九寨沟M_S7.0地震对巴颜喀拉块体东北缘活动断裂影响的有限元模拟

在详细调研地震地质资料的基础上,构建了巴颜喀拉地块东北缘三维有限元模型。以九寨沟M_S7.0地震同震位错为荷载,模拟计算了九寨沟地震的发生对巴颜喀拉块体东北缘主要活动断裂加卸载效应的影响。模拟结果显示,九寨沟地震的发生对龙日坝断裂、虎牙断裂、青川-平武断裂西段、迭部-白龙江断裂西段和东段、临潭-宕昌断裂东段,以及处于甘青川交界危险区内的东昆仑断裂东段、塔藏断裂西段,处于六盘山南-西秦岭东危险区的西秦岭北缘断裂东段表现为库仑应力加载;对岷江断裂、塔藏断裂东段库仑应力卸载效应显著。     

巴颜喀拉块体东北缘GPS应变率空间分布特征及其与2017年九寨沟MS7.0地震的关系

巴颜喀拉块体东北缘是构造变形和地震活动较强的区域, 2017年九寨沟M_S7.0地震就发生在该区域内。 利用多尺度球面小波方法解算GPS应变率场, 分析巴颜喀拉块体东北缘2009年至2017年的应变率场分布特征, 该方法的优点是可以将GPS应变率场按照不同的空间尺度进行小波分解, 给出不同空间尺度的应变率场。 结果表明在2017年九寨沟地震之前, 震中附近应变积累显著, 虎牙断裂北延断裂的左旋走滑速率为3.0 mm/a, 拉张速率为3.1 mm/a, 表明该条断裂以左旋走滑为主兼有拉张特征, 与九寨沟地震的震源机制解一致。 除九寨沟震中附近外, 在岷县与漳县交界处、 理县和汶川、 青川等地区主应变率、 面应变率、 最大剪应变率也较大, 这可能与2013岷县漳县(M_S6.6)、 2008年汶川(M_S8.0)、 2014年理县(M_S4.8)以及2014青川县(M_S4.8)地震有关。     

Middle Permian palaeobiogeography study in East Kunlun,A’nyêmaqên and Bayan Har

Three regions can easily be identified in the study area according to the Middle Permian palaeobiogeographic distribution of biota, they are the southern slope of East Kunlun, A'nyêmaqên and Bayan Har. Biotic constitution and ecology in the southern slope of East Kunlun and Bayan Har are very similar. Both the diversity and abundance of organisms in these two areas are very high and reefs are widely developed. However, biotic diversity and abundance in A'nyêmaqên which is between the above two areas are obviously low. Differentiation of palaeobiogeographic distribution in these areas should be due to the baring of A'nyêmaqên ocean in the time of Middle Permian. Middle Permian radiolarian chert and thick abyssal red ooze are widely spread in A'nyêmaqên, implying that the A'nyêmaqên ocean had a great scale in size. Vast scale of deep ocean basin became an impassable gulf for some of the benthos, and as a result, only part of the organisms could have the chance to get to the isolated islands situated in ocean basin. Small living space and hard conditions in the islands further limited the abundance and diversity of biota. Tectonic background reflected by the geochemical study of basalt in the three areas is coupling well enough with the palaeobiogeographic division.     

Juvenile specimens of Pinacosaurus grangeri Gilmore, 1933 (Ornithischia: Ankylosauria) from the Late Cretaceous of China, with comments on the specific taxonomy of Pinacosaurus

Four juvenile specimens referable to Pinacosaurus grangeri (Ankylosauria: Dinosauria) are described from the Campanian (Upper Cretaceous) locality Bayan Mandahu in northern Inner Mongolia Autonomous Region (People’s Republic of China). All the specimens preserve the skulls as well as, in some cases, mandibles, postcrania, and osteoderm. They are not taphonomically deformed by expanding matrix distortion, unlike many Gobi specimens, including the holotype of P. grangeri. Bayan Mandahu is also the type locality for Pinacosaurus mephistocephalus. The proximity in space and time of these two closely related species warrants a generic and specific revision for Pinacosaurus. The distinction of the two species is based on characters of the squamosal dermal elaborations, cranial roof posterior to the orbits, premaxillary notch, and distal margin of the ilium. Although a relatively well-represented ankylosaur taxon, the phylogenetic position of Pinacosaurus has not been unequivocally resolved. A new analysis recovers Pinacosaurus as the most basal member of the Ankylosaurinae.     

