冰碛垄表面碎屑物质宇生核素暴露测年可行性研究

原地生宇宙成因核素(宇生核素)~(10)Be和~(26)Al暴露测年技术已广泛应用于各种地貌年代测定,尤其是在冰川地貌年代测定中备受青睐。多数学者通常选择冰碛垄表面散布的冰川漂砾作为测年对象。然而,冰川漂砾在暴露测年研究中存在暴露后期翻转、不等时暴露等问题,不仅影响冰川地貌测年的精度,而且难以获得较老的冰川地貌年代。冰碛垄表面碎屑物质,一直附着于冰碛垄"表面",可以规避冰川漂砾测年存在的不等时暴露问题,而且可以减少测试样本量、降低测试费用。因此,本文尝试探讨利用冰碛垄表面碎屑物质进行暴露测年研究的可行性,可望为较老冰川地貌暴露测年研究提供新的思路。     

岗日嘎布玉东曲末次冰消期冰川演化及其10Be暴露测年研究

末次冰盛期（Last Glacial Maximum, LGM）结束后,全球经历末次冰消期进入全新世,这代表了过去十万年以来最为显著的气候转型事件。末次冰消期的开始在全球范围内近乎同步,但其背后的气候驱动机制仍不明确。中低纬度,如青藏高原及其周边地区的山地冰川对气候变化响应敏感,准确限定LGM结束前后冰川地貌的时代可为上述问题的解决提供可靠的古冰川信息。然而,目前青藏高原仍缺乏足够有针对性的研究。本文选取位于青藏高原东南部的岗日嘎布作为研究区,对该区格泥峰东侧的玉东曲谷口分布的冰碛垄序列进行了详细的地貌调查和宇宙成因核素¹⁰Be暴露测年研究。采自玉东曲谷口附近6道冰碛垄中地貌相对年代较老的4道冰碛垄的14个冰川漂砾¹⁰Be暴露年龄介于（13.3±1.0）~（19.3±1.4） ka。利用累积概率密度和简化卡方等统计分析方法排除异常值后,将这4道冰碛垄中地貌相对年代较年轻两道的形成时代限定为（17.0±0.5） ka和（18.4±1.0） ka,分别对应末次冰消期和LGM后期。与气候记录进行对比后,我们认为这两次冰川波动响应可能受控于印度洋-太平洋暖池海表温度的夏季气温变化。     

中国现代人类起源:来自南方化石地点的年代学证据

现代人类起源的时间和地点是当前古人类学研究和争议的热点。文中评述了 2 0多年来第四纪测年技术取得的进展及其对现代人类起源研究的影响。基于新生碳酸盐岩铀系测年 ,研究了中国南方柳江人洞等多个晚期人类化石地点的年代 ,结果远大于原认为的 2 0～ 30ka。晚期智人在中国出现的时间很可能不晚于西亚和南非 ,中国 4 0～ 1 0 0ka间人类化石的“缺环” ,很可能只是测年技术系统误差造成的假象。上述年代学新证据不支持中国现代人类全部来自非洲的假说。对岩溶洞穴遗址进一步的综合研究 ,有可能为破解有关现代人类起源的诸多疑点提供重要的以至一锤定音的证据     

核电的昨天、今天和明天

25年前的4月26日1时23分,前苏联切尔诺贝利核电站4号机组失火,随后爆炸,最终导致核泄漏。苏联当时派遣超过50万人抢险和清理周边区域,最终利用混凝土等材料建造“石棺”,封存4号机组。负责指挥“石棺”建造工作的波恰科夫将军曾评价说,“石棺”是一座忠烈祠,也是一块墓碑。令人深思的是,在斯拉夫语中,切尔诺贝利意为“死亡与黑暗之神的居所”。如今,死亡之神又走出居所——据报道,近日发现“石棺”出现破裂,放射物又走进人类的噩梦。 从切尔诺贝利到日本福岛核电站,关心人类安危的人们重新审视核电——它的昨天、今天和明天是什么？     

