Episodic exhumation of accretionary complexes: Fission-track thermochronologic evidence from the Shimanto Belt and its vicinities, southwest Japan

Abstract Apatite and zircon fission-track (FT) analyses of the Shimanto accretionary complex and its vicinities, southwest Japan, unraveled the episodic material migration of the deep interiors of the accretionary complex. Apatite data with 100°C closure temperature (T_e) generally indicate ~10 Ma cooling throughout the Shimanto complex. In contrast, zircon data with 260°C T_e exhibit a wide range of apparent ages as a consequence of paleotemperature increase to the zircon partial annealing zone. In the Muroto and Kyushu regions, maximum temperatures tend to have been higher in the northern, older part of the complex, with indistinguishable temperature differences between coherent and melange units adjacent to each other. It thus suggests, along with vitrinite reflectance data, that older accretionary units occurring to the north sustain greater maximum burial during the accretion-burial-exhumation process. Zircon data suggest two cooling episodes: ~70 Ma cooling at widespread localities in the Cretaceous Shimanto Belt and Sambagawa Belt, and ~15 Ma cooling in the central Kii Peninsula. The former is consistent with ⁴⁰Ar/³⁹Ar cooling ages from the Sambagawa Belt, whereas the latter slightly predates the widespread 10 Ma apatite cooling ages. These data imply that the extensive material migration and exhumation took place in and around the Shimanto complex in Late Cretaceous as well as in Middle Miocene. Considering tectonic factors to control evolution of accretionary complexes, the episodic migration is best explained by accelerated accretion of sediments due to increased sediment influx at the ancient Shimanto trench, probably derived from massive volcano-plutonic complexes contemporaneously placed inland. Available geo- and thermochronologic data suggest that extensive magmatism triggered regional exhumation twice in the past 100 Ma, shedding new light on the cordilleran orogeny and paired metamorphism concepts.     

鄂尔多斯盆地下古生界地层地史模拟与油气聚集

根据沉积压实原理，应用“反剥离模式”恢复盆地内各地层层系在不同地质历史时斯的古厚度及古埋深，并得到陶系柄部风化剥蚀面的一系列时间－埋深平面图及单井埋藏史图，由此对盆地下古生界奥陶系顶面的加里东期古风化剥蚀面的构造演化规律作出定量分析，结合盆地的生、排烃史研究成果，分析预测盆地内古古生界的油气聚集规律，为油气勘探与部署提供定量依据。     

克拉通内盆地研究中的几个重要问题

克拉通内盆地不仅记录了克拉通在显生宙的演化历史，而且是油气富集的重要场所。本文提出了在克拉通内盆地研究中的几个重要问题：（１）克拉通内盆地基底的非均一性；（２）克拉通内盆地地层层序及其边界不整合分析；（３）克拉通内盆地沉降史分析；（４）克拉通内盆地成因探讨；（５）克拉通内盆地演化与板块构造作用的关系。通过对这些问题的研究，可以深入理解克拉通内盆地形成、充填、改造作用及其对油气分布的控制。     

镜质组反射率与沉积盆地古地温分析

在地质研究与资源勘探中，特别是针对油气生成、运移和保存有关的地热过程分析，镜质组反射率（Ｒ）已被广泛地应用于沉积盆地古地温的确定。本文从Ｒ增值的反应动力学、Ｒ－古地温－受热时间模拟计算、流体扰动对流型热体系中的Ｒ性征及Ｒ古地温分析技术扩展等方面，概括地总结讨论了有关应用现状与理论进展。由于沉积有机质构成及其热反应作用的复杂性，过分简单地将Ｒ与地温值对应的做法已被否定，代之以地质、地球热力学与反应动力学的综合分析。不同源岩中Ｒ增值与热能关系的确定，温度－时间计算方法的改进、异常热背景如对流型热体制的分析以及低成熟与镜质组缺失条件下成熟度参数的Ｒ标定等，将是今后急待解决的主要问题。     

库车坳陷沉降与天山中新生代构造活动

位于塔里木盆地北缘、天山南侧的库车坳陷为中新生代发育的构造单元。坳陷与天山造山带在成因上紧密相连，坳陷的沉降是由于天山山体隆升扩展引起的岩石圈挠曲响应。根据纵横向不同位置盆地沉降史的分析对比，该坳陷为典型的挤压盆地。推测中生代时期天山造山带以走滑和逆冲作用为主，新生代时期至少在库车坳陷北缘，天山造山带以向南冲断作用为主。库车坳陷强烈沉降时期并不对应于粗碎屑沉积，而对应于细碎屑沉积时期，即天山造山带构造强烈活动时期。天山造山带强烈活动造成库车坳陷强烈沉降，其主要原因与塔里木板块南侧的羌塘地体、拉萨地体、科西斯坦杂岩和印度次大陆的增生碰撞有关。     

