Fission track and fault kinematics analyses for new insight into the Late Cenozoic tectonic regime changes in West-Central Sulawesi (Indonesia)   总被引：1，自引：0，他引：1  

Olivier Bellier  Michel Sbrier  Diane Seward  Thierry Beaudouin  Michel Villeneuve  Eka Putranto 《Tectonophysics》2006,413(3-4):201-220

A 3-D density model for the Cretan and Libyan Seas and Crete was developed by gravity modelling constrained by five 2-D seismic lines. Velocity values of these cross-sections were used to obtain the initial densities using the Nafe–Drake and Birch empirical functions for the sediments, the crust and the upper mantle. The crust outside the Cretan Arc is 18 to 24 km thick, including 10 to 14 km thick sediments. The crust below central Crete at its thickest section, has values between 32 and 34 km, consisting of continental crust of the Aegean microplate, which is thickened by the subducted oceanic plate below the Cretan Arc. The oceanic lithosphere is decoupled from the continental along a NW–SE striking front between eastern Crete and the Island of Kythera south of Peloponnese. It plunges steeply below the southern Aegean Sea and is probably associated with the present volcanic activity of the southern Aegean Sea in agreement with published seismological observations of intermediate seismicity. Low density and velocity upper mantle below the Cretan Sea with ρ  3.25 × 10³ kg/m³ and V_p velocity of compressional waves around 7.7 km/s, which are also in agreement with observed high heat flow density values, point out at the mobilization of the upper mantle material here. Outside the Hellenic Arc the upper mantle density and velocity are ρ ≥ 3.32 × 10³ kg/m³ and V_p = 8.0 km/s, respectively. The crust below the Cretan Sea is thin continental of 15 to 20 km thickness, including 3 to 4 km of sediments. Thick accumulations of sediments, located to the SSW and SSE of Crete, are separated by a block of continental crust extended for more than 100 km south of Central Crete. These deep sedimentary basins are located on the oceanic crust backstopped by the continental crust of the Aegean microplate. The stretched continental margin of Africa, north of Cyrenaica, and the abruptly terminated continental Aegean microplate south of Crete are separated by oceanic lithosphere of only 60 to 80 km width at their closest proximity. To the east and west, the areas are floored by oceanic lithosphere, which rapidly widens towards the Herodotus Abyssal plain and the deep Ionian Basin of the central Mediterranean Sea. Crustal shortening between the continental margins of the Aegean microplate and Cyrenaica of North Africa influence the deformation of the sediments of the Mediterranean Ridge that has been divided in an internal and external zone. The continental margin of Cyrenaica extends for more than 80 km to the north of the African coast in form of a huge ramp, while that of the Aegean microplate is abruptly truncated by very steep fractures towards the Mediterranean Ridge. Changes in the deformation style of the sediments express differences of the tectonic processes that control them. That is, subduction to the northeast and crustal subsidence to the south of Crete. Strike-slip movement between Crete and Libya is required by seismological observations.  相似文献   

使用岭回归对哈萨克斯坦月平均气温的统计降尺度研究     

李亚飞  王磊斌  毛慧琴  延晓冬 《气候与环境研究》2016,21(5):567-576

哈萨克斯坦是世界最大的内陆国家,拥有典型的大陆性气候和多样的地理环境及生态系统,同时哈萨克斯坦的自然环境和人类社会对于气候变化这一全球性问题是敏感的、脆弱的,需要运用科学的研究方法应对气候变化的挑战。通常,区域或局地尺度的气候变化影响研究需要对气候模式输出或再分析资料进行降尺度以获得更细分辨率的气候资料。近年来,大量验证统计降尺度方法在各个地区能力的研究见诸文献,然而在哈萨克斯坦地区验证统计降尺度方法的研究非常少见。本文使用了岭回归的方法对哈萨克斯坦地区11个气象站点1960~2009年的月平均气温进行了统计降尺度研究。结果显示,使用前30年数据和岭回归模型建立大尺度预报因子和观测资料的统计关系可以较好地预测后20年的月平均气温,预测能力在各站各月均有不同程度的差异,地形复杂的站点预测效果较差,夏季预测结果好于冬季;此外,将哈萨克斯坦地区平均来看则与观测数据相吻合。  相似文献   

Paleoproterozoic gabbronoritic and granitic magmatism in the northern margin of the North China craton: Evidence of crust–mantle interaction     

