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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Emplacement and composition of steep-sided domes on Venus
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Emplacement and composition of steep-sided domes on Venus

机译：金星上陡峭的圆顶的位置和组成

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Steep-sided domes on Venus have surface characteristics that can provide information on their emplacement, including relatively smooth upper surfaces, radial and polygonal fracture patterns, and pits. These characteristics indicate that domes have surface crusts which are relatively unbroken, have mobile interiors after emplacement, and preserve fractures from only late in their history in response to endogenous growth or sagging of the dome surface. We have calculated the time necessary to form a 12-cm-thick crust for basalt and rhyolite under current terrestrial and Venusian ambient conditions. A 12-cm-thick crust will form in all cases in < 10 hours. Although Venusian lava flows should develop a brittle carapace during emplacement, only late-stage brittle fractures are preserved at steep-sided domes. We favor an emplacement model where early-formed surface crusts are entrained or continually annealed as they deform to accommodate dome growth. Entrainment and annealing of fractures are not mutually exclusive processes and thus may both be at work during steep-sided dome emplacement. Our results are most consistent with basaltic compositions, as rhyolitic lavas would quickly form thick crusts which would break into large blocks that would be difficult to entrain or anneal. However, if Venus has undergone large temperature excursions in the past (producing ambient conditions of 800-1000 K [e.g., Bullock and Grinspoon, 1996, 1998]), rhyolitic lavas would be unable to form crusts at high surface temperatures and could produce domes with surface characteristics consistent with those of Venusian steep-sided domes. [References: 100]
机译：金星上陡峭的圆顶具有表面特征，可以提供有关其位置的信息，包括相对光滑的上表面，径向和多边形的裂缝模式以及凹坑。这些特征表明，穹顶具有相对完整的表皮，放置后具有可移动的内部空间，并且由于穹顶表面的内生生长或下垂而仅在裂缝的历史后期保留裂缝。我们已经计算了在当前陆地和金星环境条件下，形成玄武岩和流纹岩厚12厘米的硬皮所需的时间。在所有情况下，少于10小时就会形成12厘米厚的硬皮。尽管维纳斯熔岩流在安置过程中会形成脆性的甲壳，但在陡峭的圆顶上只能保留后期的脆性裂缝。我们主张采用一种放置模型，在该模型中，早期形成的地壳会变形或变形，以适应穹顶的生长而被夹带或持续退火。裂缝的夹带和退火不是相互排斥的过程，因此在陡峭的圆顶安装过程中都可能同时起作用。我们的结果与玄武岩成分最为吻合，因为流纹岩熔岩会迅速形成厚皮，将其破碎成大块，难以夹带或退火。但是，如果金星在过去经历过较大的温度偏移（产生800-1000 K的环境条件[例如Bullock和Grinspoon，1996年，1998年]），流纹岩熔岩将无法在高地表温度下形成结壳，并可能产生圆顶其表面特征与维纳斯陡峭圆顶的特征一致。 [参考：100]

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