碎屑颗粒磷灰石裂变径迹法在制约地层年龄中的应用

碎屑颗粒热年代学是 2 0世纪 80年代以来发展起来的一种热年代学方法 ,在地质研究中应用广泛。本文以西秦岭地区三岔—四店一带的白垩纪地层为例 ,说明该方法在制约地层年龄中的应用。结果表明这一带的白垩系地层沉积于晚白垩纪 ,或至少含有晚白垩纪的沉积。     

继承性宇生核素对暴露测年结果影响的定量分析方法探讨

宇生核素暴露测年过程中,通常假设在样品最后一次暴露前,样品中的宇生核素（继承性宇生核素）浓度为0。然而,大量的测年数据研究发现,样品的暴露年代结果会受到继承性核素的影响从而高估地貌的真实年代。因此,如何降低继承性核素对暴露年代结果的影响或者定量分析继承性核素的影响程度不仅可为地貌演化提供准确的年代数据,而且对宇生核素暴露测年技术的研究具有重要意义。因此,本文以宇生核素暴露测年技术在冰川地貌中应用为例,通过分析继承性核素的研究概况,并结合宇生核素暴露测年原理,探讨继承性核素对测年结果影响的定量分析方法。研究结果表明： ① 通过样品中 n ( 26 Al)/ n ( 10 Be) 值\[即同一样品中宇生核素Al 26 与Be 10 浓度（单位为atom/g）的比值\]以及同一地貌位置多个的样品年代数据分布情况可初步判断测年结果是否受到继承性核素的影响;② 通过现代冰川冰碛物中宇生核素的浓度可以定量分析继承性核素对暴露测年结果的影响; ③ 通过计算冰碛垄顶部和一定深度（＞2~3 m）样品的宇生核素浓度差,可以减少继承性核素的影响。本研究内容对冰川地貌宇生核素暴露测年具有重要意义。     

迎接寒武系全球年代地层的新划分——2004年版“国际地层表”述评

评述了国际地层委员会最新公布的2 0 0 4年版“国际地层表”的寒武系部分,包括它的底界全球层型和点位的确定和存在的问题、寒武系当前的再划分情况、芙蓉统和排碧阶及其底界全球层型剖面和点位、寒武系的时代跨度。介绍了全球寒武系年代地层的研究方向和正在表决中的全球寒武系最新划分方案。讨论了与我国寒武系年代地层的划分和建立地方性、区域性年代地层系统的相关问题     

成都金堂李家梁子M23号墓石棺构件矿物组成及风化机理研究

成都金堂李家梁子M23号墓出土的汉朝石棺存在表面粉化、剥落等病害现象,急需保护修复。现场调查表明,该石质文物风化病害主要表现为裂隙状风化、页片状风化、粒状风化、粉末状风化等。本文借助X射线衍射(XRD)、偏光显微镜、扫描电镜等对金堂石质文物进行了微观成分及结构分析。结果表明,文物材质为红色砂岩,其碎屑物主要为石英、钠长石、岩屑和少量云母,胶结物以钙质为主,含少量的炭质及泥质。该砂岩产生风化病害的主要原因是钙质胶结物的溶解流失及泥质胶结物遇水的崩解,同时还受岩屑、长石类碎屑风化蚀变的影响。该研究可为石棺的后期保护修复工作提供基础科学数据。     

