东北印度洋源汇过程及古环境与古季风演化

东北印度洋地理位置独特,其沉积物记录了青藏高原隆升及孟加拉扇的“源-汇”过程、印度季风与东亚季风的“海-气”交互作用、印-太暖池热传输的演变与高纬气候之间的相位关系等关键信息,是喜马拉雅地区“构造-气候-沉积”耦合演化的良好记录载体,是探讨多圈层相互作用、探索古气候与古环境演化的理想“窗口”。本文系统总结了近年来有关东北印度洋季风与表层环流特征、沉积物组成及物源、气候环境演化以及环境磁学记录等方面的研究进展。分析表明,东北印度洋为典型的季风风场,表层环流受季风影响强烈,夏季和冬季环流差异明显。沉积物类型丰富,包括河流输运而来的陆源碎屑、钙质和硅质为主的生物沉积以及火山物质等。但目前对于该区域的沉积物的具体组成、“源-汇”过程、迁移历史、季风演化与青藏高原隆升、高纬气候变化之间相互关系等方面的认识尚存在较大的分歧。同时,受样品获取难度大、磁学信号稀释严重等因素的限制,环境磁学作为一种在示踪沉积物物质来源、恢复古气候和古环境等方面被普遍认可的技术手段,在东北印度洋区并没有得到充分的发挥与应用。因此,未来需要在前人研究的基础上,将目光向东北印度洋更南、更深处延伸,对其“源-汇”过程进行全面分析。在研究方法上进一步拓展,采用更高精度的技术手段提取磁学信号,加大环境磁学的应用,寻找有效的替代性指标,解决该地区季风演化、古海洋环境变化等气候环境问题,为该地区环境气候研究提供新认识。并尝试开展地磁场长期变化(paleosecular variation, PSV)研究,建立东北印度洋的PSV记录,辅助修正全球地磁场模型,探究地球深部动力过程。     

Luminescence and ESR dating of the sedimentary infill from the multi-level cave system of Alkerdi-Zelaieta (Navarre,N Spain)

The finding of Upper Paleolithic engravings in 2016 triggered a multidisciplinary investigation of the Alkerdi cave system (Urdazubi, N Spain). The study of the speleogenetic processes led to the identification of at least 6 paragenetic cave levels with associated sedimentary infill. In order to unravel the timing of changes in the karst dynamics and to get some insights about sediment origin, two sediment samples were collected from cave levels 4 and 1 for numerical dating purpose, using both Optically Stimulated Luminescence (OSL) and Electron Spin Resonance (ESR) methods. One additional modern-age sample was also taken from the entrance of the karst to evaluate the magnitude of the optical bleaching achieved by the quartz grains before entering the cave system. Last, one sample was collected from a flowstone for U-series dating, providing independent age control.OSL measurements were carried out using small quartz multi-grain (MG) and single-grain (SG) Single Aliquot Regenerative-dose (SAR) protocol. Initial Equivalent Dose (D_e) results show evidence of saturated OSL signal for the sample of the higher level (with ∼60% of saturated aliquots). Unlike SA data, SG analyses do not meet the usual quality criteria (e.g., relatively high recuperation ratios, only a few grains with useable signal), suggesting that corresponding dating results should be treated with caution.Hence, both MG and SG TT-OSL and MG ESR methods were subsequently employed, as the corresponding signals are known to have higher saturation levels than OSL ones. ESR analyses were based on the Multiple Centre (MC) approach using the standard multi-grain multi-aliquot additive (MAA) dose method, while TT-OSL measurements were performed following Demuro et al. (2020). The latter, however, did not return any useful results for both samples. MC ESR data show the usual D_e pattern (D_e(Al)>D_e(Ti op. D)>D_e(Ti–H)) indicating that among the three ESR signals analyzed, the Ti–H most likely provides the closest estimate to the true burial age. However, low measurement repeatability and goodness-of-of fit indicate that the reliability of the ESR results may be reasonably questioned.Results derived from this multi-technique dating approach provide the first chronological constraints for the sedimentary infill of the Alkerdi cave system. In particular, they suggest that sediment deposition in Cave Level 4 (ALK-OSL01) occurred around 130 ka, which is in good agreement with the minimum age constraint given by the speleothem (80.5 ± 9.0 ka). In comparison, the young age obtained for sample ALK-OSL02 (5.0 ± 0.9 ka) suggests recent Holocene formation of the lowest cave level 1.Finally, the MG De value obtained for the modern sample is close to zero (<1 Gy), indicating that the OSL signal is almost fully reset at a multi-grain level before entering the cave. Additionally, despite the large De overdispersion measured in this modern sample, the De values are one to two order of magnitude lower than those obtained with the same model in the other two samples. Therefore, the large OSL D_e overdispersion (OD) values of up to 64% obtained for the two samples from Cave Level 4 and 1 are most likely related to re-sedimentation processes inside the cave system.     

