南海神狐海域沉积物自生黄铁矿和石膏S同位素特征及对甲烷渗漏强度的示踪   总被引：1，自引：1，他引：0  

张美  陆红锋  管红香  刘丽华  邬黛黛  吴能友 《海洋学报(英文版)》2018,37(7):20-27

The northern slope of the South China Sea is a gas-hydrate-bearing region related to a high deposition rate of organic-rich sediments co-occurring with intense methanogenesis in subseafloor environments.Anaerobic oxidation of methane(AOM) coupled with bacterial sulfate reduction results in the precipitation of solid phase minerals in seepage sediment,including pyrite and gypsum.Abundant aggregates of pyrites and gypsums are observed between the depth of 667 and 850 cm below the seafloor(cmbsf) in the entire core sediment of HS328 from the northern South China Sea.Most pyrites are tubes consisting of framboidal cores and outer crusts.Gypsum aggregates occur as rosettes and spheroids consisting of plates.Some of them grow over pyrite,indicating that gypsum precipitation postdates pyrite formation.The sulfur isotopic values(δ~(34) S) of pyrite vary greatly(from –46.6‰ to –12.3‰ V-CDT) and increase with depth.Thus,the pyrite in the shallow sediments resulted from organoclastic sulfate reduction(OSR) and is influenced by AOM with depth.The relative high abundance and δ~(34) S values of pyrite in sediments at depths from 580 to 810 cmbsf indicate that this interval is the location of a paleo-sulfate methane transition zone(SMTZ).The sulfur isotopic composition of gypsum(from–25‰ to –20.7‰) is much lower than that of the seawater sulfate,indicating the existence of a 34 S-depletion source of sulfur species that most likely are products of the oxidation of pyrites formed in OSR.Pyrite oxidation is controlled by ambient electron acceptors such as MnO_2,iron(Ⅲ) and oxygen driven by the SMTZ location shift to great depths.The δ~(34) S values of gypsum at greater depth are lower than those of the associated pyrite,revealing downward diffusion of 34 S-depleted sulfate from the mixture of oxidation of pyrite derived by OSR and the seawater sulfate.These sulfates also lead to an increase of calcium ions from the dissolution of calcium carbonate mineral,which will be favor to the formation of gypsum.Overall,the mineralogy and sulfur isotopic composition of the pyrite and gypsum suggest variable redox conditions caused by reduced seepage intensities,and the pyrite and gypsum can be a recorder of the intensity evolution of methane seepage.  相似文献   

南黄海崂山隆起中、古生界油气保存条件分析     

许振强  梁杰  陈建文  张鹏辉  张银国  王建强  雷宝华  杨传胜 《海洋地质与第四纪地质》2018,(3)

崂山隆起位于南黄海盆地中部,海相中-古生界分布广泛且厚度大,其构造演化经历了加里东、海西、印支、燕山和喜山等多期构造运动,早期油气聚集可能在后期受到不同程度的破坏,因此,油气保存条件是崂山隆起油气勘探能否取得突破的关键因素。通过综合分析构造运动中抬升剥蚀作用和断裂作用与油气保存的关系,以及盖层条件与油气保存的关系,探讨崂山隆起内部油气保存条件的差异性以指导该区油气勘探。结果表明:崂山隆起呈差异性油气保存特点,位于崂山隆起中南部的高石稳定带是一个早期断裂不发育的弱变形区,后期构造运动改造破坏程度较弱,特别是下古生界具备较为优越的生储盖组合,构造多以断背斜和低幅宽缓背斜为主,发育多个大型圈闭,岩浆活动相对较弱,油气保存条件较为优越;而崂山隆起北部的青峰变形带断裂系统发育,地层褶皱变形强烈,单个圈闭规模较小,油气保存条件相对较差;高石稳定带中南部是进一步油气勘探和调查参数井钻探的重点目标区。  相似文献   

Smectite formation in metalliferous sediments near the East Pacific Rise at 13°N   总被引：1，自引：0，他引：1  

