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11.
12.
山东海阳所麻粒岩向过渡榴辉岩转化的变质动力学过程及其构造意义 总被引:8,自引:3,他引:5
在山东半岛东南端的乳山海阳所,角闪岩和长英质片麻岩呈互层产出.在某些角闪岩层的中心残留有弱变形的麻粒岩和强变形的过渡榴辉岩(斜长石榴辉岩)团块.在弱变形的麻粒岩团块中发育有窄的(<1cm)剪切条带.沿着这些剪切条带和在强变形过渡榴辉岩团块中,原麻粒岩被转化为含斜长石的过渡榴辉岩.变形和流体在这一转化过程中加速了元素扩散和迁移的速度,在变形强和有流体加入的部位麻粒岩向榴辉岩转化的程度明显增强.麻粒岩相矿物组合(Cpx-Ⅰ+Opx+Pl-Ⅰ+ Hbl-Ⅰ + Grt-Ⅰ+ Ilm)及其花岗变晶结构被完好地保存于弱变形的麻粒岩中,其矿物成分显示出0.8~0.9 GPa和780℃~830℃的麻粒岩相变质条件.榴辉岩相叠加在麻粒岩中形成了一系列的环边状矿物和结构:环边状石榴石(Grt-Ⅱ)形成于麻粒岩相斜长石(Pl-Ⅰ)和暗色矿物(如Cpx-Ⅰ、Opx和Hbl-Ⅰ)的交界处,细粒石榴石(Grt-Ⅱ)、富钠单斜辉石(Cpx-Ⅱ)和石英形成于麻粒岩相角闪石(Hbl-Ⅰ)的外缘.同时榴辉岩相叠加造成麻粒岩相单斜辉石边缘钙契尔马克组份的降低和硬玉组份的升高.但在弱变形的麻粒岩中,麻粒岩相单斜辉石(Cpx-Ⅰ)的外缘并无榴辉岩相单斜辉石形成.沿着弱变形麻粒岩中的剪切条带和在过渡榴辉岩中,榴辉岩相矿物[Grt-Ⅱ+ Omp/Di(Cpx-Ⅱ)+ Ab(Pl-Ⅱ)+ Qtz + Hbl-Ⅱ+ Ky + Zo + Rut]广泛发育,它们的定向排列形成了明显的面理.其形成的温压条件为1.0~1.4 GPa和560℃~680℃,为过渡榴辉岩相变质.虽然其中仍然残留有被拉长的麻粒岩相单斜辉石,但它们含有很高的硬玉组份,且其外缘环绕有细粒的钠质透辉石或绿辉石(Cpx-Ⅱ).海阳所榴辉岩相变质的温压条件远远低于位于海阳所东南和东北的苏鲁超高压变质带中柯石英榴辉岩变质的温压条件.因此海阳所地区代表一条不同于超高压变质带的冷榴辉岩带,它可能与大别山南部的冷榴辉岩带相当.苏鲁超高压变质带的南部边界位于海阳所以北. 相似文献
13.
石场-中楼盆地位于郯庐断裂带中段的沂河-沭河地区。郯庐断裂左旋切割了秦岭-大别-胶南造山带及前中生代地层,研究区内沂河-沭河断裂切割了年龄为136.2Ma(40Ar/39Ar法)的胶南造山带北缘剪切带,并被时代为119Ma(K-Ar法)的青山群地层不整合覆盖,显示郯庐断裂在早白垩世曾发生了明显的走滑运动。石场-中楼盆地受沂河-沭河断裂的控制,整体为长60km、宽30km,长宽比近于2∶1的“菱型”构造盆地。盆地内早白垩世莱阳群的沉积厚度大于6263.71m,沉积速率大于0.4mm/a;沉积相特征反映盆地具有深而窄,沉积速度快、沉积相变剧烈的特点。盆地沉积中心的迁移方向与边界断裂的左旋走滑效应一致,“边走滑边沉积”的特征明显。根据构造背景、构造格架及沉积特征,确定石场-中楼盆地为郯庐断裂早白垩世左旋走滑过程中形成的拉分盆地 相似文献
14.