内蒙古额尔古纳红水泉地区奥陶系乌宾敖包组沉积时代及物源区分析:碎屑锆石U-Pb年代学,Lu-Hf同位素地球化学证据

选取内蒙古额尔古纳红水泉地区奥陶系乌宾敖包组石英砂岩进行碎屑锆石U-Pb年龄、原位Lu-Hf同位素研究,尝试限定该地层形成时代及碎屑物质来源,并探讨其沉积大地构造环境。结果显示,采自该地层的2个砂岩样品中的碎屑锆石多数发育典型的岩浆振荡生长环带,呈自形–半自形且具有较高的Th/U值(0.12~1.63),均暗示它们多数为岩浆成因。结合微量元素特征及稀土元素配分模式图,认为碎屑锆石寄主岩石应为花岗质杂岩体。2个砂岩样品具有相似的年龄和Hf同位素组成,锆石年龄分布大致可分为3个主要年龄区间:(1)440~540 Ma,主峰值年龄约为492 Ma和506 Ma,次峰值年龄为447 Ma;ε_Hf(t)值介于?2.77~+11.73之间,Hf的两阶段模式年龄为680~1636 Ma;(2)750~950 Ma,主峰值年龄为805 Ma,次峰值年龄为825 Ma和961 Ma;ε_Hf(t)值介于?1.14~+11.43之间,Hf的两阶段模式年龄为1100~1824 Ma;(3)1700~2000 Ma,峰值年龄为1787 Ma;ε_Hf(t)值介于?9.18~?2.75之间,Hf的两阶段模式年龄为2682~3016 Ma。所有样品碎屑锆石ε_Hf(t)值为?9.18~+11.73,Hf的两阶段模式年龄为680~3016 Ma,大部分锆石的Hf同位素组成集中于球粒陨石与亏损地幔标准线之间,表明沉积物源以早古生代和新元古代新增生地壳物质为主,同时存在少量中元古代晚期古老地壳物质的活化改造。结合前人已报道的邻区相关岩体年代学及地球化学资料,研究区乌宾敖包组的沉积时代不早于晚奥陶世,沉积物主要来自额尔古纳和兴安地块的近缘碎屑物,其形成与早古生代时期古亚洲洋演化过程中额尔古纳与兴安地块碰撞拼贴以及随后的伸展垮塌相关。     

赣南西华山成矿花岗岩锆石U-Pb年代学和Hf同位素特征及其地质意义北大核心CSCD

赣南西华山钨矿是与侏罗纪花岗岩有关的大型石英脉型矿床,也是我国南岭成矿带赣南地区典型的钨矿床。本文选取西华山钨矿成矿花岗岩进行了锆石LA-ICP-MS U-Pb定年、微量元素和Hf同位素分析,旨在揭示花岗岩的形成时间并推断岩石成因及其对成矿的指示。锆石U-Pb测年结果表明,西华山中粒黑云母花岗岩锆石206 Pb/238 U加权平均年龄为154.8±6.0 Ma。锆石形态、激光拉曼和地球化学特征表明,该花岗岩受到岩浆热液的影响。锆石的176 Yb/177 Hf和176 Lu/177 Hf比值较高,表明源岩浆有强烈的流体出溶作用。西华山黑云母花岗岩的εHf(t)变化范围较小,呈明显负值(-12.8~-10.8),且集中在华夏地块古老基底范畴内,指示其形成于古老地壳物质的部分熔融。     

中国沙漠物源研究:回顾与展望

沙漠物源研究不仅在风沙地貌学上有重大的理论和实践意义,而且对联结大气粉尘排放、黄土堆积、气候系统和海洋生物地球化学循环也有重要价值。在简要回顾中国沙漠研究的基础上,梳理了中国沙漠物源研究的理论、方法和主要成果,结合国际上沉积物物源分析的趋向,指出目前世界沙漠物源的研究都是基于沉积物组份属性统计的反演模型,这种研究范式在数据获取、处理与解释方面存在缺陷,如沉积物的取样设计与测试分析、未消除"粒级依赖"对沉积物组份影响、数据未进行对数变换、忽视Dickinson图解应用的前提条件等。提出今后中国沙漠物源研究的方向:①采用正确统一的取样设计和分析方法对各沙漠的沉积物组份属性进行系统研究,建立中国沙漠沉积物组份的属性数据库;②选择若干典型沙漠,利用其周边山地详尽的地质构造、母岩和气候数据,定量构建沉积物生成的正演模型,模拟源区生成沉积物的数量、成分和结构,并用建成的沉积物组份属性数据验证和校正;③定量评估河流冲积物、冲积-湖积物、洪积-冲积物和基岩风化的残积、坡积物对中国各沙漠物源的贡献率与迁移路径,研究中国各沙漠中细颗粒物质的形成机制,对比中国沙漠与低纬度沙漠物源的形成机制;④定量研究历史和地质时间尺度沙漠-黄土-深海沉积物物源的内在联系及其驱动因素,建立陆地-大气-海洋物质循环的机理模型。     

