桑托斯盆地L构造Aptian期火山喷发旋回特征与Itapema组介壳灰岩沉积
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本文为国家科技重大专项“海外重点探区目标评价与未来领域选区选带研究”(编号2016ZX05029005)资助的成果。


Multiple pulses eruption of Aptian magma and their key role in the deposition of coquinas limestone in the Itapema Formation in Block L, Santos basin
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    摘要:

    桑托斯盆地裂陷初期岩浆活动与储层发育关系密切。本文以盆地L区块火成岩- 介壳灰岩复合体为研究对象,通过对火成岩岩石学、年代学测试及钻井、测井资料分析等,首次明确了桑托斯盆地裂陷初期岩浆活动特征及其对介壳灰岩沉积过程的控制,并指出介壳灰岩储层的分布特征。L区块内火成岩分属晚白垩世Santonian期—Campanian期和早白垩世Aptian两期岩浆活动产物,并以Aptian期为主,至少经历了7次不连续喷发和3次侵入过程,形成了块状玄武岩、杏仁状玄武岩和玻基斑状玄武岩(含再沉积玻基斑状玄武岩)等喷发相火成岩和以辉绿岩(局部属粗玄岩)、煌斑岩形式产出的侵入相火成岩。Aptian期岩浆多期活动重塑了古地貌,形成了局部构造凸起,促成并控制了下白垩统Itapema组至少6期介壳灰岩沉积,最终形成了~620 m厚火成岩- 介壳灰岩复合体。介壳灰岩储层呈透镜体形状,以“散点式”不连续分布在Aptian期盆内古隆、古断阶(坡)等区域,横向连续性差,垂向连通性受限,其发育规模和质量受古地貌及水深条件等影响。

    Abstract:

    Magma events in the early stage of basin rifting in the Santos basin played a key role in the development of the carbonate reservoir. Taking the igneous rock- coquinas complex in Block L as a case study, this paper revealed two stages of magma events through systemic analysis, testing of igneous rock mineralogy, petrology, geochronology, petro- geochemistry, and wireline log curves. Compared with Santonian- Campanian thin layers of intrusive bodies, the Aptian extrusive magma dominated this complex and experienced at least 11 episodes of eruptions, including 7 discontinuous eruptions and 3 continuous multi- pulse eruptions, forming three main types of eruptive facies igneous rocks, including massive basalts, amygdaloidal basalts, and hyaloclastite. At the same time, this eruption process was also accompanied by 3 intrusions processes, in the form of diabase and lamprophyre. The multiple- phase of Aptian magma, as a key geological element, built up a paleo- high in place which contributed to, and controlled, the deposition of at least 6 stages of coquinas limestone in the ITP Fm.Finally, anigneous rock- coquinas limestone complex with a height of more than 620 meters was formed. Correspondingly, coquinas reservoirs developed as lens shapes, distributed in “dispersed spots” patterns, with low extension scale and limited vertical connectivity. The distribution scale and coquinas limestone quality was strongly affected by paleogeomorphology and water depth.Suitable paleogeomorphology determines their lateral distribution, while water depth variation determines their vertical thickness and depositioncycles.The multiple pulse eruption of Aptian magma and cumulatively increased igneous rock thickness not only created paleogeomorphology, but also caused relative changes of water depth.This is the first study to clarify the characteristics of magma events inthe basin's early rifting stage, its control on the depositional process of coquinas limestone, and finally point out the possible distribution of coquinas reservoirs in the Santos basin.

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赵健,赵俊峰,任康绪,王红平,王朝锋,阳孝法,杨柳.2023.桑托斯盆地L构造Aptian期火山喷发旋回特征与Itapema组介壳灰岩沉积[J].地质学报,97(2):539-552.
Zhao Jian, Zhao Junfeng, Ren Kangxu, Wang Hongping, Wang Chaofeng, Yang Xiaofa, Yang Liu.2023. Multiple pulses eruption of Aptian magma and their key role in the deposition of coquinas limestone in the Itapema Formation in Block L, Santos basin[J]. Acta Geologica Sinica,97(2):539-552.

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  • 收稿日期:2021-05-09
  • 最后修改日期:2021-09-14
  • 录用日期:2021-09-15
  • 在线发布日期: 2023-03-03