Kriging in the Presence of Locally Varying Anisotropy Using Non-Euclidean Distances

A stationary specification of anisotropy does not always capture the complexities of a geologic site. In this situation, the anisotropy can be varied locally. Directions of continuity and the range of the variogram can change depending on location within the domain being modeled. Kriging equations have been developed to use a local anisotropy specification within kriging neighborhoods; however, this approach does not account for variation in anisotropy within the kriging neighborhood. This paper presents an algorithm to determine the optimum path between points that results in the highest covariance in the presence of locally varying anisotropy. Using optimum paths increases covariance, results in lower estimation variance and leads to results that reflect important curvilinear structures. Although CPU intensive, the complex curvilinear structures of the kriged maps are important for process evaluation. Examples highlight the ability of this methodology to reproduce complex features that could not be generated with traditional kriging.     

马元铅锌矿含矿构造带特征及矿床成因讨论

陕西马元铅锌矿产于扬子板块北缘碑坝穹隆构造周缘灯影组上段。矿化受角砾状、裂隙状白云岩和放射状横向断裂组成的构造带控制。矿化强度与构造角砾岩发育程度和藻屑白云岩厚度成正相关。晚震旦世灯影期,通过基底断裂及裂隙通道产生的海水循环系统不断地萃取并吸收基底杂岩中的Pb、Zn等有用组份,运移到台坪相被藻类吸附,铅锌矿初步富集。灯影世末期,基底隆起产生灯影组容矿构造系统,同时形成构造热卤水活化、迁移吸附在藻屑白云岩中的铅锌等成份形成含矿热液,并在容矿构造带中充填富集成矿。     

温盐环流反转及其对新生代气候的影响

温盐环流是由海水温度、盐度差异驱动的全球洋流循环系统。在气候系统中,它对全球热量输送起到了十分重要的作用。在亚轨道尺度(千年时间尺度)上,温盐环流的改变导致了一系列快速的气候变化,因此备受关注。在构造时间尺度(百万年时间尺度)上,古海洋记录和数值模拟揭示出,温盐环流的反转对新生代气候也产生了非常显著的影响。在新生代,温盐环流由“南大洋深层水主控型”向“北大西洋深层水主控型”反转。这一反转改变了全球的热量输送,使得南半球强烈变冷,并有可能导致南极东部永久冰盖的形成。在这一反转事件中,热带海道的作用更加重要。     

The crust and upper mantle of the Sulu UHPM belt

All results from integrated geophysical investigations in the Sulu region are summarized in this paper, trying to reconstruct the Sulu UHPM processes. New seismic S-wave tomographic results suggest a velocity-abnormal zone occurs beneath the Sulu crust, revealing detailed upper mantle structures that high-velocity lumps within the abnormal zone are sequentially distributed beneath the bottom of the asthenosphere. These high-velocity lumps might represent delaminated eclogites or residuals of the subducted oceanic plate. Based on integrated interpretation of the geophysical data, we propose a working model for tectonic reconstruction of the Sulu UHPM processes, which can explain the crust and upper mantle structures of the area. The involved tectonic processes are related to north-eastward escaping of the Sulu terrane, subduction and delamination cycles of the Dabie-Sulu oceanic plate, and post-orogenic lithospheric thinning and magma underplating. The UHPM rocks are believed to have syn-subduction delaminated down to the bottom of the asthenosphere during 245-180 Ma, and the delamination process seemed smooth and nearly continuous without extensive violence.     

吉林省东部韧性剪切带特征及其与金银成矿关系

国内外贵金属与控矿构造研究表明,韧性剪切带,特别是发育在太古宙古老陆核花岗-绿岩地体中的韧性剪切带是最重要的控矿构造.文章列举夹皮沟韧性剪切带、小四平-南岔韧性剪切带、山门-叶赫韧性剪切带等实例对吉林省东部韧性剪切带的展布规律、基本特征及其控矿作用进行了详细论述,总结了韧性剪切带与金、银矿产的关系.     

