Core‐Log‐Seismic Integration in Metamorphic Rocks and Its Implication for the Regional Geology: A Case Study for the ICDP Drilling Project COSC‐1, Sweden
Core‐Log‐Seismic Integration in Metamorphic Rocks and Its Implication for the Regional Geology: A Case Study for the ICDP Drilling Project COSC‐1, Sweden
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DOI：
10.1029/2020gc009376
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发表时间：
2021-01
期刊：
影响因子：
3.7
通讯作者：
J. Elger;C. Berndt;Felix Kästner;S. Pierdominici;J. Kück;B. Almqvist;C. Juhlin;H. Lorenz
中科院分区：
文献类型：
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作者：
J. Elger;C. Berndt;Felix Kästner;S. Pierdominici;J. Kück;B. Almqvist;C. Juhlin;H. Lorenz
大陆碰撞导致地壳沿剪切带变形。然而，这些带的物理和化学条件以及使构造运移能够长达数百公里的变形过程仍然不清楚，因为它们发生的深度和成像方面的挑战。古老的碰撞带使我们能够更好地研究这些过程，例如在斯堪的纳维亚喀里多尼迪斯中部的COSC-1钻孔。这项研究将COSC-1井的数据与不同的地震测量相结合，以提供对塞夫推覆杂岩的空间、岩性和结构形态的约束。这是为数不多的表明变质岩中岩心-测井-地震综合能够识别主要岩性单位的空间分布的研究之一。尤其是伽马测井结合密度资料是在测井-岩心对比中区分镁铁质和长英质岩性的有力工具。我们的结果表明，沿钻孔的反射主要是由成分变化而不是结构变化引起的。塞夫推覆杂岩中的反射不像在更深的地方那样明显，但是连续的，其中几个可能与变质叠加的岩浆侵入有关。它们的背景表明，塞夫推覆杂岩由火山大陆边缘的残留物组成。我们的结果表明，韧性变形的中地壳反射率主要是造山前岩性变化的函数，在解释造山过程时必须考虑这一点。
Continental collision causes deformation in the crust along shear zones. However, the physical and chemical conditions at which these zones operate and the deformation processes that enable up to hundreds of km of tectonic transport are still unclear because of the depth at which they occur and the challenges in imaging them. Ancient exhumed collision zones allow us to investigate these processes much better, for example at the COSC‐1 borehole in the central Scandinavian Caledonides. This study combines data from the COSC‐1 borehole with different seismic measurements to provide constraints on the spatial lithological and textural configuration of the Seve Nappe Complex. This is one of the few studies that shows that core‐log‐seismic integration in metamorphic rocks allows to identify the spatial distribution of major lithological units. Especially gamma ray logs in combination with density data are powerful tools to distinguish between mafic and felsic lithologies in log‐core correlation. Our results indicate that reflections along the borehole are primarily caused by compositional rather than textural changes. Reflections in the Seve Nappe Complex are not as distinct as in greater depths but continuous and several of them can be linked to magmatic intrusions, which have been metamorphically overprinted. Their setting indicates that the Seve Nappe Complex consists of the remnants of a volcanic continental margin. Our results suggest that ductile‐deformed middle crustal reflectivity is primarily a function of pre‐orogenic lithological variations which has to be considered when deciphering mountain building processes.