碎屑沉积岩沉积作用的高精度定年——自生磷钇矿离子探针UPb年龄测定

沉积岩沉积作用准确时间的厘定是目前同位素年代学研究中的一大难题 ,尽管目前可采用多种方法对成岩过程中的自生矿物进行定年 ,但由于技术上的原因 ,这项研究一直发展很慢。文中详细介绍了近年来发展起来的运用高精度离子探针 (SHRIMP)技术确定自生磷钇矿形成年龄 ,进而确定沉积作用年代的新方法。如 ,澳大利亚西北部Kimberley盆地中未变质的古元古代砂岩中自生磷钇矿的SHRIMP定年将成岩作用限定在 7Ma的误差范围之内。相比之下 ,对非洲南部太古宙Witwa tersrand超群和澳大利亚西南部MountBarren群绿片岩相变质砂岩中磷钇矿的研究 ,不仅确定了所研究岩石的成岩作用时代 ,而且恢复了该区后期的复杂热演化历史。研究还表明 ,这种方法同样适用于显生宙岩石。这些实例表明 ,磷钇矿的SHRIMP定年不仅可以测定从太古宙到第四系所有年代碎屑沉积岩的沉积时代 ,而且可以实现极小尺度上的微区定年 ,从而可以研究岩石自沉积成岩以后的演化历史 ,显示这一方法在沉积作用及相关热事件问题研究上的巨大潜力。     

白云鄂博赋矿地层H8白云岩的U-Pb和Pb-Pb定年

采用U Pb和Pb Pb方法研究了内蒙古白云鄂博赋矿H8白云岩的年代。U Pb体系不能给出等时线 ,因为体系中铀显著过剩 ,显示了铀的近代加入。Pb Pb等时线 ,得到中元古约 15 0 0± 40 0Ma的Pb Pb年龄 ,并经过了约 82 0± 370Ma的后期扰动。白云鄂博赋矿H8白云岩的成岩年代在中元古代 ,在晚元古代或古生代发生了后期扰动。     

Radiometric dating of the Middle Palaeolithic tool industry and associated fauna of Pin Hole Cave,Creswell Crags,England

Uranium-series dating of derived speleothem suggests that the sediments enclosing a Middle Palaeolithic stone artefact assemblage in Pin Hole Cave probably accumulated after about 64 ka, and ¹⁴C dates indicate a likely age of > 40 ka for the large mammal fauna associated with it. Electron spin resonance data from the fauna conform with these age constraints and are consistent with accumulation between 38 and 50 ka. This evidence supports the view that Britain was recolonised by hominids during Oxygen Isotope Stage 3. Stratigraphically higher stone tool industries demonstrate the local presence of both early Upper and late Upper Palaeolithic cultures. © 1998 John Wiley & Sons, Ltd.     

Diagnostics,deterioration and provenance of stone materials from the Jefferson Page tomb (Non-Catholic Cemetery of Rome,Italy)

The monumental tomb of Jefferson Page, an officer in the American Navy, was built in 1899 and is located in the Non-Catholic Cemetery of Rome (Italy). This study presents complementary diagnostic studies characterizing the stone of the tomb and the weathering and decay phenomena it has undergone. The monument is made of a single type of whitish marble, variously veined and often covered with black patinas. Petrographic, isotopic and LA-ICP-MS analyses attribute the marble to the Carrara district. SEM/EDS and microbiological analyses indicate that the black patinas are due to cyanobacterial autotrophic and fungin heterotrophic colonization. Fourier-transform infrared spectroscopy revealed the presence of organic material on some portions of the tomb, due to undocumented restoration carried out with a mixture of marble powder and a polyester resin.     

河北张家口水泉沟岩体SHRIMP年代学研究及其意义

采用先进的 SHRIMP测年技术对河北水泉沟碱性杂岩体进行了年龄测定，获得东坪金矿区水泉沟岩体二长岩锆石 U- Pb年龄为 (390± 6)Ma，后沟金矿区水泉沟岩体正长岩年龄 (386± 6)Ma，比较可信地确定了水泉沟岩体的成岩时代为晚加里东期—早海西期。这表明北部温都尔庙-西拉木伦河加里东俯冲造山运动强烈地影响本区，水泉沟岩体是这次运动的产物。根据前人测得的东坪和后沟金矿床蚀变围岩钾长石的 Ar- Ar和 K- Ar年龄，金矿化的时代是中生代燕山期，与岩体的成岩年龄有 200 Ma的时差，成因上可能与碱性杂岩体关系不大，因此，东坪和后沟等金矿床可能不属于碱性岩型金矿床。     

