南海北部陆缘的磁异常特征及居里面深度   总被引：4，自引：0，他引：4  

吴招才  高金耀  赵俐红  张涛  杨春国  王健 《地球科学》2010,35(6):1060-1068

为了研究南海北部张裂大陆边缘的地壳热结构,利用船载测量磁力数据,通过功率谱方法反演南海北部陆缘居里等温面,并结合深地震剖面、区域断裂及大地热流分布,讨论了深部热结构状态.结果显示研究区居里面深度在13~26 km之间,在上下陆坡转换带处与莫霍面相交,北东向断裂多位于居里面梯度带上,北西向断裂多具有分割、错断的特点,居里面深度和大地热流值具有相关性.结果揭示了陆架、上陆坡地区磁性体可能主要位于上地壳和下地壳上部,下陆坡及洋壳区地壳与地幔顶部有被磁化的迹象.磁静区位于居里面上隆区边缘,F3断裂和F4断裂之间可能是残留古洋壳.潮汕凹陷和台西南盆地中央隆起是发生底侵的主要区域,F2断裂为其北界.   相似文献   

局部奇异值分解法压制随机干扰     

陈美年  何兵寿 《中国煤炭地质》2009,(8):51-55

对于低信噪比资料,压制随机噪声,增强有效信号是地震资料处理的首要任务。而传统的奇异值分解去噪算法,在有效信号横向相干性较强时,去噪效果明显,但当有效信号同相轴呈倾斜、弯曲或孤立状态时,其在压制随机噪声的同时,存在滤除部分有效信号的弊端,为此通过对不同时窗内的地震数据进行拉平、奇异值分解数据重构与反拉平等处理方法,对常规奇异值分解算法进行改进,以克服其对包含非水平连续信号资料去噪效果差的局限。理论数据和实际资料的去噪结果表明,改进后的算法去噪效果明显优于常规奇异值分解法,能在保证有效波不被滤除的前提下有效提高地震资料的信噪比。  相似文献   

Middle Triassic post-orogenic extension on Hainan Island: Chronology and geochemistry constraints of bimodal intrusive rocks   总被引：2，自引：0，他引：2  

TANG LiMei  CHEN HanLin  DONG ChuanWan  YANG ShuFeng  SHEN ZhongYue  CHENG XiaoGan  FU LuLu 《中国科学:地球科学(英文版)》2013,(5):783-793

This work studies new petrological and geochemical data and zircon U-Pb ages for bimodal intrusive rocks from Xinglong region, Hainan Island. Zircon U-Pb dating yields mean 238 U/ 206 Pb ages of 238 ± 2 Ma and 234 ± 2 Ma for diabasic and granitic phases, respectively, representing the Middle Triassic emplacement. The diabase and granite bodies were formed from discrete mafic and acidic magma sources that experienced local mechanical mixing at their mutual contacts. Although SiO 2 content of intrusions is bimodal, trace element ratios indicate that both were formed in a post-orogenic extensional setting. Sr-Nd isotopic composition reflects a shared EMII type enriched mantle source component, possibly influenced by subduction-fluid metasomatism.  相似文献   

Magmatism and tectonic processes in Area A hydrothermal vent on the Southwest Indian Ridge   总被引：5，自引：0，他引：5  