江西彭山锡(铅锌)多金属矿田构造地质特征及成矿机理探讨

江西彭山锡 (铅锌 )多金属矿田位于长江中下游多金属成矿带中的九瑞地区。彭山隐伏钙碱性花岗岩体侵位为锡 (铅锌 )多金属矿的形成提供了热动力及成矿物质来源。自晋宁期形成的长期活动的基底深断裂和由彭山岩体底辟侵位形成的穹窿构造 ,以及由此派生的次级断裂带 ,诸如环形滑脱断裂、顶脱断裂和节理裂隙 ,都为含矿热液的运移和矿体就位提供了空间。形成彭山岩体 (DI >90 )的岩浆经历了较为充分的分异 ,在岩浆热液对流系统和地下水对流系统的双重作用下 ,含矿热液流体的成分随温度降低而改变 ,导致 6个阶段的成矿作用。各阶段的矿物组合随温度而变化 ,在空间上有一定的叠加 ,在萤石 -硅酸锡阶段 ,还发现了马来亚石。各类矿产在空间上的分布呈环状 ,即由岩体中心向外围依次出现内侧的高温As-Sn带、中间的Sn -Pb和Pb -Zn -Ag带和外围的低温萤石带。文中还以锡为例 ,详细讨论了锡在黑云母与热液流体之间的迁移及其矿化过程。     

双层界面重磁联合反演方法研究

Based on the synchronous joint gravity and magnetic inversion of single interface by Pilkington and the need of revealing Cenozoic and crystalline basement thickness in the new round of oil-gas exploration, we propose a joint gravity and magnetic inversion methodfor two-layer models by concentrating on the relationship between the change of thicknessI and position of the middle layer and anomaly and discuss the effects of the key parameters. Model tests and application to field data show the validity of this method.     

建(构)筑物控制爆破拆除的仿真模拟

介绍了在ABAQUS有限元框架内,建（构）筑物爆破拆除仿真模拟的基本方法。提出了爆破缺口高度的确定方法、结构坍塌的力学判据与结构的离散化方法,利用ABAQUS有限元软件的非线性瞬态显式动力学模块模拟结构的失稳及倒塌过程,并用该方法对一个拆除爆破实例进行了仿真模拟。模拟结果表明,结构的坍塌过程及爆堆形状与实际接近。     

Drying and dying of a subducted slab: Coupled Li and B isotope variations in Western Anatolia Cenozoic Volcanism

In lavas spanning ~ 10Ma of subduction-related volcanism in Western Anatolia, we observe remarkably similar patterns of δ⁷Li and δ¹¹B variation. In this setting, magmatism records a transition from calc–alkaline to ultrapotassic character, consistent with overall lower mean extents of melting, and a changing mantle source that reflects a fractionating, higher temperature slab input consistent with the gradual cessation of subduction. Subsequent rift-related intraplate magmatism record δ⁷Li signatures within the range observed for MORBs and OIBs, indicating an abrupt transition to a mantle source unmodified by subduction.     

Meteoritic and bedrock constraints on the glacial history of Frontier Mountain in northern Victoria Land, Antarctica

In 2001, a small H4 chondrite, Frontier Mountain (FRO) 01149, was found on a glacially eroded surface near the top of Frontier Mountain, Antarctica, about 600 m above the present ice level. The metal and sulphides are almost completely oxidized due to terrestrial weathering. We used a chemical leaching procedure to remove weathering products, which contained atmospheric ¹⁰Be and ³⁶Cl in a ratio similar to that found in Antarctic ice. The FRO 01149 meteorite has a terrestrial age of 3.0 ± 0.3 Myr based on the concentrations of the cosmogenic radionuclides ¹⁰Be, ²⁶Al and ³⁶Cl. This age implies that FRO 01149 is the oldest stony meteorite (fossil meteorites excluded) discovered on Earth. The noble gas cosmic ray exposure age of FRO 01149 is ~ 30 Myr. The meteorite thus belongs to the 33 Myr exposure age peak of H-chondrites.The bedrock surface on which FRO 01149 was found has wet-based glacial erosional features recording a former high-stand of the East Antarctic ice sheet. This ice sheet evidently overrode the highest peaks (> 2800 m a.s.l.) of the inland sector of the Transantarctic Mountains in northern Victoria Land. We argue that FRO 01149 was a local fall and that its survival on a glacially eroded bedrock surface constrains the age of the last overriding event to be older than ~ 3 Myr. The concentrations of in-situ produced cosmogenic ¹⁰Be, ²⁶Al and ²¹Ne in a glacially eroded bedrock sample taken from near the summit of Frontier Mountain yield a surface exposure age of 4.4 Myr and indicate that the bedrock was covered by several meters of snow. The exposure age is also consistent with bedrock exposure ages of other summit plateaus in northern Victoria Land.