Magmatic underplating, plumbing system, and carbon-enhanced electrical conductivity in the Paraná Magmatic Province

IF 2.4 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
Gabriel Negrucci Dragone, Mauricio de Souza Bologna
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引用次数: 0

Abstract

The origin of large igneous provinces (LIPs) is still an enigma but likely involves magma storage and pathways spread throughout the crust, requiring indirect methods for its study. Here, we present 3-D resistivity models derived from the inversion of broadband (∼0.0001–3000 s) magnetotelluric data with 9–13 km lateral spacing in the central Paraná Magmatic Province, an expressive Early Cretaceous LIP in South America. Our results map in greater detail the previously interpreted LIP magma conduit and support, in contrast with seismological models, significant magmatic underplating to explain the observed conductivity near the LIP central axis. The potential axial lava feeder appears as a pair of crustal conductors (5–15 km; >0.1 S/m) parallel to the region of maximum thickness of both pre-volcanic sedimentary rocks and erupted tholeiitic basalts along an extension of at least 800 km. We propose the high conductivity is due to graphite films of precipitated carbon during the ascension of carbon-bearing fluids released by crystallizing magmas underplated at the base of the crust. The association of high conductivity with underplating is supported by high Vp/Vs ratios close to the conductive lineament, by a lower-crustal zone of high P-wave velocities at the basin axis attributed to mafic intrusions, and by a residual gravity high interpreted as gabbros underplated/intruded in the lower crust. Moreover, the conductive lineament is spatially associated with intracrustal high densities inferred from geoid inversion and upper-crustal high P-wave velocities. Early CO2 release during crystallization of underplated magma before eruption could explain the time gap between the Weissert ocean anoxic event and the volcanism. Our study advances in the controversial topic of magmatic intrusive components in the Paraná LIP with implications for LIP generation and paleo-climate studies.

Abstract Image

巴拉那岩浆省的岩浆底板、管道系统和碳增强导电性
大型火成岩带(LIPs)的起源仍然是一个谜,但很可能涉及岩浆的储存和遍布整个地壳的途径,因此需要采用间接的方法对其进行研究。在这里,我们展示了通过反演南美洲巴拉那岩浆省(Paraná Magmatic Province)中部横向间距为 9-13 千米的宽带(0.0001 ∼ 3000 秒)磁电uric 数据而得出的三维电阻率模型,巴拉那岩浆省是南美洲一个具有表现力的早白垩世 LIP。我们的研究结果更详细地描绘了之前解释的 LIP 岩浆导管,并与地震学模型相反,支持用显著的岩浆下沉来解释在 LIP 中轴附近观测到的传导性。潜在的轴向熔岩馈源表现为一对地壳导体(5-15 km; >0.1S/m),与火山前沉积岩和喷发的透辉玄武岩厚度最大的区域平行,延伸至少 800 km。我们认为,高电导率是由于结晶岩浆在地壳底部沉积时释放的含碳流体上升过程中沉淀的碳石墨膜造成的。导电线附近的高Vp/Vs比值、盆地轴线处因岩浆侵入而形成的高P波速度的下地壳区,以及被解释为下地壳岩浆侵入的辉长岩的残余重力高点,都证明了高导电率与下地壳的联系。此外,导电线与根据大地水准面反演和上地壳高P波速度推断出的地壳内高密度在空间上有关联。在火山爆发之前,火山岩浆在结晶过程中释放出的早期二氧化碳可以解释魏塞特海洋缺氧事件与火山活动之间的时间差。我们的研究推动了巴拉那LIP中岩浆侵入成分这一争议性课题的研究,并对LIP的生成和古气候研究产生了影响。
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来源期刊
Physics of the Earth and Planetary Interiors
Physics of the Earth and Planetary Interiors 地学天文-地球化学与地球物理
CiteScore
5.00
自引率
4.30%
发文量
78
审稿时长
18.5 weeks
期刊介绍: Launched in 1968 to fill the need for an international journal in the field of planetary physics, geodesy and geophysics, Physics of the Earth and Planetary Interiors has now grown to become important reading matter for all geophysicists. It is the only journal to be entirely devoted to the physical and chemical processes of planetary interiors. Original research papers, review articles, short communications and book reviews are all published on a regular basis; and from time to time special issues of the journal are devoted to the publication of the proceedings of symposia and congresses which the editors feel will be of particular interest to the reader.
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