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991.
992.
通过对内蒙古额济纳盆地小狐山剖面沉积物中酸溶组分稀土元素含量及其相关指标、分布模式的分析,讨论了剖面中稀土元素指标δCe-ΣREE与沉积相、沉积环境之间的关系。分析结果表明剖面沉积物酸溶组分中稀土元素丰度均值为7.24μg/g(不包括Y),其中LREE含量占稀土总量的88.67%; 且各层的稀土分布模式均为轻稀土适度富集缓右倾斜型、Eu呈负异常模式,但各相位地层的LREE富集程度与分配模式存在差异。由于小狐山剖面中沉积地层的自身岩性、沉积粒径、矿物结构组成以及气候环境变化等因素均可能会引起REE分异。因此,通过δCe-ΣREE图并结合三次回归曲线,可以很好地将不同沉积相得物质有效的区分开来。小狐山剖面除极少数的几个样品(水下沉积砂)之外,其余的均落在三次多项式回归曲线上部; 而风成砂层则几乎全部落在回归曲线之下; 此外,对于风沙-河流作用下的混合样品也有较好识别,河流过渡相的样品则分布在曲线上或与之相邻近。此研究结果得到了柴达木贝壳堤沉积物的REE数据的验证,运用此方法可以为直观的判别剖面中的不同沉积相,并为定量化划分地层提供依据。 相似文献
993.
Based on the deformation characteristics of the ductile shear zones in Sumdo (松多) Group, the quartz fabric by EBSD (electron backscatter diffraction), the data of muscovite 40Ar-39Ar geochronology (220-230 Ma) from ductile shear zones and the zircon SHRIMP U-Pb chronology (190 Ma) of granites in Snmdo region, Lhasa (拉萨) terrane is thought to have experienced an important Indosinian orogenic event at 220-230 Ma, which caused the closure of the paleo-Tethys Ocean along the tectonic zone of eclogite and the collision between northern part and southern part of the Lhasa terrane. The zircon SHRIMP U-Pb chronology of 190 Ma for biotite adamellite, with the distributing characteristics of the granite massif intruding in Sumdo Group, indicates that the biotite adamellitc should be the late orogenic or post-orogenic granite resulting from the lndosinian orogenesis. The discovery of Indosinian orogenic belt in Lhasa terrane expansed the southern boundary of lndosinian orogenic belt in Qinghai (青海)-Tibet plateau to Lhasa terrane from Qiangtang (羌塘) terrane, which changed the understanding about the distribution of Indosinian orogenic belt in Qinghai-Tibet plateau and extended the "T" type lndosinian orogenic belt in China. The study is very important for the formation and distribution of paleo-Tethys Ocean in Tibet. The ancient terrane framework and evolution of Qinghai-Tibet plateau need further research. 相似文献
994.
牛场组--上扬子区南部志留系兰多维列统的一个新地层单位 总被引:1,自引:1,他引:0
志留纪初的扬子海底域大都被缺氧水占据 ,黑色笔石页岩 (称龙马溪组 )广泛发育 ,底栖生物难以存活 ;但表层水域仍然充氧 ,是笔石等生物的生活场所。在上扬子海南缘的近岸、浅水区 (贵州北部 )繁衍了腕足动物及三叶虫等壳相生物 ,笔石稀少或缺失。相关地层长期被笼统地归于龙马溪组而没有其他名称。现以贵州湄潭牛场高滩剖面为依据 ,将该地原归“龙马溪组”的地层新建为牛场组 ,按全国地层委员会的最新要求 ,描述命名剖面 (地理位置、岩性特征、生物组合、顶、底界线、厚度、横向延展、与上覆、下伏地层的接触关系等 ) ,讨论它与相关地层的区别与对比等。牛场组底部因发现笔石而确定了地层位置 ;其顶界因尚未发现可资肯定时代的化石 ,只是根据区域对比推测其时代归属。研究结果表明 ,牛场组代表兰多维列 (L landovery)世早—中期、黔中古陆以北近岸、充氧、浅水的非笔石相地层 ,在黔北遵义、湄潭、思南一带发育 ,这一适宜于底栖生物生存的正常浅海环境为大灭绝后壳相生物的复苏与辐射提供了基本条件。与牛场组相当的地层包括标准龙马溪组下部的一部分和标准香树园组的下部 ,前者以黑色笔石页岩为特征 ,后者以瘤状泥灰岩、泥质灰岩为主。 相似文献
995.
996.
苏盖特构造带位于新疆昆仑山弧形推覆体前缘.本文通过研究苏盖特构造带的构造特征,确定了地震反射层的地质属性,认为苏盖特构造带由表层推覆体及下部下第三系-二叠系之间的地层经过3次重复形成的叠瓦状推覆体构成.苏盖特构造带活动始于上新世阿图什组沉积期,定型于更新世.通过研究西昆仑逆冲推覆体及已钻探井的地表油源、储层特征及储盖组合,认为苏盖特构造带具有两套好的油源即石炭-二叠系及侏罗系油源,两套好的储集层即白垩系和下第三系储层,相应地,发育两套储盖组合,具有良好的圈闭及运聚条件,是有利的勘探目标区. 相似文献
997.