ZHANG Tao  LIN Jian  GAO JinYao 《中国科学:地球科学(英文版)》2013,56(12):2186-2197

The hydrothermal vent in Area A(37.78°S,49.65°E)is the first active hydrothermal vent discovered on the Southwest Indian Ridge(SWIR).Heat source and adequate bulk permeability are two necessary factors for the formation of a hydrothermal vent.Along the SWIR 49.3°E to 51.2°E,the gravity-derived crustal thickness is up to 9.0 km,much thicker than the average thickness of the global oceanic crust.This characteristic indicates that the magma supply in this area is robust,which is possibly affected by a hotspot.The large-scale residual mantle Bouguer anomalies(RMBA)reveal prominent negative-gravity anomalies between the first-order ridge segment(from Indomed to Gallieni,46.0°E to 52.0°E)and the Marion-Del Cano-Crozet region.These anomalies indicate the channel of the hotspot-ridge interaction.The tomography data corrected with theoretical thermal model indicate that the low-velocity anomalies corresponding to this channel can reach the base of the lithosphere.Near the hydrothermal vent area,the topography and crustal thickness at the off-axis area are extremely asymmetrical.South of the SWIR,the high topography corresponds to the thinning crustal thickness.The residual isostatic topography anomalies indicate that Area A is a deviation from the local isostatic equilibrium,similar to the characteristics of the transform fault inside corner.The forward profiles of the magnetic data indicate that the thinning magnetic layer at the south side of Area A corresponds to the shallow,high-velocity area revealed by the OBS,which is the result of tectonic extension of a detachment fault.The active tectonic processes in Area A can provide sufficient crustal permeability to the hydrothermal circulation and may form massive sulfide deposits.  相似文献   

Subduction erosion of forearc mantle wedge implicated in the genesis of the South Sandwich Island (SSI) arc: Evidence from boron isotope systematics     

Sonia Tonarini  William P. Leeman  Phil T. Leat 《Earth and Planetary Science Letters》2011,301(1-2):275-284

The South Sandwich volcanic arc is sited on a young oceanic crust, erupts low-K tholeiitic rocks, is characterized by unexotic pelagic and volcanogenic sediments on the down-going slab, and simple tectonic setting, and is ideal for assessing element transport through subduction zones. As a means of quantifying processes attending transfer of subduction-related fluids from the slab to the mantle wedge, boron concentrations and isotopic compositions were determined for representative lavas from along the arc. The samples show variable fluid-mobile/fluid-immobile element ratios and high enrichments of B/Nb (2.7 to 55) and B/Zr (0.12 to 0.57), similar to those observed in western Pacific arcs. δ¹¹B values are among the highest so far reported for mantle-derived lavas; these are highest in the central part of the arc (+ 15 to + 18‰) and decrease toward the southern and northern ends (+ 12 to + 14‰). δ¹¹B is roughly positively correlated with B concentrations and with ⁸⁷Sr/⁸⁶Sr ratios, but poorly coupled with other fluid-mobile elements such as Rb, Ba, Sr and U. Peridotites dredged from the forearc trench also have high δ¹¹B (ca. + 10‰) and elevated B contents (38–140 ppm). Incoming pelagic sediments sampled at ODP Site 701 display a wide range in δ¹¹B (+ 5 to ? 13‰; average = ? 4.1‰), with negative values most common. The unusually high δ¹¹B values inferred for the South Sandwich mantle wedge cannot easily be attributed to direct incorporation of subducting slab materials or fluids derived directly therefrom. Rather, the heavy B isotopic signature of the magma sources is more plausibly explained by ingress of fluids derived from subduction erosion of altered frontal arc mantle wedge materials similar to those in the Marianas forearc. We propose that multi-stage recycling of high-δ¹¹B and high-B serpentinite (possibly embellished by arc crust and volcaniclastic sediments) can produce extremely ¹¹B-rich fluids at slab depths beneath the volcanic arc. Infiltration of such fluids into the mantle wedge likely accounts for the unusual magma sources inferred for this arc.  相似文献   

