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斜向扩张是超慢速扩张洋中脊独特的构造特征,其地形分段特征明显区别于经典的快速-慢速端元洋中脊模型,是理解超慢速扩张洋中脊地质过程的重要切入点。基于西南印度洋中脊Indomed-Gallieni和Shaka-DuToit段多波束地形数据,分析了不同斜向扩张角度(α)洋中脊的地形分段样式。其中,46.5°~47.5°E(α=5°)、16°~25°E(α=10°)和48.5°~52°E(α=15°)为近正向扩张段,发育雁列式叠置的中央火山脊;47.5°~48.5°E(α=50°)和16°~25°E(α=60°)为斜向扩张段,仅在洋脊段中部形成中央火山脊。利用有限差分+颗粒法(FD+MIC)数值模拟技术研究了洋中脊应变分布特征对不同α值的响应,结合地形分析,认为斜向扩张角度和温度异常分布共同控制了洋中脊地形分段样式。近正向扩张洋中脊(α<20°)在温度异常处形成地壳伸展应变的集中区,有利于岩浆汇聚,发育雁列式叠置的中央火山脊,其位置随温度异常分布的变化而改变;斜向扩张洋中脊(α>20°)地壳伸展应变集中区的位置受斜向扩张几何样式控制,在洋脊段中部发育中央火山脊,对温度异常不敏感,形成位置长期固定的岩浆活动中心。 相似文献
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以劳盆地热液羽状流水体为研究对象,对6个不同深度水层(海底以上50~500m)的悬浮颗粒物(>0.45μm)进行了扫描电镜观察和X射线能谱分析。通过颗粒物的微形貌将颗粒物分为生物碎屑、微生物成因颗粒、无定形颗粒和自形颗粒等类型。微生物成因颗粒包括丝状体和簇状体等形态类型;自形颗粒主要为黄铁矿和闪锌矿晶体;根据颗粒组分特征将无定形颗粒分为S-Zn-Ba-Ca、Fe氧化物+少量Ba-Zn-Ca、Fe-Mn-Ca-Ba+少量的Zn、硫化物颗粒及多金属颗粒5种不同类型。大量与热液活动有关的颗粒类型的出现以及无定形颗粒的尺寸分布特征反映了研究站位处于热液羽状流的早期发育阶段,推测在附近几百米范围内存在活动的热液喷口区。 相似文献
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利用气相色谱(GC)、气相色谱-质谱联用仪(GC-MS)测定了西南印度洋中脊49.6°E热液区热液产物中的可溶有机质,结合生物标志物和单体同位素分析,对烃类有机质的组成、来源及成因意义进行了探讨。硫化物烟囱体以正构烷烃(3.437~3.962μg/g)为主要烃类,L/H1,C22以上烷烃具有轻微奇碳数优势(CPI=1.140~1.209),NAR接近0;生物标志物类型丰富(Sq、IS40、烷基环己烷),C31藿烷22S/(R+S)高达0.77,且缺少17β(H),21β(H)构型藿烷;低碳数饱和脂肪酸为主要脂肪酸类型,异构/反异构脂肪酸含量显著,缺少单不饱和脂肪酸。热液蚀变岩以异构烷烃(2.094μg/g)为主要烃类,正构烷烃以低碳数(L/H=1.33)、偶碳优势(CPI=0.377)为特征;脂肪酸以单不饱和脂肪酸为主。结果表明,海洋原生生物体是49.6°E热液区主要的烃类有机质输入源,热液流体温度及化学条件是控制热液喷口区原生生物群落分布及热液产物中烃类有机质组成的主要因素。生物标志物类型显示硫化物烟囱体中具有产甲烷古菌与硫酸盐还原菌共存的现象,反映出热液流体中富含H2,表明49.6°E热液区具有非生物合成烃类的可能。 相似文献
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The ultraslow-spreading Southwest Indian Ridge(SWIR) to the east of the Melville fracture zone is characterized by very low melt supply and intensive tectonic activity. Due to its weak thermal budget and extremely slow spreading rate, the easternmost SWIR was considered to be devoid of hydrothermal activity until the discovery of the inactive Mt. Jourdanne hydrothermal field(27°51′S, 63°56′E) in 1998. During the COMRA DY115-20 cruise in2009, two additional hydrothermal fields(i.e., the Tiancheng(27°51′S, 63°55′E) and Tianzuo(27°57′S, 63°32′E)fields) were discovered. Further detailed investigations of these two hydrothermal sites were conducted by Chinese manned submersible Jiaolong in 2014–2015. The Tiancheng filed can be characterized as a lowtemperature(up to 13.2°C) diffuse flow hydrothermal field, and is hosted by fractured basalts with hydrothermal fauna widespread on the seafloor. The Tianzuo hydrothermal field is an inactive sulfide field, which is hosted by ultramafic rocks and controlled by detachment fault. The discovery of the three hydrothermal fields around Segment #11 which receives more melt than the regional average, provided evidence for local enhanced magmatism providing heat source to drive hydrothermal circulation. We further imply that hydrothermal activity and sulfide deposits may be rather promising along the easternmost SWIR. 相似文献
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