Peng Peng  Jinghui Guo  Mingguo Zhai  Wouter Bleeker 《Precambrian Research》2010

Paleoproterozoic Xuwujia gabbronorites in the northern margin of the North China craton occur as dykes, sills and small plutons intruded into khondalite (aluminous paragneisses, sedimentary protoliths deposited at ca. 2.0–1.95 Ga), and as numerous entrained bodies and fragments of variable scales in the Liangcheng granitoids (ca. 1.93–1.89 Ga). These gabbronoritic dykes are present at all locations where ca. 1.93–1.92 Ga ultra-high-temperature metamorphism is recorded in the khondalite. A gabbronorite sample from the Hongmiaozi dyke gives zircon ²⁰⁷Pb/²⁰⁶Pb mean ages of 1954 ± 6 Ma (core domains) and 1925 ± 8 Ma (rim domains). These ages, as well as previously reported ages, constrain the age of mafic magmatism to be at ca. 1.96–1.92 Ga (∼1.93 Ga). One sample from the Xigou gabbro intruded by the Liangcheng granitoids gives a zircon ²⁰⁷Pb/²⁰⁶Pb mean age of 1857 ± 4 Ma, which is interpreted as the age of a metamorphic overprint. The Xuwujia gabbronorites comprise mainly gabbronorite compositions, as well as some norite, olivine gabbronorite, monzonorite, quartz gabbronorite, and quartz monzonorite. Chemically, they are tholeiitic and can be divided into two groups: a high-Mg group (6.2–22.9 wt.% MgO) and a relatively low-Mg group (2.2–5.7 wt.% MgO). The high-Mg group shows negative Eu-anomalies (Eu/Eu* = 0.53–0.72), slight light rare earth element enrichment (La/Yb_N = 0.56–1.53), and small negative anomalies in high field-strength elements. The ?Nd (t = 1.93 Ga) values vary from +0.3 to +2.4. The low-Mg group shows varied Eu-anomalies (Eu/Eu* = 0.48–1.05), and is enriched in light rare earth elements (La/Yb_N = 1.51–11.98). The majority shows negative anomalies in high field-strength elements (e.g., Th, Nb, Zr, and Ti). Initial ?Nd (at 1.93 Ga) values for low-Mg gabbronorites vary from −5.0 to 0. The Xuwujia gabbronorites possibly experienced assimilation of crust, and fractional crystallization of initially olivine and hypersthene (the high-Mg group), and then olivine, clinopyroxene, and plagioclase (the low-Mg group). The slightly younger Liangcheng granitoids consist of garnet-bearing granite, granodiorite and quartz-rich granitic compositions. They are intermediate to felsic calc-alkaline rocks, thought to be derived from surrounding metasedimentary crust. Xigou gabbro could represent early cumulates. The granitoids have relatively high-Mg numbers (up to 54), and show some chemical affinities with the gabbronorites, which could have resulted from incorporation of gabbronoritic melts. The occurrence and chemical variations of the Xuwujia gabbronorites and Liangcheng granitoids can be interpreted to have resulted from crust–mantle interaction, with mingling and partial mixing of mantle (gabbronoritic) and crustal (granitic) melts. The Xuwujia gabbronorites originated from a mantle region with high potential temperatures (∼1550 °C), possibly associated with a plume or more likely a ridge-subduction-related mantle upwelling event. They could have had extremely high primary intrusion temperatures (up to 1400 °C). Emplacement of these magmas was likely responsible for the extensive crustal anatexis (Liangcheng granitoids) and the local ultra-high-temperature metamorphism. These sequences may have followed ca. 1.95 Ga continent–continent (arc?) juxtaposition and were themselves followed by significant regional uplift and exhumation in the northern margin of the North China craton.  相似文献   

有关断层泥采样与断层位移测量的野外工作方法问题     

王华林  耿杰 《地震研究》1993,16(1):67-72

本文讨论、研究了断层泥采样和断层位移测量的野外工作方法问题。  相似文献   

The Crust of the Western Mediterranean Ridge From Deep Seismic Data and Gravity Modelling   总被引：2，自引：0，他引：2  

C. Truffert  N. Chamot-Rooke  S. Lallemant  B. De  Voogd  P. Huchon  X. Le  Pichon 《Geophysical Journal International》1993,114(2):360-372

  相似文献   

A New Method For Precise Determination of the Position and Strike of Magnetic Boundaries Using Vector Data of the Geomagnetic Anomaly Field   总被引：3，自引：1，他引：3  

Nobukazu Seama  Yoshifumi Nogi  Nobuhiro Isezaki 《Geophysical Journal International》1993,113(1):155-164