中印度洋脊Edmond热液区黄铁矿的标型特征及其对海底成矿作用环境的指示   总被引：1，自引：0，他引：1  

王叶剑  韩喜球  金翔龙  邱中炎  朱继浩 《矿物学报》2011,31(2):173-179

对中印度洋脊Edmond热液区的丘顶和丘坡进行电视抓斗取样,获得了大量的金属硫化物等热液作用产物样品。在进行细致的矿相学分析基础上,对硫化物中黄铁矿的标型特征及其演化进行了详细研究。结果表明,Edmond热液区的黄铁矿可分3种类型,其形态标型和成分标型分别具有以下特征:Ⅰ型:呈自形立方体状,S/Fe原子数比接近于2.00,微量元素具有高Cu,低Zn、As、Pb、Ni和Ag的特点,Cu/Zn值高,平均可达4.26;Ⅱ型:呈半自形立方体状,S/Fe原子数比平均2.03,具有高Zn、Co、低Cu的特点,Cu/Zn值(平均0.04)低;Ⅲ型:主要呈胶状、莓球状,S/Fe原子数比平均2.04,具有Ag、Pb、Zn、As元素富集的特点,Cu/Zn值介于前两者之间(平均1.09)。根据硫化物中矿物共生组合关系,认为这3类黄铁矿分别对应高温、中高温和低温成矿作用,黄铁矿的形态和成分能很好地指示热液区的成矿环境和成矿条件的演变。  相似文献   

长江口东南泥质区百年来稀土元素的组成及控制因素     

冯旭文  石学法  黄永祥  许冬  章伟艳  张富元 《地球化学》2011,(5):464-472

在210pb定年的基础上,分析了长江口外东南泥质区柱样沉积物稀土元素含量、特征参数分布特征及其与粒径、常量元素等的相关性,探讨了150 a以来稀土元素的来源、制约因素及对沉积环境的响应.结果表明,柱样稀土元素总量(ΣREE)变化范围不大,分布范围为158.38～197.87 μg/g,平均值为183.49μg/g,总体...  相似文献   

扬子地块北缘晚古生代-早中生代裂谷系统的分布及成因分析   总被引：5，自引：4，他引：1  

毛黎光  肖安成  魏国齐  沈中延  王亮  张林  钱俊锋 《岩石学报》2011,27(3):721-731

晚二叠世长兴期-早三叠世印度期,在扬子地块的西北缘发育了一系列北西向展布的深水盆地区。根据成因分析证实,它们为伸展背景下形成的裂谷系统或者裂谷盆地群。平面上各裂谷盆地彼此近于平行,与北侧的南秦岭造山带在走向上呈正交和大角度斜交的排列,自西向东依次为开江-梁平裂谷、城口-鄂西裂谷和荆门-当阳裂谷。其中的开江-梁平裂谷东西两侧发现了巨大的天然气田而引起石油勘探家和地质学家的关注。本文对于这些控制油气资源储备的裂谷体系的分布和形成机制进行研究后,认为它们形成于南秦岭洋闭合时的碰撞作用,是南秦岭造山带和扬子地块拼合时同生的巨型"碰撞裂谷系统"。  相似文献   

长江河口涨、落潮槽内的沙波地貌和输移特征   总被引：3，自引：0，他引：3       下载免费PDF全文

王永红  沈焕庭  李九发  茅志昌 《海洋与湖沼》2011,42(2):330-336

涨、落潮槽是河口区的重要地貌单元,槽内由于不同的优势流作用而表现出不同的泥沙运移特征。沙波是底沙输移的表现,因此研究槽内的沙波特征对于涨、落潮槽的水动力和沉积地貌研究有重要的意义。本文依据现场声纳观测、测深仪测深、表层取样和现场水动力观测等方法获得河槽床面沙波和水动力资料,对沙波的几何形态、波高和全潮周期的迁移距离进行...  相似文献   

马里亚纳南部弧内坡橄榄岩中的角闪石成分对于弧下地幔交代流体的指示     

董彦辉  初凤友  朱继浩  张平萍 《海洋学报》2011,33(5):91-96

马里亚纳弧前的橄榄岩被认为是SSZ型蛇绿岩的现代等同物,记录了弧下地幔与俯冲流体的交代反应,其中的角闪石被认为是俯冲流体交代的产物.电子探针的数据表明角闪石主要包括透闪石和镁闪石两种,其中前者具有低的钠含量,后者则具有明显高的钠、铝含量,但Mg#较低.角闪石的组成反映了俯冲流体具有高硅、钙、铝、钠等元素的特征.形成成分...  相似文献