O. Vaduvescu M. Birlan A. Tudorica A. Sonka F.N. Pozo A.D. Barr D.J. Asher J. Licandro J.L. Ortiz E. Unda-Sanzana M. Popescu A. Nedelcu D. Dumitru R. Toma I. Comsa C. Vancea D. Vidican C. Opriseanu T. Badescu M. Badea M. Constantinescu 《Planetary and Space Science》2011,59(13):1632-1646
We report on the follow-up and recovery of 100 program NEAs, PHAs and VIs using the ESO/MPG 2.2 m, Swope 1 m and INT 2.5 m telescopes equipped with large field cameras. The 127 fields observed during 11 nights covered 29 square degrees. Using these data, we present the incidental survey work which includes 558 known MBAs and 628 unknown moving objects mostly consistent with MBAs from which 58 objects became official discoveries. We planned the runs using six criteria and four servers which focus mostly on faint and poorly observed objects in need of confirmation, follow-up and recovery. We followed 62 faint NEAs within one month after discovery and we recovered 10 faint NEAs having big uncertainties at their second or later opposition. Using the INT we eliminated four PHA candidates and VIs. We observed in total 1286 moving objects and we reported more than 10,000 positions. All data were reduced by the members of our network in a team effort, and reported promptly to the MPC. The positions of the program NEAs were published in 27 MPC and MPEC references and used to improve their orbits. The O−C residuals for known MBAs and program NEAs are smallest for the ESO/MPG and Swope and about four times larger for the INT whose field is more distorted. For the astrometric reduction, the UCAC-2 catalog is recommended instead of USNO-B1. The incidental survey allowed us to study statistics of the MBA and NEA populations observable today with 1–2 m facilities. We calculate preliminary orbits for all unknown objects, classifying them as official discoveries, later identifications and unknown outstanding objects. The orbital elements a, e, i calculated by FIND_ORB software for the official discoveries and later identified objects are very similar with the published elements which take into account longer observational arcs; thus preliminary orbits were used in statistics for the whole unknown dataset. We present a basic model which can be used to distinguish between MBAs and potential NEAs in any sky survey. Based on three evaluation methods, most of our unknown objects are consistent with MBAs, while up to 16 unknown objects could represent NEO candidates and four represent our best NEO candidates. We assessed the observability of the unknown MBA and NEA populations using 1 and 2 m surveys. Employing a 1 m facility, one can observe today fewer unknown objects than known MBAs and very few new NEOs. Using a 2 m facility, a slightly larger number of unknown than known asteroids could be detected in the main belt. Between 0.1 and 0.8 new NEO candidates per square degree could be discovered using a 2 m telescope. 相似文献
998.
SHRIMP zircon U–Pb geochronological, elemental and Sr–Nd isotopic data from Early Cretaceous mafic dykes in North Dabie orogenic belt elucidate a change of Mesozoic lithospheric mantle in eastern China. The dykes are predominantly dolerite with the major mineral assemblage clinopyroxene + hornblende + plagioclase and yield a SHRIMP zircon U–Pb age of 111.6 ± 5.3 Ma. They have a narrow range of SiO2 from 46.16% to 49.78%, and relative low concentrations of K2O (1.07−2.62%), Na2O (2.45−3.54%), Al2O3 (13.04−14.07%), and P2O5 (0.42−0.55%) but relatively high concentration of MgO (5.94–6.61%) with Mg# 52–54. All the samples are characterized by enrichment of large ion lithophile elements (LILE, e.g., Ba, Th) and high field strength elements (HFSE, e.g., Nb, Ti). (87Sr/86Sr)i ratios from 0.704 to 0.705, εNd values from 3.36 to 4.33 and mantle‐depletion Nd model ages (T2DM) in the range 0.56–0.64 Ga indicate that the magma of the Baiyashan mafic dykes was derived from a young depleted mantle source. This finding is different from previous research on mafic dykes in the age range 120–138 Ma that revealed enrichment of LILE and depletion of HFSE, high initial Sr isotopic ratios and negative εNd, value which represents an old enriched mantle source. Ours is the first report of the existence of Early Cretaceous depleted mantle in eastern China and it implies that changing of enriched mantle to depleted mantle occurred at ca. 112 Ma, associated with back‐arc extension which resulted from the subduction of the Palaeo‐Pacific Plate towards the Asian Continent. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
999.
渤海古近系东营组三角洲相油田是渤海油田的主力含油层系.从构造、储层与沉积、流体和油藏等方面对渤海海域东营组三角洲相油田地质特征进行了研究,按河流三角洲和辫状河三角洲相砂岩油藏两种沉积相类型分别对储层分布特征进行了描述.在此基础上探讨了此类油田的流体分布特点和油藏模式,并认为渤海东营组三角洲相油田以中到大型为主,储层岩性大都属于高孔高渗的疏松砂岩,储层具有分布较稳定、油层厚和物性好等特点,原油以普通稠油为主,其次是中、低黏油. 相似文献
1000.