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131.
对多震相走时层析成像方法进行改进和优化, 使用朝鲜半岛陆地和近海的地震记录, 对朝鲜半岛南部(34.5°N~39°N,125°E~130°E)进行地震波走时反演, 获得了本研究区的三维速度结构成像结果.分析了沉积层、基底、上地壳、康腊面、下地壳和莫霍面的特征.研究了不同地质区的深部结构的主要差别、主要断裂特征、 海陆交界的地壳特征等.可以发现京畿山地与沃川褶皱带、太白山褶皱带、临津江褶皱带深部结构的差异尤为明显. 相似文献
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In the Korean Peninsula the Meso-Cenozoic basins were mainly formed due to fault block and block movement. The Mesozoic fracture structures correspond basically to modern large rivers in direction. Such faults were usually developed to rift and formed lake-type tectonic basin, such as the Amrokgang-, Taedonggang-, Ryesonggang-, Hochongang-, Jangphari-, Susongchon-, Pujon-, and Nampho basins. The Mesozoic strata are considered to be divided into the Lower Jurassic Taedong System, Upper Jurassic Jasong System, Upper Jurassic-early Lower Cretaceous Taebo System, and the Upper Cretaceous-Paleocene (Chonjaebong, Hongwon, Jaedok Series) . The Cenozoic block movement succeeded the Mesozoic fault block movement. The Kilju-Myonchon Graben and Tumangang Basin, etc, are the basins related to the fault zones developed from the Oligocene to Miocene. In addition, the Tertiary basins were formed in many areas in the Miocene ( e. g. Sinhung, Oro, Hamhung, Yonghung, Anbyon, Cholwon, etc) . The Cenozoic sedimentation occurred mainly from the late Oligocene to Miocene. The Kilju-Myongchon Graben was the fore deep connected to the sea and the basins inclined in the Chugaryong Fault Zone are intramountain basins. Therefore, coal-bearing beds and clastic rocks in the intramountain basins and rare marine strata and terrigenous clastic rocks are main sedimentary sequences in the Cenozoic. 相似文献
135.
用五点法进行抽样调查并探讨了湿地松粉蚧(Oracella acuta Lobdell)侵入后,湿地松(Pinuselliotii)新植树皮化学成分与粉蚧为害的关系。结果表明:均衡、协调的营养对粉蚧生长和繁殖有利;粉蚧为害主要导致新梢树皮蛋白质、粗灰分含量明显增加,还原糖含量明显减少;粉蚧发生高峰期,新梢树皮蛋白质含量与与粉蚧虫口密度呈显著正相关。 相似文献
136.
Thermal histories of Cretaceous sedimentary basins in the Korean peninsula have been assessed to understand the response of the East Asian continental margin to subduction of the Paleo‐Pacific (Izanagi) Plate. The Izanagi Plate subducted obliquely beneath the East Asian continent during the Early Cretaceous and orthogonally in the Late Cretaceous. First, the Jinan Basin, a pull‐apart basin, was studied by illite crystallinity and apatite fission‐track analyses. Analytical results indicate that Jinan Basin sediment was heated to a maximum temperature of approximately 287°C by burial. The sediment experienced two cooling episodes during ca 95–80 Ma and after ca 30 Ma, with a quiescent period between them. A similar cooling pattern is recognized in the Gyeongsang Basin, the largest Cretaceous basin in Korea. The Jinan and Gyeongsang Basins were cooled mainly by exhumation between ca 95 and 80 Ma, but the former was exhumed slightly earlier than the latter by transpressional force due to the subduction direction change of the Izanagi Plate. Comparison of thermal history of Korean Cretaceous basins with those of granitoids in northeastern China and the accretionary complexes in southwestern Japan reveals that the Upper Cretaceous regional exhumation of the East Asian continental margin including the Korean peninsula during ca 95–80 Ma was facilitated by the subduction of the Izanagi–Pacific ridge, which migrated northeastwards with time, resulting in the end of regional exhumation at ca 80 Ma in this region. 相似文献
137.
采用热释光和红外光释光测年技术获取了采自朝鲜半岛西南部和顺支石墓遗址剖面中的陶片和沉积物的年龄.古陶片的热释光年龄分别是(3100±210)a和(3680±320)a,相应文化层中支石墓墓葬层位的红外光释光年龄分别是(2200±190)a和(2900±310)a.古陶片的热释光年龄老于地层的红外光释光年龄,代表着支石墓... 相似文献
138.
Sand and silt grains: Predetermination of their formation and properties by microfractures in quartz
Examination of quartz from plutonic source rocks, sediments and soils, using both optical and scanning electron microscopes, reveals that the mineral is, almost always, cut by sets of partially healed, subplanar, subparallel microfractures dividing it into sheets typically one to a few micrometres thick. The structure, which originates in source rocks, is not due to crystal cleavage although it does show weak crystallo‐graphic influence in its directions. One to several sets of microfractures, intersecting at varying angles, can be present in any one quartz crystal. The microfractures vary in quality like cleavages; separation takes place readily along some, less so along others. In superficial environments, the ease with which microfractures can be reopened largely controls the durability of quartz and the degree to which comminution can proceed. However, this type of breakage must cease when grains are one sheet thick (about 2–20 Mm in diameter). Hence quartz suddenly changes from being the dominant mineral in silt fractions to a normally minor constituent of clay fractions. The shape of grains depends largely on the number of (and angles between) microfrac‐ture sets present in the parent quartz. Most quartz grain surfaces represent fractures whose details characterize the pre‐emergent history of the quartz rather than sedimentary environments. 相似文献
139.
朝鲜半岛中南部三叠纪岩浆岩的分布、系列与成因浅析 总被引:1,自引:1,他引:0
朝鲜半岛发育大量三叠纪侵入体,主要分布在半岛中部一个北东向走廊地带,该带状区域根据岩性差异,以洪城-高城一线为界分为两个亚带:北亚带(正长岩带/碱性岩带)主要分布在狼林地块南部及京畿地块北部,为碱性系列,以正长岩类为主;南亚带(二长岩带)主要分布在京畿地块南部-岭南地块,多为亚碱性系列,以(纹长)二长岩类为主,部分岩体有闪长岩-辉长岩端元,南部有少量A型花岗岩。这些岩体多形成于ca.230~220Ma,如本文获得的北亚带江北黑云母正长岩228.7±0.8 Ma锆石U-Pb谐和年龄。它们与本区高级变质作用时代接近,分布范围大致对应但稍大,说明它们是同成因的。岩石化学方面,这些岩体均显示高场强元素亏损,轻稀土和大离子亲石元素富集的典型的大陆岩石圈特征。南北亚带相比,北亚带岩体SiO_2和Na_2O等的含量整体上略低,而K_2O、Sr、Ba、La、Eu、Y、Cr等及稀土元素含量略高,轻重稀土分异程度((La/Yb)N)略高。空间上,两个亚带内K_2O/Na_2O和SiO_2有相反的变化趋势:从南向北,两个亚带内K_2O/Na_2O逐渐升高,SiO_2含量逐渐降低;但K_2O+Na_2O和Sr/Y的变化是相似的:南亚带从南向北,北亚带从北向南,两者逐渐降低。我们认为这些岩浆岩为同碰撞或者碰撞后产物,两个亚带之间的界线接近华北和华南古陆缝合带,岩性和成分的空间差异受控于华南古陆(朝鲜半岛南部)向华北古陆(朝鲜半岛北部)之下俯冲所形成的特定壳幔结构。 相似文献
140.