荣坤波  曾志刚  殷学博  陈帅  王晓媛  齐海燕  马瑶 《海洋学报(英文版)》2018,37(9):67-81

A 43 cm long E271 sediment core collected near the East Pacific Rise(EPR) at 13°N were studied to investigate the origin of smectite for understanding better the geochemical behavior of hydrothermal material after deposition.E271 sediments are typical metalliferous sediments. After removal of organic matter, carbonate, biogenic opal,and Fe-Mn oxide by a series of chemical procedures, clay minerals(2 μm) were investigated by X-ray diffraction,chemical analysis and Si isotope analysis. Due to the influence of seafloor hydrothermal activity and close to continent, the sources of clay minerals are complex. Illite, chlorite and kaolinite are suggested to be transported from either North or Central America by rivers or winds, but smectite is authigenic. It is enriched in iron, and its contents are highest in clay minerals. Data show that smectite is most likely formed by the reaction of hydrothermal Fe-oxyhydroxide with silica and seawater in metalliferous sediments. The Si that participates in this reaction may be derived from siliceous microfossils(diatoms or radiolarians), hydrothermal fluids, or detrital mineral phases. And their δ30 Si values are higher than those of authigenic smectites, which implies that a Si isotope fractionation occurs during the formation because of the selective absorption of light Si isotopes onto Feoxyhydroxides. Sm/Fe mass ratios(a proxy for overall REE/Fe ratio) in E271 clay minerals are lower than those in metalliferous sediments, as well as distal hydrothermal plume particles and terrigenous clay minerals. This result suggests that some REE are lost during the smectite formation, perhaps because their large ionic radii of REE scavenged by Fe-oxyhydroxides preclude substitution in either tetrahedral or octahedral lattice sites of this mineral structure, which decreases the value of metalliferous sediments as a potential resource for REE.  相似文献   

泥质烃源岩酸解有机质中两环倍半萜的检出及其意义     

《东北石油大学学报》2018,(2)

以东营凹陷沙三下亚段和沙四上亚段主力烃源岩为研究对象,采用有机溶剂抽提—HCl酸解连续处理实验方法,对泥质烃源岩黏粒级组分的游离态有机质和碳酸盐矿物结合态有机质进行地球化学表征。结果表明:游离态有机质可以提供沉积环境、热成熟度、有机质生源等地化信息,碳酸盐矿物结合态有机质能补充有机质生源信息;碳酸盐矿物结合态有机质能更好地保存烃类组分的轻质端,可以指示Botryococcus braunii生源的两环倍半萜类生物标志化合物仅在赋存态中检出。此外单质硫具有相对较高的丰度,相对封闭的矿物晶格赋存环境使有机质的原生地质信息更好地保留下来。对烃源岩中游离态有机质和矿物结合态有机质的综合分析,可以得到更为真实客观的地质推断结果。  相似文献   

山东半岛南部近岸海域碎屑矿物对中小河流的物源响应     

宁泽  韩宗珠  林学辉  张勇  毕世普  孔祥淮  刘金庆 《海洋地质前沿》2019,35(4):57-68

对山东半岛南部近岸海域的106个表层沉积物样品及大沽河、五龙河和乳山河的94个表层沉积物样品进行碎屑矿物分析,系统地研究了碎屑矿物的分布特征及物源指示。研究区共鉴定出40种重矿物和13种轻矿物,重矿物以普通角闪石、绿帘石、黑云母和自生黄铁矿为主,轻矿物以石英、斜长石、钾长石和风化云母为主。根据碎屑矿物组合特征,将研究区分为4个矿物区:Ⅰ区为胶州湾口至崂山头的附近海域;Ⅱ_1亚区为丁字湾和鳌山湾附近水深约15m以浅的海域,Ⅱ_2亚区为研究区东南部水深20m的远岸区;Ⅲ区处于Ⅱ区和Ⅳ区的过渡带;Ⅳ区为乳山口西南部近岸海域。Ⅰ区和Ⅱ区的矿物组合均为普通角闪石-绿帘石-石英-长石,Ⅰ区和Ⅱ_1亚区受大沽河、五龙河和乳山河输入的物质及沿岸基岩、岛屿风化碎屑的影响较大,Ⅱ_2亚区主要为晚更新世低海平面时形成的陆架残留沉积。Ⅲ区矿物组合为普通角闪石-石英-长石-片状矿物,Ⅳ区矿物组合为云母类-自生黄铁矿-普通角闪石-石英,Ⅲ区、Ⅳ区物源多样,黄河物质对两区贡献显著。  相似文献   

探索墨西哥湾深水沉积的超高压和流体流动过程与机理--IODP308航次钻探成果     

李前裕  蒋少涌 《海洋地质与第四纪地质》2006,26(3):6-8

墨西哥湾深水区发育有典型的浊流沉积，长期以来就以独特的被动边缘浊积类型闻名于世。由密西西比河带来的大量碎屑物在河口外形成巨厚泥砂层，快速沉积造成上陆坡特别不稳定，所以塌坡或崩塌事件经常发生，引起迭繁的浊流活动。松散的浅水碎屑物往往随浊流被搬运到陆坡或更深的深水区，造成大规模的再沉积。塌坡事件及其引发的浊流活动存在较大的随机性及其对沉积物造成的分选性，直接控制了墨西哥湾深水区沉积物中的流体流动以至油气生成，使其成为目前世界上富含油气的三大海区之一。但沉积砂层所伴生的超高压常常造成“井喷”，使油气探采难度加大，成本增高，连年来使有关石油公司损失惨重，也给科学界提出了急需解决的科学问题。为什么墨西哥湾深水区超高压现象这么普通？超高压区的流体流动规律有什么特征？它受什么机理控制？浊流沉积跟气候变化有联系吗？是否受冰期／间冰期旋回的影响？  相似文献   

