摘要
南海西北部新生代以来发育了丰富的岩浆活动,记录了南海构造演化及其深部动力学过程的重要信息,然而南海西北部西沙岛礁区新生代岩浆岩地球物理特征研究相对薄弱。本研究通过地震剖面分析,结合前人地质和地球物理研究成果,识别了西沙岛礁区新生代岩浆岩反射特征和形态,圈定了研究区及其邻区新生代岩浆岩的分布范围并划分了期次,探讨了该地区新生代岩浆岩的形成机制。研究发现,西沙岛礁区发育了大量的新生代岩浆岩,以圆锥形的火山和岩浆侵入体为主,同时发育了丰富的以层状和碗状形态存在的火成岩席;相比于岛礁区东部,新生代岩浆岩在岛礁区西部及其外缘部分布较广,并受控于基底断裂的展布。根据地层与岩浆岩的接触关系,本研究将西沙岛礁区及其周缘的新生代岩浆活动划分为5个时期,包括裂陷期(23 Ma之前)、裂后期Ⅰ期(23~16 Ma)、裂后期Ⅱ期(16~5.5 Ma)、裂后期Ⅲ期(5.5~2.6 Ma)和裂后期Ⅳ期(2.6 Ma之后)。其中裂陷期岩浆活动十分薄弱,可能源自于裂陷期软流圈地幔减压熔融;而裂后期Ⅲ期和Ⅳ期岩浆活动极为强烈,这可能与哀牢山-红河断裂带及其向海延伸在5.5 Ma时期发生走滑反转和裂后期深部地幔岩浆物质上涌的综合作用有关。
Magmatic activities are well developed in the northwestern South China Sea since the Cenozoic,which record important information on the tectonic evolution of the South China Sea and its deep dynamic processes.However,the studies of geophysical characteristics of the Cenozoic igneous rocks in the Xisha Islands of the northwestern South China Sea are still poor.Through analyzing seismic profiles and previous geological and geophysical results,we identified the seismic reflection characteristics and geometries of the igneous rocks,specified their distribution and active periods,and discussed their formation mechanisms.Results show that a large number of Cenozoic igneous rocks have developed in the Xisha Islands.These rocks are primarily consists of conical volcanoes and magmatic intrusives as well as abundant igneous sills,layered or bowl-shaped,and are more widely distributed in the western part and its outer edges of the islands region than those in the eastern part,along mostly the basement faults.According to the contact relationships between strata and igneous rocks,the Cenozoic igneous activities in the study region could be divided into five periods,i.e.,the syn-rift period(before 23 Ma),post-rift periodⅠ(23~16 Ma),post-rift periodⅡ(16~5.3 Ma),post-rift periodⅢ(5.3~2.6 Ma),and post-rift periodⅣ(after 2.6 Ma).The magmatism in the syn-rift period was very weak and probably derived from the decompression melting of the asthenosphere during the rifting,while in the post-riftⅢandⅣperiods were very intensive.We proposed that the significant igneous activities since the Pliocene in the Xisha region was probably cause by the interaction of the strike-slip reversal of the Ailao Shan-Red River fault zone and its seaward extension into the sea at ca.5.5 Ma and the deep mantle upwelling during the post-rift period.
作者
周金扬
邢磊
董冬冬
高金尉
ZHOU Jinyang;XING Lei;DONG Dongdong;GAO Jinwei(College of Marine Geosciences,Ocean University of China,Qingdao 266100,China;Lusheng Oil Production Company,Shengli Oilfield,Dongying 257000,China;Key Laboratory of Marine Geophysical Prospecting Technology of Qingdao,Qingdao 266100,China;National Engineering Research Center of Offshore Oil and Gas Exploration,Beijing 100029,China;Key Laboratory of Marine Geology and Environment,Institute of Oceanology,Chinese Academy of Sciences,Qingdao 266071,China;Laboratory of Marine Geophysics and Georesources,Institute of Deep-Sea Science and Engineering,Chinese Academy of Sciences,Sanya 572000,China)
出处
《海洋地质与第四纪地质》
北大核心
2025年第5期115-127,共13页
Marine Geology & Quaternary Geology
基金
青岛新能源山东省实验室项目“基于四维地震技术的海洋碳封存及提高原油采收率研究”(QNESL OP202304)
海南省重点研发计划科技合作方向(国际科技合作研发)项目“南海西沙海域新生代岩浆岩及其CO_(2)封存潜力”(GHYF2022009)
国家自然科学基金“基于冷泉羽状流声学特征的甲烷通量研究——以‘F’站位为例”(42276055)
“南海西部陆缘构造活动时空特征及区域应力相互作用研究”(42276066)
山东省本科教学改革项目“新工科通识教育课程建设探索——以《在海洋中给地球做CT》为例”(M2023313)。
关键词
新生代岩浆活动
地震反射特征
软流圈地幔部分熔融
深部地幔上涌
西沙岛礁区
Cenozoic igneous activity
seismic reflection characteristics
partial melting of asthenosphere
deep mantle upwelling
Xisha Islands
