Madison East

Bio: Madison East is an academic researcher from University of Sydney. The author has contributed to research in topics: Lithosphere & Outgassing. The author has an hindex of 2, co-authored 3 publications receiving 38 citations.

Deep carbon cycling over the past 200 million years: a review of fluxes in different tectonic settings

Abstract: Carbon is a key control on the surface chemistry and climate of Earth. Significant volumes of carbon are input to the oceans and atmosphere from deep Earth in the form of degassed CO2 and are returned to large carbon reservoirs in the mantle via subduction or burial. Different tectonic settings (e.g., volcanic arcs, mid-ocean ridges, and continental rifts) emit fluxes of CO2 that are temporally and spatially variable, and together they represent a first-order control on carbon outgassing from the deep Earth. A change in the relative importance of different tectonic settings throughout Earth’s history has therefore played a key role in balancing the deep carbon cycle on geological timescales. Over the past 10 years the Deep Carbon Observatory has made enormous progress in constraining estimates of carbon outgassing flux at different tectonic settings. Using plate boundary evolution modeling and our understanding of present-day carbon fluxes, we develop time series of carbon fluxes into and out of the Earth’s interior through the past 200 million years. We highlight the increasing importance of carbonate-intersecting subduction zones over time to carbon outgassing, and the possible dominance of carbon outgassing at continental rift zones, which leads to maxima in outgassing at 130 and 15 Ma. To a first-order, carbon outgassing since 200 Ma may be net positive, averaging ∼50 Mt C yr–1 more than the ingassing flux at subduction zones. Our net outgassing curve is poorly correlated with atmospheric CO2, implying that surface carbon cycling processes play a significant role in modulating carbon concentrations and/or there is a long-term crustal or lithospheric storage of carbon which modulates the outgassing flux. Our results highlight the large uncertainties that exist in reconstructing the corresponding in- and outgassing fluxes of carbon. Our synthesis summarizes our current understanding of fluxes at tectonic settings and their influence on atmospheric CO2, and provides a framework for future research into Earth’s deep carbon cycling, both today and in the past.

Plate Tectonics in the Late Paleozoic

Abstract: As the chronicle of plate motions through time, paleogeography is fundamental to our understanding of plate tectonics and its role in shaping the geology of the present-day. To properly appreciate the history of tectonics—and its influence on the deep Earth and climate—it is imperative to seek an accurate and global model of paleogeography. However, owing to the incessant loss of oceanic lithosphere through subduction, the paleogeographic reconstruction of ‘full-plates’ (including oceanic lithosphere) becomes increasingly challenging with age. Prior to 150 Ma ∼60% of the lithosphere is missing and reconstructions are developed without explicit regard for oceanic lithosphere or plate tectonic principles; in effect, reflecting the earlier mobilistic paradigm of continental drift. Although these ‘continental’ reconstructions have been immensely useful, the next-generation of mantle models requires global plate kinematic descriptions with full-plate reconstructions. Moreover, in disregarding (or only loosely applying) plate tectonic rules, continental reconstructions fail to take advantage of a wealth of additional information in the form of practical constraints. Following a series of new developments, both in geodynamic theory and analytical tools, it is now feasible to construct full-plate models that lend themselves to testing by the wider Earth-science community. Such a model is presented here for the late Paleozoic (410–250 Ma) together with a review of the underlying data. Although we expect this model to be particularly useful for numerical mantle modeling, we hope that it will also serve as a general framework for understanding late Paleozoic tectonics, one on which future improvements can be built and further tested.

Subduction Fluxes of Water, Carbon Dioxide, Chlorine, and Potassium

Abstract: [1] The alteration of upper oceanic crust entails growth of hydrous minerals and loss of macroporosity, with associated large-scale fluxes of H2O, CO2, Cl−, and K2O between seawater and crust. This age-dependent alteration can be quantified by combining a conceptual alteration model with observed age-dependent changes in crustal geophysical properties at DSDP/ODP sites, permitting estimation of crustal concentrations of H2O, CO2, Cl−, and K2O, given crustal age. Surprisingly, low-temperature alteration causes no net change in total water; pore water loss is nearly identical to bound water gain. Net change in total crustal K2O is also smaller than expected; the obvious low-temperature enrichment is partly offset by earlier high-temperature depletion, and most crustal K2O is primary rather than secondary. I calculate crustal concentrations of H2O, CO2, Cl−, and K2O for 41 modern subduction zones, thereby determining their modern mass fluxes both for individual subduction zones and globally. This data set is complemented by published flux determinations for subducting sediments at 26 of these subduction zones. Global mass fluxes among oceans, oceanic crust, continental crust, and mantle are calculated for H2O, Cl−, and K2O. Except for the present major imbalance between sedimentation and sediment subduction, most fluxes appear to be at or near steady state. I estimate that half to two thirds of subducted crustal water is later refluxed at the prism toe; most of the remaining water escapes at subarc depths, triggering partial melting. The flux of subducted volatiles, however, does not appear to correlate with either rate of arc magma generation or magnitude of interplate earthquakes.