Hiromi Watanabe Eriko Seo Yoshimi Takahashi Takao Yoshida Shigeaki Kojima Katsunori Fujikura Hiroshi Miyake 《Journal of Oceanography》2013,69(1):129-134
Vesicomyid bivalves have a substantial biomass in deep-sea chemosynthetic biological communities in the Pacific. Using a novel multiplex-PCR (mPCR) method to identify the co-occurring vesicomyids in Sagami Bay, we analyzed the distribution of Calyptogena okutanii and Calyptogena soyoae along environmental gradients. All the known distributions of C. okutanii indicated the different preferences in salinity and temperature to those of C. soyoae, and in Sagami Bay, depth seemed to be an important environmental factor, too. Although the concentration of hydrogen sulfide in sediment was not examined, our results showed that the distributions of these two Calyptogena clams were affected by salinity and temperature. 相似文献
15.
Satoshi Noguchi Naoyuki Shimoda Osamu Takano Nobutaka Oikawa Takao Inamori Tatsuo Saeki Tetsuya Fujii 《Marine and Petroleum Geology》2011,28(10):1817-1828
The reservoir architecture of methane hydrate (MH) bearing turbidite channels in the eastern Nankai Trough, offshore Japan is evaluated using a combination of 3-D seismic and well data. On the 3-D seismic section, the MH-bearing turbidite channels correspond to complex patterns of strong seismic reflectors, which show the 3-D internal architecture of the channel complex. A seismic-sequence stratigraphic analysis reveals that the channel complex can be roughly classified into three different stages of depositional sequence (upper, middle, and lower). Each depositional sequence results in a different depositional system that primarily controls the reservoir architecture of the turbidite channels. To construct a 3-D facies model, the stacking patterns of the turbidite channels are interpreted, and the reservoir heterogeneities of MH-bearing sediments are discussed. The identified channels at the upper sequence around the β1 well exhibit low-sinuosity channels consisting of various channel widths that range from tens to several hundreds of meters. Paleo-current flow directions of the turbidite channels are typically oriented along the north-northeast-to-south-southwest direction. High-amplitude patterns were identified above the channels along the north-to-south and north-northeast-to-south-southeast directions. These roughly coincide with the paleo-current flow of the turbidite channels. An interval velocity using high-density velocity analysis shows that velocity anomalies (>2000 m/s) are found on the northeastern side of the turbidite channels. The depositional stage of the northeastern side of the turbidite channels exhibits slightly older sediment stages than the depositional stages of the remaining channels. Hence, the velocity anomalies of the northeastern side of the channels are related to the different stages of sediment supply, and this may lead to the different reservoir architectures of the turbidite channels. 相似文献
16.
Tomotaka Iwata Takao Kagawa Anatoly Petukhin Yoshihiro Ohnishi 《Journal of Seismology》2008,12(2):223-234
We constructed a prototype of the basin and crustal structure model for the Kinki area, southwest of Japan, for the simulation
of strong ground motions of hypothetical crustal and subduction earthquakes. We collected results of the deep seismic velocity
profiles obtained by the reflection experiments and seismic imaging results, which were conducted in the Kinki area. The obtained
profiles give underground velocity structures of the crust, from the surface to the subducting slab. We also gather the basin
velocity structure information of the Osaka, Kyoto, Nara, and Ohmi basins. To examine the applicability of the constructed
velocity structure model to the ground motion simulation, we simulated waveforms of an intermediate size event occurred near
the source area of the hypothetical subduction earthquakes. Simulated ground motions using the basin and crustal velocity
structure model are fairly well reproducing the observations at most of stations, and the constructed basin and crustal velocity
structure model is applicable for the long-period ground motion simulations. 相似文献
17.
