Collaborative Research: Testing for Rapid Pulses of Crustal-scale Heat and Mass Transfer by Fluids in Metamorphic "Hot Spots", New Hampshire, USA

合作研究：测试美国新罕布什尔州变质“热点”中流体的地壳尺度传热传质快速脉冲

• 批准号: 0948102
• 负责人: C. Page Chamberlain
• 金额: $ 8.84万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-08-01 至 2014-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0948102&HistoricalAwards=false
• 关键词: Collaborative; Research; Testing; Rapid; Pulses

Intellectual Merit. This project addresses the role of H-O-C fluids in heat transfer associated with formation of a Paleozoic belt of metamorphic 'hot spots' exposed in a north-south transect across New Hampshire (NH). At each of these localities, steep gradients in metamorphic temperature and rock geochemistry are centered on syn-metamorphic quartz±graphite vein networks. Chamberlain and Rumble (1988) proposed the hypothesis that these features represent zones where large quantities of hot fluids ascended through fracture networks during Acadian regional metamorphism. On the other hand, numerical modeling studies have shown that typical regional metamorphic devolatilization is unlikely to transport sufficient heat to strongly perturb regional geotherms. It would appear that hot spots can only be produced if the fluid fluxes are enormous and the timescales of flow are extremely short, but it is unknown if such fluxes and timescales are realistic. A multidisciplinary approach is proposed to test this hypothesis. Field work will focus on well-exposed hot spot localities near Bristol and Nelson, NH. The hypothesis must pass five crucial tests. (1) Fluid fluxes must have been large. Time-integrated fluid fluxes through veins will be estimated by quantifying chemical and isotopic (O, H) mass transfer in the vein networks. (2) Fluid flow must have been in a direction of decreasing temperature. The nature and extent of chemical and isotopic metasomatism will determine the direction of fluid flow, and elucidate fluid sources and pathways. (3) Timescales of flow must have been short (10^6 yrs). The absolute timing of hot spot formation will be determined using Sm/Nd dating of garnet in metamorphic rocks, and U/Pb dating of monazite and zircons in metamorphic rocks and any magmatic dikes in the field areas. Furthermore, chemical diffusion profiles in calcite, apatite, and garnet will be used to constrain timescales of peak heating. (4) The timing of peak thermal conditions must have been nearly synchronous across isograds (test via Sm/Nd and U/Pb dating). (5) Metamorphic pressures must have been roughly constant across isograds at the present level of exposure. Thermobarometry will be done to determine peak conditions, regional T/P gradients, and P-T-t paths. Knowledge of the time-integrated fluid fluxes and timescales of flow will allow estimation of the actual fluid fluxes through the hot spots as well as gradients in the fluxes across the field areas. This information, together with the P-T-t history, age(s) of fluid flow, and field relations, will provide the initial and boundary conditions needed for modeling of fluid flow (2-dimensional) and its effect on regional thermal structure. If the hypothesis fails then other alternatives will be investigated, including magmatism and upwelling of lower crustal gneiss domes. The Ague lab will take primary responsibility for thermobarometry, mass transfer analysis, and diffusion and flow modeling; the Baxter lab for Sm/Nd garnet dating; and the Chamberlain lab for stable isotope and U/Pb work. Broader Impacts. Large fluid fluxes poentially transport mass as well as heat. Therefore, if correct, the hypothesis of fluid-driven heating would bear on problems of societal relevance including ore metal transport and the transfer of greenhouse gases out of metamorphic belts. Human resources will be developed because Ph.D. graduate student and undergraduate involvement is critical. PIs and students will take part in field work and, in Years 2 and 3, coordinate "group meetings" at international conferences. All of the PIs have advised women students and are committed to diversity, including the involvement of underrepresented minority groups in science. Ague spearheaded development of the new Hall of Minerals, Earth, and Space (HoMES) at the Yale Peabody Museum, allowing integration of new research results into Earth science displays viewed by over 150,000 visitors annually. A large fraction of these visitors are schoolchildren, many of whom live in the urban centers of New Haven, Bridgeport, and other Connecticut cities. Moreover, Ague has separate NSF funding to develop educational programs based on the new Hall for area schoolteachers. Baxter will incorporate the field area into his annual "RoBOT: Rocks Beneath Our Toes" outreach program as a part of his Fall mineralogy class. The program engages Boston area high school students and BU undergraduates.

