Fluid-present melting of the deep crust: implications for the tectonics of large convergent orogens

深部地壳的流体熔融：对大型聚合造山带构造的影响

• 批准号: RGPIN-2015-04040
• 负责人: Yakymchuk, Christopher
• 金额: $ 1.75万
• 依托单位: University of Waterloo
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=669128
• 关键词: Fluid; present; melting; deep; crust

The interaction of fluids with rocks in the deep continental crust plays a critical role in the redistribution of mass and energy during the buildup and collapse of mountain belts and the genesis of ore deposits. During the construction of large mountain belts, crustal thickening generates elevated temperatures and pressures in the deep crust. Widespread fluid influx into the deep hot crust beneath mountain belts promotes partial melting, which drastically weakens large regions of continental crust. These melt-weakened regions may act as large-scale shear zones that facilitate mountain buildup or may flow laterally towards orogenic fronts resulting in the formation of high-elevation plateaux. For example, geophysical imaging suggests that large regions of partially molten crust are present beneath the Himalayan mountain belt and the lateral movement of this melt-weakened material is proposed to play a first-order role in the development of the Tibetan Plateau. While widespread fluid-fluxed partial melting may have important tectonic consequences, the sources, compositions and transport pathways of these fluids are poorly constrained. This is due, in part, to the lack of access to the deep crust beneath modern mountain belts.*** The Grenville Province of southwestern Ontario represents the deeply eroded core of an ancient Himalayan-scale mountain belt. This region represents a natural laboratory to investigate the processes that are occurring beneath modern mountain belts - such as the Himalaya in Asia and the Andes in South America. This research program will investigate the role of fluid infiltration and partial melting on the tectonic evolution of an ancient mountain belt using both geological field mapping and geochemical laboratory work. Fieldwork will constrain the transport pathways for fluids in the deep crust exposed in Ontario. Laboratory work will evaluate the source and compositions of the fluids as well as the timing of fluid infiltration using modern geochemical techniques at the University of Waterloo. The results of this research program will provide insights into the role of fluid infiltration in the deep crust on the tectonic evolution of modern and ancient mountain belts. *** Fluids play an important role in scavenging elements of economic interest (e.g. gold, uranium, and tin) from the deep crust and transporting them to the shallower crust where they generate mineral deposits. However, our understanding of fluid-rock interaction in the deep crust is still rudimentary. Therefore, a broader implication of this research program is an improved understanding of fluid-rock interaction beneath modern and ancient mountain belts, which can be used to improve genetic models of metalliferous ore deposits and to prioritize exploration for these deposits in Canada and around the world.**

在深层大陆地壳中，液体与岩石与岩石的相互作用在山带的积聚和崩溃和矿石沉积物的结构期间的质量和能量重新分布中起着关键作用。在建造大山皮带期间，地壳增厚会产生较高的地壳中的温度和压力。山皮带下方的深层壳中广泛涌入的液体会促进部分熔化，从而大大削弱了大陆壳的大区域。这些融化的区域可能充当大规模的剪切区，促进山区的积聚，或者可能侧向流向造山阵线，从而形成高升高的高原。例如，地球物理成像表明，在喜马拉雅山带下方存在部分熔融地壳的大区域，并且提出这种熔融垂直材料的横向运动在藏族高原的发展中起一阶作用。虽然普遍的流体液液部分熔化可能会带来重要的构造后果，但这些流体的来源，组成和运输途径受到限制不佳。这部分是由于无法进入现代山带下方的深层地壳。该地区代表了一个自然实验室，以调查现代山带下发生的过程 - 例如亚洲的喜马拉雅山脉和南美的安第斯山脉。该研究计划将使用地质田地映射和地球化学实验室工作研究流体浸润和部分融化对古老山带构造演变的作用。现场工作将限制安大略省在深层外壳中流体的运输途径。实验室工作将评估流体的来源和组成以及使用滑铁卢大学现代地球化学技术的流体渗透时间。该研究计划的结果将提供有关流体浸润在现代和古老山带构造进化中的作用的见解。 ***液体在清除经济利益的要素（例如黄金，铀和锡）中起着重要作用，并将它们运送到产生矿物质矿床的浅层壳中。但是，我们对深层地壳中流体岩石相互作用的理解仍然是基本的。因此，该研究计划的更广泛的含义是对现代和古老山带下面的流体岩石相互作用的了解，可用于改善金属矿床的遗传模型，并优先考虑加拿大和世界各地这些沉积物的探索。**************