USAP-DC

{"dp_type": "Project", "free_text": "Boron"}

[{"awards": "1542962 Anderson, Robert", "bounds_geometry": "POLYGON((-171 -57,-170.8 -57,-170.6 -57,-170.4 -57,-170.2 -57,-170 -57,-169.8 -57,-169.6 -57,-169.4 -57,-169.2 -57,-169 -57,-169 -57.72,-169 -58.44,-169 -59.16,-169 -59.88,-169 -60.6,-169 -61.32,-169 -62.04,-169 -62.76,-169 -63.48,-169 -64.2,-169.2 -64.2,-169.4 -64.2,-169.6 -64.2,-169.8 -64.2,-170 -64.2,-170.2 -64.2,-170.4 -64.2,-170.6 -64.2,-170.8 -64.2,-171 -64.2,-171 -63.48,-171 -62.76,-171 -62.04,-171 -61.32,-171 -60.6,-171 -59.88,-171 -59.16,-171 -58.44,-171 -57.72,-171 -57))", "dataset_titles": "Expedition Data of NBP1702; Water Mass Structure and Bottom Water Formation in the Ice-age Southern Ocean ; Water Mass Structure and Bottom Water Formation in the Ice-age Southern Ocean (SNOWBIRDS)", "datasets": [{"dataset_uid": "200166", "doi": "", "keywords": null, "people": null, "repository": "NCEI", "science_program": null, "title": "Water Mass Structure and Bottom Water Formation in the Ice-age Southern Ocean ", "url": "https://www.ncdc.noaa.gov/paleo/study/31312"}, {"dataset_uid": "200165", "doi": "", "keywords": null, "people": null, "repository": "BCO-DMO", "science_program": null, "title": "Water Mass Structure and Bottom Water Formation in the Ice-age Southern Ocean (SNOWBIRDS)", "url": "https://www.bco-dmo.org/dataset/813379/data"}, {"dataset_uid": "200126", "doi": "10.7284/907211", "keywords": null, "people": null, "repository": "R2R", "science_program": null, "title": "Expedition Data of NBP1702", "url": "https://www.rvdata.us/search/cruise/NBP1702"}], "date_created": "Fri, 25 Sep 2020 00:00:00 GMT", "description": "General:\r\nScientists established more than 30 years ago that the climate-related variability of carbon dioxide levels in the atmosphere over Earth\u2019s ice-age cycles was regulated by the ocean. Hypotheses to explain how the ocean that regulates atmospheric carbon dioxide have long been debated, but they have proven to be difficult to test. This project was designed test one leading hypothesis, specifically that the ocean experienced greater density stratification during the ice ages. That is, with greater stratification during the ice ages and the slower replacement of deep water by cold dense water formed near the poles, the deep ocean would have held more carbon dioxide, which is produced by biological respiration of the organic carbon that constantly rains to the abyss in the form of dead organisms and organic debris that sink from the sunlit surface ocean. To test this hypothesis, the degree of ocean stratification during the last ice age and the rate of deep-water replacement was to be constrained by comparing the radiocarbon ages of organisms that grew in the surface ocean and at the sea floor within a critical region around Antarctica, where most of the replacement of deep waters occurs. Completing this work was expected to contribute toward improved models of future climate change. Climate scientists rely on models to estimate the amount of fossil fuel carbon dioxide that will be absorbed by the ocean in the future. Currently the ocean absorbs about 25% of the carbon dioxide produced by burning fossil fuels. Most of this carbon is absorbed in the Southern Ocean (the region around Antarctica). How this will change in the future is poorly known. Models have difficulty representing physical conditions in the Southern Ocean accurately, thereby adding substantial uncertainty to projections of future ocean uptake of carbon dioxide. Results of the proposed study will provide a benchmark to test the ability of models to simulate ocean processes under climate conditions distinctly different from those that occur today, ultimately leading to improvement of the models and to more reliable projections of future absorption of carbon dioxide by the ocean. \r\n\r\nTechnical:\r\nThe project added a research component to an existing scientific expedition to the Southern Ocean, in the region between the Ross Sea and New Zealand, that collected sediment cores at locations down the northern flank of the Pacific-Antarctic Ridge at approximately 170\u00b0W. The goal was to collect sediments at each location deposited since early in the peak of the last ice age. This region is unusual in the Southern Ocean in that sediments deposited during the last ice age contain foraminifera, tiny organisms with calcium carbonate shells, in much greater abundance than in other regions of the Southern Ocean. Foraminifera are widely used as an archive of several geochemical tracers of past ocean conditions. We proposed to compare the radiocarbon age of foraminifera that inhabited the surface ocean with the age of contemporary specimens that grew on the seabed. The difference in age between surface and deep-swelling organisms would have been used to discriminate between two proposed mechanisms of deep water renewal during the ice age: formation in coastal polynyas around the edge of Antarctica, much