Supporting Online Material for Major Australian-Antarctic Plate Reorganization at Hawaiian-Emperor Bend Time

Abstract: A marked bend in the Hawaiian-Emperor seamount chain supposedly resulted from a recent major reorganization of the plate-mantle system there 50 million years ago. Although alternative mantle-driven and plate-shifting hypotheses have been proposed, no contemporaneous circum-Pacific plate events have been identified. We report reconstructions for Australia and Antarctica that reveal a major plate reorganization between 50 and 53 million years ago. Revised Pacific Ocean sea-floor reconstructions suggest that subduction of the Pacific-Izanagi spreading ridge and subsequent Marianas/Tonga-Kermadec subduction initiation may have been the ultimate causes of these events. Thus, these plate reconstructions solve long-standing continental fit problems and improve constraints on the motion between East and West Antarctica and global plate circuit closure.

Mountains, erosion and the carbon cycle

Abstract: Mountain building results in high erosion rates and the interaction of rocks with the atmosphere, water and life. Carbon transfers that result from increased erosion could control the evolution of Earth’s long-term climate. For decades, attention has focused on the hypothesized role of mountain building in drawing down atmospheric carbon dioxide (CO2) via silicate weathering. However, it is now recognized that mountain building and erosion affect the carbon cycle in other important ways. For example, erosion mobilizes organic carbon (OC) from terrestrial vegetation, transferring it to rivers and sediments, and thereby acting to draw down atmospheric CO2 in tandem with silicate weathering. Meanwhile, exhumation of sedimentary rocks can release CO2 through the oxidation of rock OC and sulfide minerals. In this Review, we examine the mechanisms of carbon exchange between rocks and the atmosphere, and discuss the balance of CO2 sources and sinks. It is demonstrated that OC burial and oxidative weathering, not widely considered in most models, control the net CO2 budget associated with erosion. Lithology strongly influences the impact of mountain building on the global carbon cycle, with an orogeny dominated by sedimentary rocks, and thus abundant rock OC and sulfides, tending towards being a CO2 source. By increasing erosion, mountain building can steer the evolution of atmospheric carbon dioxide (CO2) and global climate. This Review expands from the canonical focus on silicate weathering to consider the net carbon budget of erosion, including both CO2 sinks (silicate weathering, organic-carbon burial) and CO2 sources (oxidative weathering).

Plate tectonics in the late Paleozoic

Abstract: 作为整个时间的板运动的历史， paleogeography 在塑造地质学对我们板 tectonics 和它的角色的理解基本今日。适当地欣赏 tectonicsand 的历史它对深地球和 climateit 的影响是必要的寻求 paleogeography 的一个精确、全球的模型。然而由于通过 subduction 的海洋的岩石圈的连续损失， paleogeographic 重建完整板(包括的海洋的岩石圈) 与年龄变得逐渐地挑战性。在 150 妈以前， 60% 岩石圈是失踪的，没有明确的问候，重建为海洋的岩石圈或板被开发构造原则；实际上，反映大陆人飘移的更早的 mobilistic 范例。尽管这些大陆人重建是极其有用的，披风模型下一代要求全球板有完整板的重建的运动学的描述。而且，在不顾(或仅仅泛泛地适用) 板构造规则，大陆人重建没能利用在实际限制形式的很多另外的信息。跟随一系列新开发，两个在 geodynamic 理论和分析工具，构造把自己借给由更宽的地球科学社区测试的完整板的模型现在是可行的。如此的一个模型这里被介绍为晚古生代(410250 妈) 和内在的数据的评论。尽管我们期望这个模型为数字披风建模特别地有用，我们希望它将也为理解晚古生代的 tectonics 用作一个一般框架，未来改进能在上被造并且推进的测试了。