章鸿钊在中国地质学史上的贡献及其科学史意义

中国地质学会第一任会长章鸿钊先生早年留学日本攻读地质学期间，萌生了创立中国地质事业和地质调查机构的设想，并将世界发达国家地质科研机构的情况介绍到中国。回国后，章鸿钊先生着手中国地质事业起步的规划和地质调查机构的设计，并在规划实施阶段做出卓越的贡献。按照章鸿钊的思路创建的中国地质调查所是中国现代科学起步阶段的里程碑。章鸿钊先生自幼国学功底深厚，在身体状况限制了野外地质调查的中年和晚年时期，他专注地质与矿产方面的古籍考证和整理，并将考证结果与地质科学知识相结合，撰写了《石雅》、《古矿录》、《三灵解》等一批论著。章鸿钊先生晚年提出了与燕山运动有别的自中生代晚期至始新世后的震旦运动。     

隔震技术在高烈度区剪力墙结构中的应用研究

对于近断层处高烈度区高层剪力墙结构，传统设计难以解决墙体太厚、配筋太大等难题。为研究在考虑近断层影响下高烈度区剪力墙住宅采用隔震设计的技术可行性，采用隔震设计对某剪力墙结构工程进行全面分析。对比分析常规剪力墙结构方案及增设橡胶隔震支座的隔震方案，分析结果表明，隔震方案较常规方案前3阶结构自振周期延长约3倍，从而有效减小了上部结构的地震作用；在设防烈度地震作用下，结构水平向减震系数为0.281，上部结构所受水平地震作用和抗震措施可按降低一度进行设计；罕遇地震作用下隔震支座性能稳定，上部结构基本处于弹性工作状态。研究结论可为隔震支座设计和进一步研究提供参考。     

Studies of Cainozoic environmental change in Tasmania and coastal East Antarctica: a review

Observational studies on Cainozoic environmental changes in both Tasmania and East Antarctica have led to important modifications in the accepted interpretation of the history of glaciation for each area. Many contributors have played an important role in the processes of investigation leading to the present state of knowledge. A crucial role has been played by the integration of the methods of glacial geomorphology, stratigraphy, sedimentology and dating methods. From studies based on combinations of these approaches, a model of multiple glaciations has been developed to explain observed features in Tasmania. This model is complemented by studies of vegetation history, largely through pollen analysis. A less complete picture of the history of ice‐sheet fluctuations in East Antarctica is beginning to emerge from similar applications of cross‐disciplinary studies.     

The Triassic of the Thakkhola (Nepal). II: Paleolatitudes and comparison with other Eastern Tethyan Margins of Gondwana

During the Triassic, the Thakkhola region of the Nepal Himalaya was part of the broad continental shelf of Gondwana facing a wide Eastern Tethys ocean. This margin was continuous from Arabia to Northwest Australia and spanned tropical and temperate latitudes.A compilation of Permian, Triassic and early Jurassic paleomagnetic data from the reconstructed Gondwana blocks indicates that the margin was progressively shifting northward into more tropical latitudes. The Thakkhola region was approximately 55° S during Late Permian, 40° S during Early Triassic, 30° S during Middle Triassic and 25° S during Late Triassic. This paleolatitude change produced a general increase in the relative importance of carbonate deposition through the Triassic on the Himalaya and Australian margins. Regional tectonics were important in governing local subsidence rates and influx of terrigenous clastics to these Gondwana margins; but eustatic sea-level changes provide a regional and global correlation of major marine transgressions, prograding margin deposits and shallowing-upward successions. A general mega-cycle characterizes the Triassic beginning with a major transgression at the base of the Triassic, followed by a general shallowing-upward of facies during Middle and Late Triassic, and climaxing with a regression in the latest Triassic.     

鄂尔多斯地块早古生代构造格局及演化

本文通过沉积、构造和沉降历史的综合分析，揭示了鄂尔多斯早古生代碳酸盐岩台地演化历史，恢复了不同演化阶段的古构造格局，并探讨了古构造的演化机制。