Exploring the roles of sediment provenance and igneous activity on the development of synrift lacustrine source rocks, Pearl River Mouth Basin, northern South China Sea
Exploring the roles of sediment provenance and igneous activity on the development of synrift lacustrine source rocks, Pearl River Mouth Basin, northern South China Sea
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DOI：
10.1016/j.marpetgeo.2022.105990
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发表时间：
2022-11-07
影响因子：
4.2
通讯作者：
Bidgoli，Tandis
中科院分区：
文献类型：
--
作者：
Wang，Wei;Zeng，Zhiwei;Bidgoli，Tandis
珠江口盆地文昌组和恩平组的湖相泥岩是珠江口盆地的主要烃源岩，其烃源岩的丰度和质量各不相同。虽然已知有机生产力在这些岩石的发育中发挥了作用，但在以前的研究中大多被忽视。在这项研究中，新的锆石地质年代学数据从火成岩侵入岩和火山岩钻孔的PRMB一起编译碎屑锆石U-Pb年龄从古近系砂岩破译沉积物源区和火山活动的作用，在源岩的发展。结果表明，文昌组（49-39 Ma）沉积时，沉积物主要来自以燕山期火成岩为主的盆内构造高点（180-90 Ma）。文昌组火山岩和碎屑岩在年轻时代（42-45 Ma）的相似性表明火山活动与沉积同时发生。近源区的化学风化作用与火山物质共同为盆地提供了丰富的营养物质，提高了原生有机质生产力，形成了以浮游生物为主的优质湖相烃源岩。恩平组（39-33 Ma）碎屑锆石的物源表明，沉积物来自华南地块，其岩性复杂，锆石年龄较大。SCB沉积物的长距离运输稀释了较大和较浅湖泊的生产性营养条件，并引入了来自高等陆生植物的有机质。该研究为湖相烃源岩的评价提供了一种新的方法，特别是对于泥岩样品有限的深水地区。
Lacustrine mudstones developed in the synrift Wenchang and Enping formations are the major source rocks of the Pearl River Mouth Basin (PRMB) and vary in both richness and quality of hydrocarbons generated. While organic productivity is known to have played a role in the development of these rocks, it has been mostly neglected in prior research. In this study, new zircon geochronological data from igneous intrusive and volcanic rocks in boreholes of the PRMB are used alongside compiled detrital zircon U-Pb ages from Paleogene sandstones to decipher the roles of sediment provenance and volcanic activity in the development of source rocks. The result suggests that during deposition of the Wenchang Formation (49-39 Ma), sediments were mainly derived from intrabasinal structural highs dominated by Yanshanian igneous rocks (180-90 Ma). Similarities in young ages (42–45 Ma) in volcanic and clastic units of the Wenchang Formation suggest volcanic activity concurrent with its deposition. Chemical weathering of the proximal source area together with volcanic materials provided abundant nutrients for the basin and enhanced the primary organic productivity, resulting in the development of high-quality lacustrine source rocks, derived mainly from plankton. In contrast, the detrital zircon provenance of the Enping Formation (39-33 Ma) suggests sediments were derived from the South China Block (SCB), far to the north, with complicated lithologies and more older zircon grains. The long-distance transport of SCB sediments diluted the productive nutrition conditions of the larger and shallower lakes, and introduced organic matter derived from higher terrestrial plants. This study provides a new approach to evaluating the lacustrine source rocks especially for the deep-water areas with limited mudstone samples.