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北京冬小麦产量预报的一种建模方案   总被引：3，自引：0，他引：3  

王春乙  潘亚茹  白月明  温民 《气象学报》1994,52(2):223-230

针对农业产量气象预测的各类统计模式中所存在的某些不足，如趋势产量外推的稳定性，预报因子的物理及生物学意义、相关阶段性、多元共线性，回归系数稳定性和剩余产量的处理等，提出了不同的解决办法。在北京冬小麦产量预报试验中收到较好的效果。  相似文献   

Seismic Anisotropy In the Crust At the Mid-Atlantic Plate Boundary In South-West Iceland   总被引：3，自引：0，他引：3  

William Menke  Bryndis Brandsdottir  Steinun Jakobsdottir  Ragnar Stefansson 《Geophysical Journal International》1994,119(3):783-790

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西南印度洋中脊地质构造特征及其地球动力学意义          下载免费PDF全文

余星  迪克·亨利  李小虎  初凤友  董彦辉  胡航 《地球物理学报》1954,63(10):3585-3603

西南印度洋中脊（SWIR）增生的洋壳面积仅占印度洋的15%左右,但其具有比东南印度洋中脊和西北印度洋中脊更悠久而复杂的演化历史.基于已有的地质、地球物理和地球化学等资料,系统总结了SWIR的地质构造特征,并讨论了SWIR的演化过程、洋脊地幔的不均一性、洋脊周边海底高原成因等核心问题.SWIR地形中段高、东西两段低,空间重力异常基本与地形变化一致.按转换断层一级边界可将SWIR划分为20个一级段.SWIR的磁异常条带呈现两端渐进式分布和中段带状分布特征,对应洋脊的三期演化历史.SWIR的地幔源区极不均一,尤其是中新元古代造山带根部集中拆离的中段.源区地幔的不均一性与大陆裂解和洋脊演化过程密切相关.SWIR的东端与西北印度洋中脊和东南印度洋中脊的邻近洋脊段具有地球化学亲缘性,西端与大西洋中脊和南美洲—南极洲洋中脊的邻近洋脊段具有地球化学亲缘性,这与SWIR的渐近式扩张有关.SWIR周边海底高原普遍具有较大的地壳厚度,其成因除了陆壳基底之外,可能与热点火山作用、热点-洋脊相互作用或热点-三联点相互作用有关,目前尚未形成统一的认识.SWIR的形成演化及其作用域内的熔融异常（如海底高原）是冈瓦纳大陆裂解、残留岩石圈地幔、软流圈地幔和深部地幔热柱物质共同作用的结果.了解SWIR的演化过程对揭示冈瓦纳大陆的裂解过程和印度洋的演化具有重要意义.  相似文献   

慢速扩张脊下的复杂熔- 岩相互作用：来自大西洋北纬14°97′区段洋中脊含铬铁矿纯橄岩的记录     

周翔  郑建平  熊庆  刘文龙  Henry J B Dick 《地质学报》2022,96(12):4242-4256

在大西洋洋中脊北纬14°97′附近贫岩浆型慢速扩张脊区段的洋底岩石调查中，拖网取样及洋底钻探均发现蛇纹石化地幔岩石中有脉状纯橄岩。纯橄岩中的铬铁矿粒度以毫米级为主，个别颗粒直径接近厘米级别，成分上显示中等程度的铬值与镁值(Cr#=52. 2~56. 1；Mg#=44. 6~51. 5)较高的TiO2含量(0. 60% ～0. 91%)。铬铁矿内部包裹体中大量出现韭闪石+金云母组合，并发现自形磷灰石包裹体。这些特征与“俯冲带型铬铁矿”的成分特征及矿物包裹体组合非常类似。本文的样品观察说明在洋中脊下方的熔体通道内，高度演化的熔体可以形成小体积的富水岩浆并参与铬铁矿的形成。拖网调查与钻探研究证实，研究区的纯橄岩、异剥橄榄岩、富橄榄石橄长岩、辉石岩、辉长岩及橄榄辉长岩等均以脉体形式产于难熔的大洋岩石圈橄榄岩质地幔中。这些脉状岩石共同记录了洋中脊玄武质熔体向上迁移过程中与围岩方辉橄榄岩间的熔- 岩反应，属于“交代橄榄岩”的范畴，揭示了慢速扩张洋脊之下熔体迁移诱发的复杂熔- 岩相互作用。  相似文献