Tectonic Implications of Partial Melting in the Ruby Mountain-East Humboldt Metamorphic Core Complex, Northeastern Nevada

深部地壳的物理和化学成分不可能在现场进行检查。因此，地球的这一部分仍然是谜，尽管它在造山过程中对地球化学运输具有重要意义，例如在形成矿藏方面也是重要的。对深部地壳的研究只能通过对从很深的地方挖出的岩石进行检查，而这项研究的重点是对内华达州一个暴露很深的红宝石-东洪堡山脉山核的岩石进行这样的研究。暴露在这一山脉中的岩石是变质的，起源于地球表面，在落基山脉形成期间由于埋藏而受到较高的压力和温度。事实上，这些岩石在足够深的地方开始融化，这种融化导致岩石物理性质的重大变化，类似于观察到的冰块开始融化时的变化，并在压缩力的作用下开始快速移动。本研究要检验的假设是这种熔融(其产物可以在今天的岩石露头中观察到)在多大程度上促进了这些高级变质岩迅速隆升、折返和侵位到山脉的核心。许多这种部分熔融的地壳深部变质带暴露在山脉的核心，这项研究的结果将直接适用于这些其他地体，并可能对整个山脉的演化产生深远的影响。这项研究将使P.I.和他的研究生能够收集必要的数据，以检验以下假设：通过相关的流变学和应变率变化，内华达州红宝石山脉-东洪堡山脉的部分熔融，启动了变质下地壳岩石向中地壳的侵位，为变质核杂岩的形成奠定了基础。这项研究将采用主副矿物测温法(包括新的石英钛温压计的应用)、原位U/Th-Pb和Sm-ND年代学以及扩散模拟来约束变橄榄岩部分熔融的条件和时间。这项研究的独特之处在于，它不仅确定了简单的进退/峰期变质作用的绝对和相对时间，而且还确定了特定的部分熔融反应及其进展，以及它们与变质核杂岩的冷却和折返历史的关系。这项研究的结果将对现今可能正在经历深熔作用的活动造山带核心的下地壳条件产生影响。作为这项研究的一部分收集的样本和数据并入MetPetDB(美国国家科学基金会资助的变质地球化学数据库)，扩大现有的公共数据集，并作为新用户的榜样，展示了MetPetDB作为协作工具的使用。

The physical and chemical makeup of the deep crust is impossible to examine in situ. Thus, this part of the earth has remained enigmatic despite its significance for geochemical transport during episodes of mountain building as is important, for example, in the generation of ore deposits. Study of the deep crust can only be undertaken through examination of rocks that have been exhumed from great depths, and the focus of this research is to conduct such a study on rocks of a deeply exposed mountain core in Nevada, the Ruby-East Humboldt range. Rocks exposed in this range are metamorphic and, having originated at the Earth's surface, were subjected to elevated pressures and temperatures as a result of burial during the formation of the Rocky Mountains. In fact, these rocks were at sufficient depth that they began to melt and this melting caused major changes in the physical properties of the rock, similar to changes observed in a block of ice when it begins to melt and, subjected to forces of compression, begins to move rapidly. The hypothesis to be examined and tested in the present study is the degree to which this melting (the products of which can be observed in the present day rock outcroppings) contributed to the rapid upheaval, exhumation, and emplacement of these high-grade metamorphic rocks into the core of the mountain range. Many such partially-melted deep crustal metamorphic belts are exposed in the cores of mountain ranges, and the results of this study will be directly applicable to these other terranes, and may have profound implications for the evolution of mountain belts in general.Funding will allow the P.I. and his graduate student to gather the data necessary to test the hypothesis that partial melting in the Ruby Mountains-East Humboldt Range, Nevada, through related changes in rheology and strain rates, initiated emplacement of metamorphosed lower crustal rocks into the middle crust to set the stage for metamorphic core complex formation. This research will employ major and accessory mineral thermobarometry (including an application of the new Ti-in-quartz thermobarometer), in situ U/Th-Pb and Sm-Nd geochronology, and diffusion modeling to constrain the conditions and timing of partial melting of metapelitic rocks. What is unique about this study is that it will determine both the absolute and relative timing of not simply prograde/peak metamorphism, but of specific partial melting reactions, their progress, and how they relate to the cooling and exhumation history of a metamorphic core complex. Results of this study will have implications for present day lower crustal conditions in the cores of active orogenic belts that may be undergoing anatexis. Samples and data collected as part of this research, incorporated into MetPetDB (the NSF-funded database for metamorphic geochemistry), acting to broaden the existing public dataset and serve as an example to new users, demonstrating the use of MetPetDB as a tool for collaboration.