Tectonostratigraphic evolution of the Morichito piggyback basin, Eastern Venezuelan Basin

The Morichito piggyback basin (MPB) is a SW-NE-oriented depocenter in the Eastern Venezuelan Foreland Basin (EVFB). This piggyback basin formed by overlying the Pirital thrust during the middle to late Miocene as a result of oblique collision between the Caribbean and South-American Plates. The MPB covers an area encompassing approximately 1000 km² between the Serrania del Interior range and the Pirital high, which is a hanging wall uplift along the Pirital thrust that acts as a confining barrier on the southern boundary of the MPB. Previous studies have tried to address the tectonostratigraphic significance of the MPB, but new biostratigraphic information and recently acquired 3D seismic data have allowed us to expand the understanding of this basin. The MPB occupies a relatively small area of the EVFB; however, the MPB contains a valuable stratigraphic record that can be used to unveil the timing of the main deformational events that took place in the EVFB.This work presents the tectonostratigraphic evolution of the MPB by defining four tectonostratigraphic sequences (T1-T4). Each sequence was defined on the basis of integration of well logs, biostratigraphy, and seismic geomorphological interpretations. T1 (24-16 Ma) (late Oligocene to middle Miocene), which was deposited in shallow-marine environments, extends to the south of the Pirital high beyond the boundaries of the MPB. T1 is equivalent to the early foredeep stage of the EVFB, having been formed when structural deformation and uplifting were already occurring to the north on the proto-Serrania del Interior range (∼24-16 Ma) and the Pirital thrust was active (∼22 Ma). T2 (16-11 Ma) (middle to late Miocene) is composed of alluvial-fan deposits derived from the proto-Serrania del Interior range. The geometry and internal configuration of T2 indicate that during this time the basin was transitioning from an open-foreland basin to a confined piggyback basin. During deposition of T2, the Pirital fault was active as an out-of-sequence thrusting event (16-∼11 ma). T3 (late Miocene) and T4 (early Pliocene to Recent), composed of shallow-marine and fluvial deposits, were deposited in an already restricted piggyback basin. The Pirital high was already in place during deposition of T3 (∼11-9.3 ma). T3 and T4 represent the final phases of MPB infilling, when tectonic activity and subsidence were at their lowest rates. MPB sedimentary infilling dates the activity of thrusting events in the proto-Serrania del Interior (∼24-16 Ma), timing of maximum deformation associated with the Pirital out-of-sequence thrusting event (16-∼11 Ma), timing of final emplacement of the Pirital high (∼11-9.3 Ma), and the beginning of tectonic quiescence (<5.2 Ma).     

Formation Conditions and Sedimentary Model of Over-Flooding Lake Deltas within Continental Lake Basins: An Example from the Paleogene in the Jiyang Subbasin, Bohai Bay Basin

A large quantity of drilling core, paleontology, geochemistry and geophysics data revealed several features of the Jiyang subbasin during the deposition of the Ek1-Es4 x members:(1) the paleotopography of the gentle slope belt had an extremely low gradient;(2) the paleoclimate frequently alternated between dry and wet periods in a generally arid setting;(3) there was strong weathering around the periphery of the basin;(4) the lake was very shallow;(5) the lake level frequently rose and fell; and(6) the sedimentary environment of the gentle slope belt was an overflooding lake. All of these factors provided favorable geological conditions for the development of an over-flooding lake delta. The lithologies of the continental over-flooding lake delta deposits are complex and diverse. The compositional maturity is moderate to low, and the grain size distribution curves and sedimentary structures indicate the presence of both gravity and traction currents. The sedimentary microfacies associations consist of a combination of ordered superposition of flood channels, distributary channels and sheet sands. The delta exhibits a weak foreset seismic reflection. The over-flooding lake delta deposits are laterally extensive. The sandstone content is high, and the individual sandstone beds are thin. The flood channel and distributary channel deposits exhibit evidence of bifurcation and lateral migration. The distribution of the sandbodies and the oxidation color of the mudstones provide evidence of cyclic deposition. The paleoclimate was the dominant factor controlling the development of the over-flooding lake delta. Due to the frequently alternating wet and dry paleoclimates, the over-flooding lake delta is characterized by the development of a broad upper plain and a lower delta plain. The upper delta plain is characterized by flood channel deposits, whereas the lower delta plain is represented by distributary channel deposits. The transition zone is characterized by the interaction of flood channels and distributary channels. Due to fault activity, the sandbodies of the over-flooding lake delta were juxtaposed against hydrocarbon source rocks, which was favorable for the development of lithologic reservoirs or structural-lithologic reservoirs. The lower delta plain deposits comprise the most favorable reservoirs.     