智力优点。该项目介绍了H-O-C流体在与形成在新罕布什尔州（NH）的南北样品中暴露的变质“热点”的传热相关的传热中的作用。在这些地方的每个地方，变质温度和岩石地球化学中的钢梯度都集中在Syn-Metamorphic Quartz±图形静脉网络上。 Chamberlain and Rumble（1988）提出了这样一个假设，即这些特征代表了阿卡迪亚区域变质过程中通过断裂网络上升的大量热通量。另一方面，数值建模研究表明，典型的区域变质性脱脂化不太可能将足够的热量运输到强烈扰动区域地热的热量。似乎只有当流体通量巨大而流动的时间尺度非常短，但是尚不清楚此类通量和时间尺度是否现实，才能产生热点。提出了一种多学科方法来检验这一假设。现场工作将集中在新罕布什尔州布里斯托尔和纳尔逊附近的曝光热点地区。该假设必须通过五项关键检验。 （1）流体通量必须很大。通过量化静脉网络中的化学和同位素（O，H）传质，可以估算通过静脉的时间整合流体通量。 （2）流体流量必须朝着降低温度的方向。化学和同位素化学的性质和程度将决定流体流动的方向，并阐明流体源和途径。 （3）流动的时间尺度必须很短（10^6年）。热点形成的绝对时机将使用变质岩石中石榴石的SM/ND定期确定，以及在变质岩石中的单唑和锆石的U/PB日期以及田间区域中的任何岩浆堤防。此外，钙，磷灰石和石榴石中的化学扩散谱将用于限制峰加热的时间尺度。 （4）峰值热条件的时机必须在异义压之间几乎是同步的（通过SM/ND和U/PB测试测试）。 （5）在暴露介绍水平上，跨同层的变质压力必须大致恒定。将进行热压测定法以确定峰值条件，区域T/P梯度和P-T-T路径。了解时间集成的流体通量和流量的时间尺度将允许估计通过热点的实际流体通量以及整个场区域通量的梯度。这些信息以及P-T-T历史，流体流量的年龄以及场关系，将提供对流体流动（2维）建模（二维）及其对区域热结构的影响所需的初始和边界条件。如果假设失败，则将研究其他替代方案，包括岩浆和下层地壳片麻岩植物的上升。 Ague Lab将对热压法，传质分析以及扩散和流程建模承担主要责任。用于SM/ND石榴石约会的巴克斯特实验室；以及用于稳定同位素和U/PB工作的Chamberlain实验室。更广泛的影响。大型流体通量主要是转运质量和热量。因此，如果正确的话，流体驱动的加热的假设将存在社会相关性问题，包括矿石金属运输以及从变质带中的温室气体转移。人力资源将是因为博士学位而开发的。研究生和本科参与至关重要。 PIS和学生将参加现场工作，并在第2年和第3年参加国际会议协调“小组会议”。所有PI都为女学生提供了建议，并致力于多样性，包括参与不足的少数群体参与科学。 Ague率领耶鲁Peabody博物馆的新矿物，地球和空间（房屋）的新大厅的发展，允许将新的研究结果整合到每年15万名游客观看的地球科学展示中。这些游客中有很大一部分是学童，其中许多人居住在纽黑文，布里奇波特和其他康涅狄格州城市的城市中心。此外，Ague拥有单独的NSF资金，可以根据新的学校教师的新礼堂制定教育计划。巴克斯特（Baxter）将把现场区域纳入他的年度“机器人：脚趾下方”外展计划的岩石，作为他秋季Mineraology课程的一部分。该计划与波士顿地区的高中生和BU大学生有关。