The Bosumtwi meteorite impact structure, Ghana: A magnetic model
The Bosumtwi meteorite impact structure, Ghana: A magnetic model
复制标题
加纳 Bosumtwi 陨石撞击结构：磁性模型
DOI：
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
S. Elo
中科院分区：
文献类型：
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作者：
J. Plado;L. Pesonen;C. Koeberl;S. Elo
摘要：提出了非洲加纳 Bosumtwi 陨石撞击结构的磁模型。这个直径约 10.5 公里的相对年轻（约 1.07 Ma）的结构暴露在早元古代 Birimian-Tarkwaian 岩石中。该结构的中心部分埋在撞击后的湖泊沉积物下，由于缺乏岩心，地球物理学是揭示其内部结构的唯一方法。为了研究湖下和湖外的结构，对整个结构进行了高分辨率、低海拔（∼70 m）机载地球物理勘测，其中包括总磁场、电磁数据和伽马辐射的测量。磁力数据显示湖岸外有一个直径约 12 公里的环形磁晕。湖的中北部揭示了一个中心负磁异常，其北部和南部有较小的正侧异常，这是浅纬度磁体的典型特征。湖东、西段存在少量较弱的负磁异常。它们与北部的隆起物一起似乎环绕着一个中央隆起物。我们的模型表明，该结构的磁异常可能是由一种或几种相对强的剩磁化冲击熔岩或富含熔体的铁钙石体产生的。
Abstract— A magnetic model is proposed for the Bosumtwi meteorite impact structure in Ghana, Africa. This relatively young (∼1.07 Ma) structure with a diameter of ∼10.5 km is exposed within early Proterozoic Birimian—Tarkwaian rocks. The central part of the structure is buried under postimpact lake sediments, and because of lack of drill cores, geophysics is the only way to reveal its internal structure. To study the structure below and beyond the lake, a high‐resolution, low altitude (∼70 m) airborne geophysical survey across the structure was conducted, which included measurements of the total magnetic field, electromagnetic data, and gamma radiation. The magnetic data show a circumferential magnetic halo outside the lakeshore, ∼12 km in diameter. The central‐north part of the lake reveals a central negative magnetic anomaly with smaller positive side‐anomalies north and south of it, which is typical for magnetized bodies at shallow latitudes. A few weaker negative magnetic anomalies exist in the eastern and western part of the lake. Together with the northern one, they seem to encircle a central uplift. Our model shows that the magnetic anomaly of the structure is presumably produced by one or several relatively strongly remanently magnetized impact‐melt rock or melt‐rich suevite bodies.