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SUN Chaofeng,WU Zhaocai,TAO Chunhui,RUAN Aiguo,ZHANG Guoyin,GUO Zhikui,HUANG Enxian. 2018. The deep structure of the Duanqiao hydrothermal field at the Southwest Indian Ridge. Acta Oceanologica Sinica, 37(3):73－79

The deep structure of the Duanqiao hydrothermal field at the Southwest Indian Ridge

西南印度洋脊“断桥”热液区深部地质构造研究

Received:April 24, 2016 Revised:January 01, 2017

DOI：10.1007/s13131-017-0986-2

Key words:crustal thickness Duanqiao hydrothermal field gravity anomaly polymetallic sulfides Southwest Indian Ridge

中文关键词: 地壳厚度断桥热液区重力异常多金属硫化物西南印度洋脊

基金项目:The National Basic Research Program (973 Program) of China under contract No. 2012CB417305; the China Ocean Mineral Resources Research and Development Association Twelfth Five-Year Major Program under contract Nos DY125-11-R-01 and DY125-11-R-05; the International Cooperative Study on Hydrothermal System at Ultraslow Spreading SWIR; the Natural Science Foundation of Zhejiang Province of China under contract No. LY12D06006; the Scientific Research Fund of Second Institute of Oceanography, State Oceanic Administration under contract No. JG1203.

Author Name	Affiliation	E-mail
SUN Chaofeng	Key Laboratory of Submarine Geosciences, State Oceanic Administration, Hangzhou 310012, China Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China
WU Zhaocai	Key Laboratory of Submarine Geosciences, State Oceanic Administration, Hangzhou 310012, China Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China
TAO Chunhui	Key Laboratory of Submarine Geosciences, State Oceanic Administration, Hangzhou 310012, China Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China	taochunhuimail@163.com
RUAN Aiguo	Key Laboratory of Submarine Geosciences, State Oceanic Administration, Hangzhou 310012, China Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China
ZHANG Guoyin	Key Laboratory of Submarine Geosciences, State Oceanic Administration, Hangzhou 310012, China Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China
GUO Zhikui	Key Laboratory of Submarine Geosciences, State Oceanic Administration, Hangzhou 310012, China Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China Institute of Geophysics and Geomatics, China University of Oceanography, Wuhan 430074, China
HUANG Enxian	Henan Province Earthquake Administration, Zhengzhou 450016, China

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Abstract:

Polymetalic sulfide is the main product of sea-floor hydrothermal venting, and has become an important sea-floor mineral resources for its rich in many kinds of precious metal elements. Since 2007, a number of investigations have been carried out by the China Ocean Mineral Resources Research and Development Association (COMRA ) cruises (CCCs) along the Southwest Indian Ridge (SWIR). In 2011, the COMRA signed an exploration contract of sea-floor polymetallic sulfides of 10 000 km² on the SWIR with the International Seabed Authority. Based on the multibeam data and shipborne gravity data obtained in 2010 by the R/V Dayang Yihao during the leg 6 of CCCs 21, together with the global satellite surveys, the characteristics of gravity anomalies are analyzed in the Duanqiao hydrothermal field (37°39'S, 50°24'E). The “subarea calibration” terrain-correcting method is employed to calculate the Bouguer gravity anomaly, and the ocean bottom seismometer (OBS) profile is used to constrain the two-dimensional gravity anomaly simulation. The absent Moho in a previous seismic model is also calculated. The results show that the crustal thickness varies between 3 and 10 km along the profile, and the maximum crustal thickness reaches up to 10 km in the Duanqiao hydrothermal field with an average of 7.5 km. It is by far the most thicker crust discovered along the SWIR. The calculated crust thickness at the Longqi hydrothermal field is approximately 3 km, 1 km less than that indicated by seismic models, possibly due to the outcome of an oceanic core complex (OCC).

中文摘要:

多金属硫化物是海底热液活动的主要产物，因其富含多种贵金属元素，成为一种重要的海底矿产资源。2007年以来，中国大洋调查航次在西南印度洋脊开展了多个航次的海底热液活动调查。并于2011年，中国大洋矿产资源研究开发协会与国际海底管理局签署了西南印度洋脊一万平方公里的多金属硫化物勘探合同。利用2010年DY115-21航次第六航段多波束数据及船测重力数据以和全球卫星数据，分析了西南印度洋中国多金属硫化物勘探合同区内“断桥”热液区（点）（50°24'E ，37°39'S）的重力异常特征，采用“分区校正”地形改正方法计算了布格重力异常，并以OBS剖面结构为约束，进行了重力异常2-D模拟。计算出了地震反演结果中缺失的Moho面。结果发现沿剖面地壳厚度变化在3-10km之间；“断桥”热液区地壳最厚处达10km，平均厚度在7.5km左右，是目前为止在西南印度洋中脊上发现的最厚地壳；“龙旂”热液区地壳厚度约3km，对比地震结果要薄1km，可能受到周围OCC比较薄的影响。认为“断桥”热液区为海底多金属硫化物成矿有利地带。

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