琉球群岛东部海区表层沉积物中浮游有孔虫分布及指示意义     

吴永华  程振波  石学法  李小艳  石丰登  鞠小华 《海洋地质与第四纪地质》2007,27(6):1-7

对琉球群岛东部海区123个表层沉积物样品中浮游有孔虫因子分析结果表明,浮游有孔虫组合在溶跃面以上表现为Globigerinoides ruber-Globigerinata glutinata组合,溶跃面以下为Globorotalia inflata-Neoglobo-quadrina pachyderma (dex.)组合,局部受黑潮影响区域黑潮标志种Pulleniatina obliquiloculata含量相对丰富,为Neogloboquadrina dutertrei-P.obliquiloculata组合;表层沉积物中浮游有孔虫的丰度及组合分布特征对于碳酸盐溶跃面深度及碳酸盐补偿深度有一定的指示意义。另外,碳酸盐保存特征研究表明,该区域现代碳酸盐溶跃面深度约为3100 m,碳酸盐补偿深度约为4300 m。  相似文献   

两种碎屑沉积物分类方法的比较   总被引：3，自引：0，他引：3  

王中波  杨守业  张志珣 《海洋地质前沿》2007,23(3):36-40

全面地介绍和对比Shepard和Folk两种沉积物分类方法及图解的原理及其适用性,分析其优缺点。相对Shepard分类方法而言,Folk分类图解更简洁、更实用,其分类边界划分更客观,从而能更好地揭示沉积物特征。建议在国内沉积学研究及正在开展的海洋地质大调查中统一使用Folk沉积物分类方法,不仅可以更好的研究沉积物特征及其分布规律,而且对促进国内外学术交流具有一定意义。  相似文献   

南海南部近50万年来沉积物特点及古环境意义     

梅西  郑洪波  黄恩清  陈国成  谢昕 《海洋地质与第四纪地质》2007,27(4):77-84

对南海南部MD05-2897孔沉积物的分析显示,该孔涵盖氧同位素1~12期,底界年龄约为50万年。碳酸钙含量曲线形态基本与底栖有孔虫氧同位素曲线平行,即碳酸钙高值对应氧同位素轻值,呈现典型的大西洋型碳酸钙分布模式。碳酸钙含量在冰消期的高值出现及含量变化均领先于氧同位素,证明低纬海区"碳酸钙泵"对大气二氧化碳浓度和温度的作用。粒度分析显示,3~5μm组分含量曲线的变化与氧同位素曲线基本平行,说明它主要受海平面升降变化控制,可作为海平面变化的间接指标。而1.5~2.5μm粒级颗粒主要通过河流的悬浮搬运,直接受亚洲夏季风及其所带来降雨的影响,可间接反映夏季风的强弱变化。南海南部深海沉积中的季风记录具有0.1 Ma偏心率周期,40 ka斜率周期,20 ka岁差和10 ka半岁差周期等丰富的频谱,显示出低纬度海区气候变化对轨道周期的良好响应。  相似文献   

越南岸外上升流区48万年来高分辨率的生源组分记录及其古海洋学意义   总被引：1，自引：1，他引：1  

向霏  王汝建  李建如  叶芳 《海洋地质与第四纪地质》2006,26(6):81-89

南海西部越南岸外MD05-2901孔沉积物分析显示,该孔覆盖氧同位素1-12期,底界年龄约为48万年。生源组分记录显示表层古生产力冰期高、间冰期低,体现间冰期海平面下降、陆源物质输入增强的影响。生产力在末次冰期达到最高,体现末次盛冰期海陆差异增强,东北风发育对生产力提高的促进作用。碳酸钙含量变化呈现冰期早期含量低、冰消期和间冰期含量高的趋势。其冰消期的高值在MIS1/2、MIS3/4和MIS5/6分界处,与浮游有孔虫碳同位素低值对应,揭示该地区的碳酸钙沉积旋回是“稀释旋回”。同时碳酸钙含量变化领先于同一地区浮游有孔虫氧同位素的变化,证明低纬海区碳酸钙泵作用对大气二氧化碳浓度和温度有影响。滤波分析结果显示碳同位素存在23 ka的岁差周期和偏心率长周期,生源组分的含量变化显示出典型的岁差周期,体现南海季风环流的轨道响应,证明低纬热带过程是调节气候变化的重要因素。  相似文献