Crustal Structure of Collisional Orogens: The Ural Mountains, Russia

小行星9219915 俄罗斯中部的乌拉尔山脉形成了一条3 000公里长的古生代线性造山带，是研究碰撞造山作用和大陆地壳演化的一系列基本问题的独特的天然实验室。 乌拉尔山脉与其他古生代造山带如阿巴拉契亚山脉、加里东山脉和瓦里斯喀德斯山脉有几个明显的区别。 其中主要有：（1）明显存在（2）根据现有资料，乌拉尔山明显缺乏同碰撞或碰撞后的崩塌，（3）乌拉尔山暴露的地壳水平相对较浅，变质程度一般较低，（4）乌拉尔造山带地壳反射率的性质和分布。 特别是，乌拉尔山脉和阿巴拉契亚山脉之间的早期造山演化的明显相似性，以及随后的后造山路径的分歧，提供了一个特殊的机会，以评估各种造山过程中的作用，下地壳结构的发展。 例如，如果在阿巴拉契亚山脉内部下方观察到的明显的下地壳分层与造山后伸展有关，那么乌拉尔山脉下方是否会不存在这种分层？ 乌拉尔山脉在造山发展过程中是否保留了一个中间阶段，介于阿巴拉契亚山脉等较成熟的崩塌造山带和阿尔卑斯山、喜马拉雅山等较近代的挤压带之间？ 主要研究人员将与俄罗斯科学家在俄罗斯Scheelite（叶卡捷琳堡附近，前斯维尔德洛夫斯克）的Bazhenov地球物理考察队开展合作研究计划，根据其广泛的现有地球物理数据库对乌拉尔地壳结构的性质和起源进行全面研究。 这次合作是一个更大的长期计划的初始阶段，该计划将乌拉尔山脉与其他古生代造山带进行比较和对比，最终导致第一个横跨乌拉尔山脉的深地震反射剖面。 这一努力也是美国科学家与欧洲岩石圈研究中心（EUROPROBE）的首次合作，后者是一个协调欧洲岩石圈研究的重要新倡议。 美国部分将侧重于乌拉尔和阿巴拉契亚构造的比较，补充EUROPROBE对乌拉尔与华力西演化的调查。 特别是，他们将侧重于俄罗斯反射（主要是浅层），折射和DSS（深层地震探测）数据的再处理和合成，目的是绘制地壳结构并了解乌拉尔和附近地区的中生代历史。 在此过程中，他们将与俄罗斯合作者建立对各种现有数据集及其解释的共同知识。 值得注意的是，巴热诺夫探险队是乌拉尔所有地球物理数据的中心（包括DSS和反射数据，重力和磁力数据，热流等）。这些数据中的大多数，在与该研究所的科学家发表联合声明的条件下，可以不受限制地获得。 ***

9219915 Brown The Ural Mountains of central Russia form a 3,000-km linear orogenic belt of Paleozoic age and constitute a unique natural laboratory to address a number of basic issues concerning collisional orogenesis and the evolution of continental crust. Several features appear to distinguish the Urals from other Paleozoic orogenic belts such as the Appalachians, Caledonides, and Variscides. Primary among these are (1) the apparent presence (based on seismic velocities) of a preserved crustal root below the Urals, (2) the apparent lack of syn- or post-collisional collapse evidenced in the Urals based on existing data, (3) the relatively shallow crustal level and generally low metamorphic grade exposed in the Urals, and (4) the nature and distribution of crustal reflectivity in the Ural orogen. In particular, the apparent similarity in early orogenic evolution between the Urals and the Appalachians, and the subsequent divergence in post-orogenic paths, offer a special opportunity to evaluate the role of various orogenic processes in the development of lower crustal structure. For example, if the prominent lower crustal layering observed beneath the Appalachian interior relates to post-orogenic extension, will it be absent beneath the Urals? Do the Urals preserve an intermediate stage in orogenic development between the more mature collapsed orogens like the Appalachians and more recent compressional belts like the Alps and Himalayas? The Principal Investigators will initiate a collaborative research program with Russian scientists at the Bazhenov Geophysical Expedition in Scheelite (near Ekaterinburg, formerly Sverdlovsk), Russia, for a comprehensive study of the nature and origin of the crustal structure of the Urals based on their extensive existing geophysical database. This collaboration constitutes the initial phase of a larger, long-term program to compare and contrast the Urals with other Paleozoic orogens, eventually leading to the first deep seismic reflection profile across the Urals. This effort also represents the first collaboration between US scientists and EUROPROBE, a major new European initiative to coordinate lithospheric studies in Europe. The US component will focus on a comparison of Uralian and Appalachian structure, complementing EUROPROBE's investigation of the Urals versus Variscan evolution. In particular they will focus on reprocessing and synthesis of Russia reflection (mostly shallow), refraction and DSS (deep seismic sounding) data, with the aim of mapping the crustal structure and understanding the Phanerozoic history of the Urals and nearby regions. In doing this, they will be establishing with their Russian collaborators a common knowledge of the various existing datasets and their interpretations. It is important to note that the Bazhenov Expedition is the center for all geophysical data available on the Urals (including DSS and reflection data, gravity and magnetic data, heat flow, etc.) and the majority of these data, are of unrestricted access under the conditions of a joint statement with scientists from that institute. ***