渤中西环古近系东营组物源转换与沉积充填响应

通过砂岩中碎屑锆石U-Pb年龄分析、火山碎屑组分含量变化、地震多属性分析、层序地层格架与沉积充填特征综合分析,认为东二段沉积时期渤中西环的物源供给方式、层序地层格架及沉积充填特征发生明显的变化.东二下段沉积期前,湖盆处于强烈裂陷期,中-深湖相泥岩发育,物源主要为盆地内部的中生代火成岩基底,沉积层序明显受盆内低凸起控制,在盆内低凸起四周发育一系列近源的扇三角洲朵体;东二下段沉积期后,湖盆处于断-坳过渡期,盆内低凸起四周的断裂活动减弱,沉积层序逐渐向盆内低凸起超覆,盆外太古代-元古代变质岩物源供给不断加强,近源的扇三角洲砂体逐渐向远源的辫状河三角洲砂体转化,同时发育宽广的滨浅湖环境.渤中西环古近纪沉积充填过程中,地层样式、沉积模式与物源供给方式的一致性变化,体现了裂陷湖盆充填演化的内在规律,为我国东部裂陷盆地演化及裂陷旋回划分提供了新的线索.     

北秦岭柳叶河盆地石炭系—二叠系含砾砂岩碎屑锆石LA-ICP-MS U-Pb年龄及其地质意义

通过北秦岭黑河地区柳叶河盆地碎屑锆石年龄研究,探讨盆地沉积物年龄结构,并进一步推断其物源及与秦岭造山带的盆山耦合过程。采自柳叶河盆地石炭系—二叠系含砾砂岩样品中的82颗碎屑锆石年龄可分为6组:260~542Ma、800~1100Ma、1320~1560Ma、1640~2250Ma、2300~2660Ma和2720~2870Ma。其中260~542Ma年龄段所占测点比例最大,占锆石总数的31%,其次为1640~2250Ma、2300~2660Ma和800~1100Ma年龄段。最老年龄值为2834±40Ma,最年轻者为264±5Ma。从碎屑锆石年龄结构对比及石炭纪地层交错层理推断,柳叶河盆地石炭系—二叠系物源区主要为当时的北秦岭山地。此外,碎屑锆石年龄结构对比表明,鄂尔多斯盆地南部与柳叶河原始盆地有相同的年龄谱特征,意味着它们具有同一物源区。北秦岭山地是在加里东造山作用后期影响下迅速隆升而形成的。其后,随着南侧勉略洋的打开,华北地台相对沉降及沿商丹带的走滑断陷使柳叶河盆地出现,仍旧处于隆升状态的北秦岭山地开始作为该盆地及其北侧鄂尔多斯盆地南部的主要物源区。     

The Reliability of Assigned Values from the GeoPT Proficiency Testing Programme from an Evaluation of Data for Six Test Materials that have been Characterised as Certified Reference Materials

Assigned values derived from the GeoPT proficiency testing programme were compared with certified values for six certified reference materials that have been used as test materials in the GeoPT programme. Statistical analysis showed that there were few significant differences between these sets of data and that these differences had no significant impact on the GeoPT assessment when fitness‐for‐purpose criteria were taken into account.     

BOOK REVIEWS

Books reviewed in this article: Boundary Control and Legal Priniciples . Curtis M. Brown , Walter G. Robillard and Donald A. Wilson . Lost Initiatives: Canada's Forest Industries, Forest Policy, and Forest Conservation . R. Peter Gillis and Thomas R. Roach . The Navajo Atlas: Resources, People, and History of the Dine Bikeyah . James M. Goodman . The City and the Sign . M. Gottdiener AND Alexandros Ph . Lagopoulos , EDS. The Comfortable House: North American Suburban Architecture 1890–1930 . Alan Gowans . Arabic-Islamic Cities. Building and Planning Principles . Besim Salim Hakim . Contemporary Climatology . Ann Henderson -Sellers and Peter J. Robinson . A Trace of Desert Waters . Samuel G. Houghton . Geography, Resources and Environment. Vol. 1: Selected Writings of Gilbert F. White. Vol. 2: Themes from the Work of Gilbert F. White . Robert W. Kates AND Ian Burton , ED. Spatial Dimensions of Unemployment and Underemployment (A Case Study of Rural Punjab) . Gopal Krishan . Maps of the Holy Land: Cartobibliography of Printed Maps, 1475–1900 . Compiled by Eran Laor , assisted by Shoshana Klein . The Geography of Third World Cities . Stella Lowder . A Perspective on U.S. Farm Problems and Agricultural Policy . Lance Mc Kinzie , Timothy G. Baker AND Wallace E. Tyner . Soil Erosion and Its Control. R.P.C . Morgan , ED Geopolitics . Patrick O'Sullivan . Landscape, Meanings and Values . Edmund C. Penning -Rowsell AND David Lowenthal , EDS.     

Geochemical discriminations of sandstones from the Mohe Foreland basin,northeastern China: Tectonic setting and provenance

The Mohe region near the border area of China with Russia is in Heilongjiang Province. Topographically the area consists of lower mountains or hills situated at the northern end of the Da Hinggan Mountains. Struc-turally the Mohe basin rests on the north margin of the Ergun Block, and the Mongol-Okhotsk Orogen is lo-cated to the north of the basin. Due to poor access conditions and good vegetation coverage, previous researches on the basin are much weak with few spe-cial geological inves…