Petrography and geochemistry of impactites and volcanic bedrock in the ICDP drill core D1c from Lake El'gygytgyn, NE Russia
Petrography and geochemistry of impactites and volcanic bedrock in the ICDP drill core D1c from Lake El'gygytgyn, NE Russia
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俄罗斯东北部 Elgygytgyn 湖 ICDP 钻芯 D1c 中冲击岩和火山基岩的岩相学和地球化学
DOI：
10.1111/maps.12087
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发表时间：
2013
影响因子：
2.2
通讯作者：
Reimold
中科院分区：
文献类型：
--
作者：
Raschke;Schmitt;Reimold
位于西伯利亚东北部的3.6 Ma古老、直径18公里的El‘gytgyn撞击构造是由ICDP(国际大陆科学钻探计划)于2008/09年度钻探的。在中央隆起构造的外侧钻了一个517米长的岩心孔(D1c)，整体岩心采收率约为63%。从而，回收了约315米的湖泊沉积物和约202米的撞击物。在这里，我们提供了一个详细的岩石学和地球化学评价的影响角砾岩和基岩剖面在这个核心。97米长的下部基岩单元(湖底以下517-420米)由一块褐辉橄榄岩组成。在上覆基岩单元(420-390 Mblf)中，岩芯发现了一系列类似的火成岩和几个分米的镁铁质岩石。我们将这些单元解释为靠近其原来的撞击前位置的岩石，但由于中央隆起的坍塌而发生了一定程度的旋转(即，它代表了稀有的原地基底)。从大约390到328年，mblf以冲击熔体贫乏、碎屑为主的基质和岩屑和矿物碎屑出现，覆盖了El‘gytgyn地区已知的整个火山目的岩范围。在碎屑岩、基质的微碎屑岩和不同深度的闪锌矿中，观察到了冲击变质作用的所有阶段(未受冲击到熔融)。在这个包的正下方，在与下面的基岩的接触处，在玻璃斑状褐辉岩内出现了一条1米宽的剪切带，我们认为这是实际的火山口底部。最上层约12米，从328-316米深，似乎由精加工的硫化物组成，由沉积物和硫化物的混合物组成，与主要的硫化物单元相比，具有更多和平均更强的冲击矿物。这包括玻璃小球和冲击熔体碎片的一小部分。在这一单元的顶部，湖泊沉积逐渐成为这一段的主要物质。我们假设，这个单元包含喷发出的羽流的后备成分，它与撞击后陨石坑湖泊的第一批沉积物混合在一起，可能还有一些岩石从陨石坑内壁滑落--类似于在博苏姆特维湖(加纳)发现的LB-5A井沉积物部分底部的薄层。
The 3.6 Ma old and 18 km diameter El'gygytgyn impact structure in NE Siberia was drilled in 2008/09 by ICDP (International Continental Scientific Drilling Program). A 517 m long core hole (D1c) was drilled into the outer flank of the central uplift structure, with an overall core recovery of approximately 63%. Thereby, approximately 315 m lake sediments and approximately 202 m impactites were recovered. Here, we present a detailed petrographic and geochemical assessment of the impact breccia and bedrock sections in this core. The 97 m longlower bedrockunit (517–420 m below lake floor [blf]) consists of an ignimbrite. In the overlyingupper bedrockunit (420–390 mblf), the core recovered a sequence of similar ignimbrite and several decimeters of mafic rocks. We interpret these units as rocks that are located close to their former, preimpact position, but have been somewhat rotated due to collapse of the central uplift (i.e., it representsparautochthonous basement). From about 390 to 328 mblf occurs asuevitepackage with an impact melt poor, clast‐dominated matrix, and lithic and mineral clasts that cover the entire range of volcanic target rocks known from the El'gygytgyn region. All stages of shock metamorphism (unshocked to melted) were observed in clasts, and in microclasts of the matrix, of suevite from different depths. Immediately below this package, at the contact to the underlying bedrock, occurs a 1 m wide sheared zone within vitrophyric ignimbrite, which we consider the actual crater floor. The uppermost approximately 12 m, from 328–316 mblf depth, seem to comprisereworked suevite, consisting of a mixture of sediments and suevite with more and, on average, stronger shocked minerals than found in the main suevite unit. This includes a small component of glassy spherules and impact melt fragments. Toward the top of this unit, lake sediments progressively become the dominant material in this section. We assume that this unit contains a fallback component from the ejecta plume that was mixed with the first sediments of the postimpact crater lake, and possibly some rocks that slumped off the inner crater wall—similar to a thin layer at the base of the sediment section of borehole LB‐5A recovered in Lake Bosumtwi (Ghana).
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俄罗斯 Elgygytgyn 撞击坑 ICDP 钻芯 D1c 的冲击岩和基岩部分的岩石地层学
影响因子：
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作者：
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2000
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DOI：
--
发表时间：
2009
期刊：
影响因子：
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作者：
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影响因子：
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