Stone run (block stream) formation in the Falkland Islands over several cold stages,deduced from cosmogenic isotope (10Be and 26Al) surface exposure dating

Cosmogenic isotope (¹⁰Be and ²⁶Al) surface exposure dating has been applied to valley‐axis and hillslope stone runs (relict periglacial block streams) and their source outcrops in the Falkland Islands, South Atlantic. The data indicate that stone runs are considerably older landforms than previously envisaged and afford no evidence that they are a product of the Last Glacial Maximum; the samples range in apparent ¹⁰Be age from 42k to 731k yr BP, but some of these are minima. The results indicate that valley‐axis stone runs may be up to 700–800k yr old, have simple exposure histories and are composite landforms that developed over several cold stages. Analyses of some hillslope and outcrop samples also demonstrate simple exposure histories with ¹⁰Be ages from 42k to 658k yr BP. In contrast, isotopic ratios from other hillslope and outcrop samples reveal they have had a complex exposure history involving periods of burial or shielding; the samples range in ¹⁰Be age from 59k to 569k yr BP and these are regarded as minimum age estimates. Larger stone runs may be older than smaller runs and there is a possibility that stone runs older than 800k yr exist in other parts of the Falklands. The assertion that glaciation in the Falklands was restricted to the highest uplands is supported by the data, and the potential for age determination of other boulder‐strewn and bedrock landforms, using cosmogenic isotope analysis, in order to extend the geochronology of Quaternary events and processes is noted. Copyright © 2008 John Wiley & Sons, Ltd.     

漳州盆地水热系统氚同位素研究

本文依据26个天然水样品的氚同位素测试数据,分析了漳州盆地地下热水及其它天然水的氚值特征及其形成条件;利用“活塞模型”方法计算了漳州盆地地下水和地下热水的年龄;为弄清全盆地地下水的补给、迳流和排泄的总体格局和揭示地下热水的成因提供了依据。     

Petrologic, isotopic, and radiometric age constraints on the origin and tectonic history of the Malino Metamorphic Complex, NW Sulawesi, Indonesia

The Malino Metamorphic Complex (MMC) is located at the western end of the north arm of Sulawesi. It consists of mica schists and gneisses (derived from proximal turbidite and granitoid protoliths), with intercalations of greenschist, amphibolite, marble, and quartzite, forming an E-W elongated dome-like structure bounded on all sides by faults. The age of the MMC is constrained between Devonian and Early Carboniferous. This Paleozoic age, the presence of Archean and Proterozoic inherited zircons, and the isotopic signature of the mica schists and gneisses indicate that the terrane was derived from the New Guinea-Australian margin of Gondwana. Similarities with basement rocks in the Bird’s Head suggests a common origin. Greenschists forming a discontinuous selvage (metamorphic carapace) around the complex were derived from adjacent autochthonous Paleogene formations. The rocks of the MMC show a Barrovian-type progression from greenschist through epidote-amphibolite to amphibolite facies. P–T estimations suggest a depth of burial of up to 27–30 km. K/Ar and 40Ar/39Ar cooling ages of 23–11 Ma, and a 7 Ma age for unconformably overlying volcanic rocks, indicate that the complex was exhumed during the Miocene. Two tectonic scenarios are considered: 1. the continental fragment docked with Sulawesi during the Mesozoic and was exhumed as a metamorphic core complex during the Miocene; 2. it was subducted beneath the north arm during the late Oligocene and then rapidly returned back to the surface.     