巴颜喀拉-川西边缘前陆盆地演化

巴颜喀拉古特提斯洋的消亡过程反映在巴颜喀拉残留盆地到边缘前陆盆地转化的沉积记录中。鉴于这个前陆盆地与其向克拉通延伸的组成部分——四川盆地现为龙门山逆冲带所分隔,以致已往的沉积盆地研究多将其相割裂,本文将结合巴颜喀拉洋的消亡过程,把这两个盆地视为一个统一整体来加以分析,研究其演变历程。
晚二叠世,扬子板块向西楔入的同时,发生向北（昆仑-柴达木陆块）和向南（羌塘-昌都陆块）的双向俯冲消减。本文提出了巴颜喀拉洋的主体闭合,从而开始转化为边缘前陆盆地阶段的时间是在拉丁（T₂²）中晚期,而不是晚三叠世的见解。这点可由拉丁中晚期时,四川盆地川中广大地区形成与前陆挠曲沉降相对应的前陆隆起得以证明。此时期发生的前陆沉降,结束了被动边缘的饥饿（T₁—T₂¹）沉积盆地状态,充填了厚逾2,000—10,000m的类复理石沉积,并向扬子克拉通边缘超覆。随着逆冲带的由北向南推进,在诺利一瑞替期形成了滨海含煤磨拉石和陆相含煤磨拉石（逆冲褶皱带地区大多后期被剥蚀）。晚三叠世中晚期,逆冲带侵位推进到四川盆地西部边缘的龙门山地带,从而前陆盆地迁移入四川盆地内,进入陆内汇聚的后造山陆相磨拉石前陆盆地阶段。晚白垩世一早第三纪,因四川盆地晚期的抬升,这一前陆盆地便逐渐萎缩消亡。     

白云鄂博铁、铌、稀土矿床:研究进展、存在问题和新认识

白云鄂博是世界第一大稀土元素矿床,其稀土元素资源量占世界目前已知稀土元素资源总量的三分之二以上,具有重要的经济和战略地位。白云鄂博自1927年发现至今已有92年,对其的开发和研究历史悠久,在赋矿碳酸岩的成因、成矿年代、稀土矿物学等方面取得了一系列重要进展,为碳酸岩型稀土元素成矿理论发展做出了突出贡献。由于矿床经历了成矿后复杂的构造变形和热液蚀变,致使其地质、地球化学特征复杂,学界对其成因和成矿过程一直存在不同认识,对成矿碳酸岩的岩浆演化、稀土元素迁移与富集机理等方面的研究也相对薄弱。笔者最新研究表明,矿区过去被认为是下白云鄂博群的H1、H2、H9岩石单元并非沉积变质岩或变质火山岩,而应为岩浆侵入成因,矿区其他岩石单元(H3～H7)的成因也值得商榷。H9岩石单元中的黑云母岩(前人称为黑云母板岩)和富含黑云母的碳酸岩(前人称为暗色板岩)为成矿碳酸岩的一部分,是碳酸岩不同岩相带的表现。黑云母岩和富黑云母碳酸岩相对于含矿碳酸岩具有相对低的稀土元素含量和轻、重稀土元素比值,表明岩浆演化可能对稀土元素的富集和分异具有重要贡献。矿区主要岩石单元成因的新认识不仅为矿床成因、成矿背景研究提供了新的依据,同时也为研究区域构造演化、正确厘定矿区构造式样和指导矿区深部和外围找矿提供了新的思路。     

内蒙古巴彦宝力格煤田赛汉塔拉组中煤层煤质特征分析

论述了内蒙古巴彦宝力格煤田赛汉塔拉组中煤层煤质特征及用途。本区煤属中灰、低硫、低磷、特低氯、低～中热值,各煤层煤类以长焰煤为主,有少量褐煤。煤中有害成分低,发热量较高,是良好的民用及动力用煤。用于火力发电,各种工业锅炉使用,也可在建材工业,化学工业中做焙烧材料。