南海东北部大陆坡地震反射异常体的属性分析与岩性识别*
李博安(1995—), 男, 广东省韶关市人, 硕士研究生, 从事海洋地质与地球物理研究。email: |
Copy editor: 姚衍桃
收稿日期: 2021-03-03
修回日期: 2021-04-07
网络出版日期: 2021-04-13
基金资助
中国科学院青年创新促进会(Y202076)
南方海洋科学与工程广东省实验室(广州)人才团队引进重大专项(GML2019ZD0204)
南方海洋科学与工程广东省实验室(广州)人才团队引进重大专项(GML2019ZD0104)
中国科学院南海海洋研究所“南海新星”Ⅰ类(NHXX2019DZ0101)
广东省特支计划(2019BT02H594)
国家自然科学基金(U1901217)
国家自然科学基金(91855101)
国家自然科学基金(41876052)
Property analysis and lithology identification of seismic reflection anomalies on the continental slope of northeastern South China Sea
Copy editor: YAO Yantao
Received date: 2021-03-03
Revised date: 2021-04-07
Online published: 2021-04-13
Supported by
Youth Innovation Promotion Association Chinese Academy of Sciences(Y202076)
Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou)(GML2019ZD0204)
Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou)(GML2019ZD0104)
Rising Star Foundation of the South China Sea Institute of Oceanology(NHXX2019DZ0101)
Special Support Program for Cultivating High-level Talents in Guangdong Province(2019BT02H594)
National Natural Science Foundation of China(U1901217)
National Natural Science Foundation of China(91855101)
National Natural Science Foundation of China(41876052)
南海北缘属于非火山型大陆边缘。过去的研究在洋陆转换带北部的地震剖面上曾观测到一些疑似岩席和火山体的高振幅异常体, 但对这些高振幅异常体的属性却缺乏进一步的研究。本文在南海东北部大陆坡上的两个多道地震剖面(SO1E和SOY)中也发现了一个长度超过15km、厚度约为1.2km的巨大高振幅异常体, 它为研究者提供了一个探究洋陆转换带北部是否存在岩浆活动的机会。本研究对该高振幅异常体进行了速度分析与AVO(amplitude variation with offset)分析。结果表明, 与周围岩层相比, 该高振幅异常体内部有较高的P波速度和泊松比。结合区域地质背景和异常体内部的反射特征及大小形状, 推测该高振幅异常体为火成侵入岩, 并将其进一步归类为岩盖, 揭示了中新世以后南海北部洋陆转换带北部曾发生过多期次的岩浆活动。
李博安 , 胡善政 , 阎贫 , 于俊辉 , 王潇 , 唐群署 . 南海东北部大陆坡地震反射异常体的属性分析与岩性识别*[J]. 热带海洋学报, 2022 , 41(1) : 204 -214 . DOI: 10.11978/2021028
The northern margin of the South China Sea (SCS) is often regarded as a magma-poor passive continental margin. Many high amplitude anomalies were observed in previous studies on seismic profiles at the northern part of the Continent-Ocean Transition (COT) in the northern SCS, and were interpreted as sills and volcanos. However, further investigation on the properties of these high amplitude anomalies was lacking. In this study, we observed a large anomaly with a thickness of ~1.2 km in two multi-channel seismic profiles (SO1E and SOY) on the northeastern continental slope of the SCS. This provides an opportunity to determine the presence of magmatic activities north of the COT. Velocity analysis and AVO (amplitude variation with offset) analysis were performed for the large-amplitude anomaly. Results show that the high-amplitude anomaly has a higher P wave velocity and Poisson’s ratio than the host strata above. Considering the regional geologic background, the internal reflection characteristics, spatial size and shape of this high-amplitude anomaly, we suggest that the high-amplitude anomaly can be characterized as an igneous rock and further classified as a laccolith. This also indicates that multi-phase magmatism occurred north of the COT since the Miocene.
Key words: northeastern South China Sea; laccolith; velocity analysis; AVO analysis
图1 研究区(a)及测线(b)位置示意图图a Locations of the study area (a) and seismic lines (b). (a) The area between two brown curves represents the Continent-Ocean Transition (COT) (Wang et al, 2006). Red ellipses represent seamounts (Fan et al, 2017). (b) Black lines represent two multi-channel seismic lines SO1E and SOY used in this study. Yellow circles and a ellipse represent the high-amplitude anomalies observed in previous studies and this study, respectively |
图5 CDP号为14850~17851的地震剖面(a)与精细速度场(b)Fig. 5 Seismic profile (a) and interval velocity field (b) between CDPs 14850~17851 |
表1 SO1E测线1#—5#CDP上4个拾取点的速度Tab. 1 Velocities at CDPs 1#~5# of Line SO1E |
CDP | 点号 | 时间/ms | 叠加速度/(m•s-1) | 层速度/(m•s-1) |
---|---|---|---|---|
1# | ① | 1915 | 1502 | 1874 |
② | 2370 | 1581 | 2387 | |
③ | 3195 | 1845 | 2977 | |
④ | 3485 | 1960 | 3207 | |
2# | ① | 1924 | 1503 | 1828 |
② | 2419 | 1577 | 2381 | |
③ | 3264 | 1820 | 3270 | |
④ | 3586 | 1996 | 3282 | |
3# | ① | 2173 | 1504 | 1890 |
② | 2725 | 1590 | 2546 | |
③ | 3305 | 1798 | 3692 | |
④ | 3773 | 2128 | 3370 | |
4# | ① | 2188 | 1503 | 1850 |
② | 2763 | 1586 | 2404 | |
③ | 3310 | 1747 | 3601 | |
④ | 3883 | 2120 | 3322 | |
5# | ① | 2413 | 1502 | 1932 |
② | 2920 | 1586 | 2252 | |
③ | 3470 | 1708 | 3584 | |
④ | 3865 | 1944 | 3362 |
*本研究的数据采集得到国家自然科学基金委员会共享航次计划(航次编号: NORC-2012-08、NORC-2014-08)的资助, 该航次由中国科学院南海海洋研究所“实验2”号科考船实施, 在此一并致谢。
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