关于含柯石英锆石SHRIMP测年获得大别-苏鲁超高压变质带超高压变质作用年龄的讨论

对大别一苏鲁超高压变质(UHPM)带部分含柯石英包体的锆石及部分进行SHRIMP U—Pb测年的锆石进行划分和讨论后得出为大别-苏鲁UHPM带超高压变质作用(UHPM)年龄而进行含柯石英锆石SHRIMP U—Pb测年．宜从有结晶环带且在环带域或环带核部有柯石英包体的锆石的核部或环带域进行SHRIMP U—Pb测年．不宜从锆石边部获得UHPM年龄。着重讨论杨经绥等(2002)的两颗含柯石英锆石的结构，柯石英包体所在部位。测年数据的意义，得出苏鲁UHPM带UHPM年龄是578Ma(或略大于578Ma)。且这一认识与苏鲁UHPM带内区域地质情况相吻和。锆石中(多在边部)给出的印支期年龄值反映印支期地质作用(流体改造、重结晶等)改造事件的时代。     

北山明水地区花岗岩时代的确定及其地质意义

在详细的野外地质调查研究基础上，采用高精度的^40Ar-^39Ar测年技术，对北山明水地区大面积分布的花岗岩类岩体进行了同位素年龄测试，确定其为印支期侵入体。该岩体时代的准确界定，说明印支期构造-岩浆活动对北山地区的大地构造格架产生了十分重要的影响，它可能是由塔里木板块与哈萨克斯坦板块最终碰撞对接引起的。     

The I-Xe chronometer

¹²⁹Xe, from the decay of the now-extinct 16.7 Ma¹²⁹I, accumulates in iodine-bearing sites and since most iodine host phases are secondary, the I-Xe system is typically a chronometer for post-formational processes. The validity of the I-Xe chronometer is confirmed by comparison with Pb-Pb ages on phosphate and feldspar separates from twelve meteorites. Phosphate separates are found to be concordant with Pb-Pb for all six samples in which useful I-Xe data were obtained. Feldspar is a better iodine host than apatite in H chondrites, typically providing good I-Xe isochrons. These too are concordant with the Pb-Pb ages of the corresponding phosphates for five out of six feldspar separates. The exception is Allegan whose feldspar yields one of the oldest I-Xe ages observed, similar to those for CI and CM magnetites. We attribute this to a more primary mineralization, predating the secondary phosphate from which the comparison Pb-Pb age was obtained. Absolute I-Xe ages, found using the reported Pb-Pb age of Acapulco phosphate provide an absolute I-Xe age of 4.566 ± 0.002 Ga for both Shallowater and Bjurböle irradiation standards. This allows relative I-Xe ages to be interpreted in the context of absolute ages.     

Electron spin resonance dating of Quaternary bone material from Tasmanian caves—A comparison with ages determined by aspartic acid racemization and C14

Abstract

Fourteen bone samples are analysed to test the usefulness of equivalent dose (ED) determinations by electron spin resonance (ESR) as a rapid method of determining relative age and making an estimate of absolute age. ED values are compared with eight aspartic acid dates and two C¹⁴ dates. The latter are dates on charcoal found in close association with bone at archaeological sites. For samples less than 25 000 years old an excellent correlation is obtained when ED values are compared with dates obtained by the other two methods. The relationship suggests that ED values can be converted to estimates of bone age by assuming a mean annual dose rate of 0.1 rad/yr. Age determinations provide little evidence to support earlier suggestions that elements of the Late Pleistocene megafauna survived until the end of the Pleistocene. Bone material at some sites in the‐Florentine Valley and near Montagu appears to be much older than had previously been believed. Only one site (Main Cave, Montagu) containing megafaunal elements appears to be terminal Pleistocene in age but the possibility of reworking of megafauna material from nearby older sites cannot be excluded. ESR dating has considerable potential as an exploratory dating tool but can only be applied to dense, unaltered bone samples. Attempts to analyse five samples from Kutikina Cave in Western Tasmania were unsuccessful because of post‐depositional contamination of the bone.