https://www.michaelpeddy.com/research daily 0.75 2017-08-17 https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598c7d7d37c5811742913568/1502986323686/NC-MPE-523-zi.jpg Research Cathodoluminescence (CL) image taken by Joel DesOrmeau (UNR) of zircon from the rapakivi intrusive phase of the Golden horn batholith. Approximate length of the grain is 200 micrometers. Zircons separated from this intrusion have homogeneous ages and Hf isotopic compositions, making them ideal reference materials. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598c99196f4ca3b98e1b76d0/1502405896721/RankOrder.png Research Rank order plot of U-Pb dates from collaborating laboratories that use in situ U-Pb geochronological techniques. All of the results show excellent agreement with the CA-ID-TIMS date from MIT and demonstrate that GHR1 zircon is homogenous with respect to U-Pb isotopes. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598cb56ee45a7c7d97d3c08e/1502405874458/DSC_0442.jpg Research Turret for a TIMS instrument showing the sample holding apparatus with side filaments installed (left) and with only the center filament installed (right). Heating blank side filaments early in the run eliminates the need to "burn off" isobaric interferences. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598caea1cd0f6837bfcac25f/1502405882026/ Research Comparison between isotopic evolution seen using the standard warmup routine prior to a TIMS measurement of Pb and the evolution seen with the side filament warm up routine. The new routine allows us to use more data during the analysis. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598c9973e58c62a9c00b3b54/1502986586581/Baddeleyite2.png Research Traditional concordia plots showing the results for ID-TIMS and LA-ICP-MS analyses of baddeleyite from the Ogden gabbro in South Carolina (Ibañez-Mejia et al., 2015). The LA-ICP-MS data is presented showing no correction for matrix-matched fractionation, a correction using zircon, and a correction using a baddeleyite reference material. The large differences in the resulting age using these various corrections demonstrate the importance of well-calibrated reference materials for in situ analyses. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598a1ecb914e6b5b595ce645/1502335167904/ Research Geologic map and cross section of the Golden Horn batholith reproduced from Eddy et al. (2016). A: Location of the batholith (star) relative to other Mesozoic and Paleogene granitic intrusions in the North American Cordillera. B: Geologic map and sample locations. C: Cross section through the batholith from the NW to the SE. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598a21c6f5e23155afbf5e6a/1502335167907/DSC_0212.JPG Research The largest and most rapidly assembled phase of the batholith is exposed over >1.5 km of vertical relief on Mt. Hardy. Using samples collected in 2016, we are currently assessing whether there is vertical variation in texture and geochemistry in this area. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598a06ee4c0dbff7e37310de/1502335167902/ Research Meter-scale granodioritic enclaves (dark rock) within the Golden Horn batholith. The enclaves represent hotter, less evolved magma that intruded into a crystal-rich granitic magma and cooled quickly. If you look closely you can see crystals that were entrained in the enclaves during intrusion. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598cdc11914e6b91aeb41e36/1502403669063/DSC_0375.JPG Research A thick package of rhyolitic tuffs overlying the Searchlight pluton. The paired intrusive and extrusive record of this magmatic system may help shed light on the processes that lead to eruption and the timescales over which they occur. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598a208b17bffc79a0bb5c3f/1502335167905/DSC_0221.JPG Research Exposure of the Golden Horn batholith's roof on Mt. Azurite. Seen as dark metasedimentary rocks overlying lighter colored granite. The extreme topographic relief made it possible to calculate robust volumes for each intrusive phase of the batholith. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598cd077e4fcb5f4432a9c8a/1502401741233/KoryakWill-32.jpg Research Mud on the tracks of the "Snowcat" that we used to travel across the tundra to the sampling locality. Photo courtesy of Will Steinhardt. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598cd339cd0f688dea606307/1502401645822/KoryakWill-97.jpg Research Panorama of a river valley in the Koryak Mountains in Chukotka, Russia. Photo courtesy of Will Steinhardt. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598ccf8a49fc2be90921c5c6/1502400425146/MacPherson2013a.png Research Geologic map from MacPherson et al. (2013) of the quasicrystal sample locality (star) based on our own mapping and mapping by the Russian geologic survey. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598cc2e0914e6b91aeb267b1/1502405942540/Maloof2010a.png Research Graph showing the evolution of the carbon isotope, U, and V composition of carbonates in Morocco during the early Cambrian from Maloof et al. (2010). Both U and V are normalized and corrected for silicic sedimentary input using Th content and the post-Archean average shale composition. We interpreted these negative trends to represent increasing levels of dissolved oxygen in Earth's ocean during this time. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598cba521e5b6c9f35e32e63/1502394992639/DSC_0425.JPG Research Miocene ash beds in lacustrine sedimentary rock near Clarkia, Idaho. Dating tuffs such as these using high-precision U-Pb geochronology remains the gold standard in generating stratigraphic age models. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598b4bc9bebafb782fcc47d9/1502986179508/iodp_1277_core_ruler.jpg Research Magmatic veins intruding serpentinized peridotite in ODP Core 1277 from the Newfoundland rifted margin. Here the basement is composed of exhumed subcontinental lithospheric mantle, intruded by highly evolved gabbroic veins. Photo is from the International Ocean Discovery Program. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598b7723d2b857b923e1491d/1502312234350/Rift.png Research Cartoon of mantle exhumation along a lithospheric-scale detachment fault prior to plate rupture and initial seafloor spreading from Eddy et al. (2017). This model may explain why magmatism and mantle exhumation was time-transgressive from east to west and the narrow region of exhumed mantle on the Newfoundland margin compared to the Iberia margin. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598b4e48d2b8578f99654939/1502301850556/ Research The hafnium isotopic composition of magmatic veins intruding exhumed mantle on the Newfoundland and Iberia margins is consistent with their derivation from depleted Atlantic mantle (DAM), not enriched plume-related mantle, which could be younger and unrelated to rifting (Eddy et al., 2017). https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598bb996cd39c3692cbebebe/1502329270477/ Research Eocene pillow lavas in the Crescent Formation along the northern shore of the Olympic Peninsula. These rocks were erupted in a submarine environment adjacent to the Eocene subduction zone. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598bb22ce6f2e1a6fa261f6f/1502327390845/DSC_0009.JPG Research Sequential basalt flows in the Western Ghats just to the north of Mahabaleshwar. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598bb68dcd0f686159cda6bd/1502328549243/DSC_0037.JPG Research Clasts of basalt within a mafic tuff between Pune and Mahabaleshwar. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598b74f2f43b55f3c6132f67/1502311744257/ Research Paleosol (red bole) between two basalt flows within the Deccan Traps. Here you can see the paleosol forming a thick mantle between the flows and filling voids in the flow top breccia of the lower flow. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598bbadc4c0dbf58c6d46920/1502405656961/DSC_0183.JPG Research Pegmatitic gabbro on the shores of Lake Wynoochie, southern Olympic Peninsula. Late stage, pegmatitic zones like this typically bear zircons and are prime targets for geochronologic sampling in mafic terranes. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598cd590cd39c338ea4e295c/1502401978556/Differentiation.jpg Research Coupled geochronologic and geochemical constraints on the timescale of magmatic differentiation from alkaline basalt to quart monzonite in the Dariv Complex, Mongolia from Bucholz et al. (2017). https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598a2d3e17bffc79a0bc5127/1502228538215/GabbroBSE.jpg Research Back scattered electron (BSE) image of zircon included in clinopyroxene in a monzogabbro within the Dariv igneous complex. Textural constraints on the position of zircon within this suite of rocks allowed us to assess whether it represented an early or late crystallizing phase. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598cd6587131a549796e018a/1502402204112/Alkaline.jpg Research We concluded that early zircon saturation in the Dariv complex is related to elevated Zr concentrations in the parental basalt. In this graph reproduced from Bucholz et al. (2016), we show that high Zr content may be common in primitive alkaline melts. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598b62cef14aa1659209ec7c/1502308830020/ Research A large xenolith of ca. 51 Ma sandstone within a ca. 49 Ma basaltic dike. This dike is part of the Teanaway dike swarm that intruded a large forearc sedimentary basin immediately after the basin was folded ca. 50 Ma. We have linked basin disruption and emplacement of this dike swarm to events along the continental margin, including passage of a triple-junction. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598b579e03596e10c7b70010/1502985687222/DSC02313.JPG Research Clast of flow-banded rhyolite within conglomerate in the uppermost Chumstick Formation, Washington. We used zircons separated from this clast to constrain the maximum depositional age of this unit. This age constraint, among many others, was used to make regional correlations between Eocene non-marine sedimentary units throughout Washington. These correlations helped create a robust age model for sedimentation, faulting, and magmatism during Eocene ridge-trench interaction. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598b60e28419c2bcfb587b59/1502306922603/DSC_0132.jpg Research Mylonitic orthogneiss within the Ross Lake fault zone. Part of this project has involved constraining the timing of motion on major strike-slip faults throughout Washington. Near this location, the Ross Lake fault zone was sealed at 48.5 Ma by the Skymo layered mafic intrusion. These relationships were constrained by an undergraduate thesis by Yuem Park (Berkeley) that I co-advised. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598b6cffe45a7c9c24a1daa0/1502406019492/ Research Our proposed plate reconstruction for ca. 50 Ma modified from Bradley et al. (1993), showing southward migration of the Kula-Farallon oceanic spreading center along the British Columbian coast and accretion of the Siletzia terrane to Washington, Oregon, and southern Vancouver Island. https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598a0b10e3df28c8a476c8bc/1502219095365/NC-MPE-523-zi.jpg Research https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598a4e6c17bffc79a0be7cd0/1502236276375/DSC02313.JPG Research https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598a54ae15d5db14ee405487/1502237892346/DSC_0087.JPG Research https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598b4ad049fc2b97647d8614/1502300895808/iodp_1277_core_no_ruler.jpg Research https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598b944ff5e23155afd4ab17/1502335167900/DSC_0251+%283%29.jpg Research https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598b99cdcd39c355dc8e094b/1502321105441/GabbroBSE+%284%29.jpg Research https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598b9ead1e5b6cbabcae54cd/1502322366239/KoryakWill-33.jpg Research https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/598cba1c37c5812c282c2ed4/1502394927020/DSC_0425.JPG Research https://www.michaelpeddy.com/mpeddy-cv daily 0.75 2018-10-16 https://www.michaelpeddy.com/about daily 1.0 2019-08-21 https://static1.squarespace.com/static/5988e9c37131a5dd4b52623d/t/5989fa60f5e23155afbc4d24/1502214819296/ About https://www.michaelpeddy.com/news daily 0.75 2018-10-04