou d'autres sources. Plus les minéraux recherchés sont dispersés et plus est côuteuse l'énergie pour leur donner une ordonnance.Or l'énergie disponsible ne peut être utilisée qu'une seule fois. Et les matériaux ordonnancés des économies industrielles se dégradent avec le temps. Ils peuvent être remis partiellement en état et recyclés, mais pour cela il faut de nouveau de l'énergie. Partout l'énergie disponible se dégrade et l'ordre devient désordre; -malgré toutes les jongleries possibles l'entropie augmente toujours.L'industrie dépend clairement d'états de basse entropie tant en ce qui concerne les matériaux que l'énergie, tandis que plus pauvres sont les minerais, plus; élevée est l'énergie à mettre en jeu pour en extraire les métaux, avec toujours augmentation à la fois de l'entropie et de la degradation des milieux.A l'exception de ce que nous apprécions pour leur valeur intrinsèque — la beauté, le loisir, l'amour ou l'or — la basse entropie est la seule chose de réelle valeur. Son prix est réglé par le marché, et sa valeur augmente au fur et à mesure que l'entropie s'accroît. Ceux qui en disposent seraient insensés de la vendre à bas prix ou en quantité supérieure à ce qu'exige leur propre niveau de vie. Pour cette raison, et à cause des contraintes physiques liées à la disponibilité en états de basse entropie, la récente crise d'énergie n'est, en ce qui concerne les matières premières et l'énergie, que la première d'une série de crises auxquelles il faut s'attendre aussi longtemps que se poursoit la marche actuelle des étènements.Dans les sociétés industrielles modernes, les approvisionnement en basse entropie s'effectuent plus ou moins conformément à la théorie de la concurrence des marchés. Cependant la rationalité de cette théorie se ressent de l'accentuation croissante de la polarisation, à l'échelle du monde, en nations riches, surindustrialisées, à ressources de base décroissantes, et en nations pauvres, sous-industrialisées, mais fournisseurs de resources-naturelles. De plus cette théorie ne tient pas compte de notre postérité, et ce, en face d'une densité de population et d'un taux de la consommation par tête d'habitant en augmentation continue.Nous avons donc besoin de nouvelles normes sociales, économiques et écologiques qui conduisent au contrôle de la population, à la conservation et à la répartition des états de basse entropie à travers les générations pour assurer à notre postérité les options qui leur riviennent de droit comme une constituante importante, mais encore muette, de la collectivité que nous appelons l'Humanité.
, . . . . , . , .. . , , . , , , . , - , , , : , , . .. , , , , , . . , : , — , . , . , , , . .

Dedicated with appreciation to Nicholas Georgescu-Roegen, distinguished economist, realist among cornucopians  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号