Haruko Sekiguchi Masayuki Yoshimi Haruo Horikawa Kunikazu Yoshida Sunao Kunimatsu Kenji Satake 《Journal of Seismology》2008,12(2):185-195
We studied the long-period ground motions in the Osaka sedimentary basin, Japan, which contains a 1- to 3-km thickness of
sediments and is the site of many buildings or construction structures with long-natural period. We simulated the broadband
ground motions likely to be produced by the hypothetical Nankai earthquake: the earthquake expected to give rise to the most
severe long-period ground motion within the basin. For the simulation, we constructed multiscale heterogeneous source models
based on the Central Disaster Management Council of Japan (CDMC) source model and adopted a hybrid computation method in which
long-period motion and short-period motion are computed using a 3-D finite difference method and the stochastic Green’s function
method, respectively. In computing long-period motions, we used a 3-D structure model of the crust and the Osaka sedimentary
basin. The ground motions are estimated to have peak velocities of 50–90 cm/s, prolonged durations exceeding 300 s, and long
predominant periods of 5–10 s in the area with great thickness of sediments. The predominant periods are in agreement with
an approximate evaluation by 4 H/V
s where H and V
s are the thickness of the sediment and the average S wave velocity, respectively. 相似文献
18.
Molecular and isotopic characteristics of gas hydrate-bound hydrocarbons in southern and central Lake Baikal 总被引:4,自引:4,他引:0
Akihiro Hachikubo Oleg Khlystov Alexey Krylov Hirotoshi Sakagami Hirotsugu Minami Yutaka Nunokawa Satoshi Yamashita Nobuo Takahashi Hitoshi Shoji Shin’ya Nishio Masato Kida Takao Ebinuma Gennadiy Kalmychkov Jeffrey Poort 《Geo-Marine Letters》2010,30(3-4):321-329
We investigated the molecular composition (methane, ethane, and propane) and stable isotope composition (methane and ethane) of hydrate-bound gas in sediments of Lake Baikal. Hydrate-bearing sediment cores were retrieved from eight gas seep sites, located in the southern and central Baikal basins. Empirical classification of the methane stable isotopes (δ13C and δD) for all the seep sites indicated the dominant microbial origin of methane via methyl-type fermentation; however, a mixture of thermogenic and microbial gases resulted in relatively high methane δ13C signatures at two sites where ethane δ13C indicated a typical thermogenic origin. At one of the sites in the southern Baikal basin, we found gas hydrates of enclathrated microbial ethane in which 13C and deuterium were both highly depleted (mean δ13C and δD of –61.6‰ V-PDB and –285.4‰ V-SMOW, respectively). To the best of our knowledge, this is the first report of C2 δ13C–δD classification for hydrate-bound gas in either freshwater or marine environments. 相似文献
19.
Tetsuo Yanagi Suhendar I Sachoemar Toshiyuki Takao Shunji Fujiwara 《Journal of Oceanography》2001,57(4):461-470
Intensive hydrographic observations were carried out in the western part of the Gulf of Thailand and the east coastal sea
of Peninsular Malaysia in September 1995 and April–May 1996. The characteristics of seasonal variation of oceanic condition
in that area are discussed basis of an analysis of observed water temperature, salinity and density distributions in these
cruises and NAGA cruises (Yanagi and Takao, 1998a). Stratification is most developed in March–May mainly due to large sea
surface heating and weak sea surface wind, which weakened until September–October, vanishing in December–January. The horizontal
distribution of bottom cold, saline and heavy water masses, which are found during the stratified season, is governed by the
tidal mixing and the water depth. Water exchange between the Gulf of Thailand and the South China Sea becomes large in March–May
due to a coupled effect of the intensified estuarine circulation and the Ekman transport by the southwest monsoon.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
TheEarlySummerSeasonalChangeofLarge-scaleCirculationoverEastAsiaandItsRelationtoChangeofTheFrontalFeaturesandFrontalRainfallE... 相似文献