as occurs today, versus formation by open-ocean convection in deep-water regions far from the continent. If the latter mechanism prevails, then it was expected that surface and deep-dwelling foraminifera would exhibit similar radiocarbon ages. In the case of dominance of deep-water formation in coastal polynyas, one expects to find very different radiocarbon ages in the two populations of foraminifera. In the extreme case of greater ocean stratification during the last ice age, one even expects the surface dwellers to appear to be older than contemporary bottom dwellers because the targeted core sites lie directly under the region where the oldest deep waters outcrop at the surface following their long circuitous transit through the deep ocean. The primary objective of the proposed work was to reconstruct the water mass age structure of the Southern Ocean during the last ice age, which, in turn, is a primary factor that controls the amount of carbon dioxide stored in the deep sea. In addition, the presence of foraminifera in the cores to be recovered provides a valuable resource for many other paleoceanographic applications, such as: 1) the application of nitrogen isotopes to constrain the level of nutrient utilization in the Southern Ocean and, thus, the efficiency of the ocean\u2019s biological pump, 2) the application of neodymium isotopes to constrain the transport history of deep water masses, 3) the application of boron isotopes and boron/calcium ratios to constrain the pH and inorganic carbon system parameters of ice-age seawater, and 4) the exploitation of metal/calcium ratios in foraminifera to reconstruct the temperature (Mg/Ca) and nutrient content (Cd/Ca) of deep waters during the last ice age at a location near their source near Antarctica. \r\n\r\nUnfortunately, the cores were shipped to the core repository in a horizontal orientation and there was sufficient distortion of the sediment that the radiocarbon ages of benthic foraminifera were uninterpretable. Therefore, we report only the radiocarbon dates for planktonic foraminifera as well as the total counts of elemental relative abundance from X-ray Fluorescence analysis of the cores. In addition, we used the expedition as an opportunity to collect water samples from which dissolved concentrations of long-lived isotope of thorium and protactinium were determined. Results from those analyses showed that lateral transport by isopycnal mixing dominates the supply of Pa to the Southern Ocean. We have also developed a new algorithm to correct for supply of Th by isopycnal mixing and thereby derive estimates of dust flux to the Southern Ocean. \r\n", "east": -169.0, "geometry": "POINT(-170 -60.6)", "instruments": null, "is_usap_dc": true, "keywords": "BIOGEOCHEMICAL CYCLES; SEDIMENT CHEMISTRY; South Pacific Ocean; SHIPS", "locations": "South Pacific Ocean", "north": -57.0, "nsf_funding_programs": "Antarctic Earth Sciences", "paleo_time": null, "persons": "Anderson, Robert; Fleisher, Martin; Pavia, Frank", "platforms": "WATER-BASED PLATFORMS \u003e VESSELS \u003e SURFACE \u003e SHIPS", "repo": "NCEI", "repositories": "BCO-DMO; NCEI; R2R", "science_programs": null, "south": -64.2, "title": "Water Mass Structure and Bottom Water Formation in the Ice-age Southern Ocean", "uid": "p0010130", "west": -171.0}, {"awards": "0228842 Grew, Edward", "bounds_geometry": "POLYGON((76 -69.3,76.05 -69.3,76.1 -69.3,76.15 -69.3,76.2 -69.3,76.25 -69.3,76.3 -69.3,76.35 -69.3,76.4 -69.3,76.45 -69.3,76.5 -69.3,76.5 -69.32,76.5 -69.34,76.5 -69.36,76.5 -69.38,76.5 -69.4,76.5 -69.42,76.5 -69.44,76.5 -69.46,76.5 -69.48,76.5 -69.5,76.45 -69.5,76.4 -69.5,76.35 -69.5,76.3 -69.5,76.25 -69.5,76.2 -69.5,76.15 -69.5,76.1 -69.5,76.05 -69.5,76 -69.5,76 -69.48,76 -69.46,76 -69.44,76 -69.42,76 -69.4,76 -69.38,76 -69.36,76 -69.34,76 -69.32,76 -69.3))", "dataset_titles": "Boron in Antarctic granulite-facies rocks: under what conditions is boron retained in the middle crust?", "datasets": [{"dataset_uid": "600030", "doi": "10.15784/600030", "keywords": "Antarctica; Chemistry:rock; Chemistry:Rock; Geochemistry; Geochronology; Solid Earth", "people": "Grew, Edward", "repository": "USAP-DC", "science_program": null, "title": "Boron in Antarctic granulite-facies rocks: under what conditions is boron retained in the middle crust?", "url": "https://www.usap-dc.org/view/dataset/600030"}], "date_created": "Tue, 10 Mar 2009 00:00:00 GMT", "description": "This award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports a project to investigate the role and fate of Boron in high-grade metamorphic rocks of the Larsemann Hills region of Antarctica. Trace elements provide valuable information on the changes sedimentary rocks undergo as temperature and pressure increase during burial. One such element, boron, is particularly sensitive to increasing temperature because of its affinity for aqueous fluids, which are lost as rocks are buried. Boron contents of unmetamorphosed pelitic sediments range from 20 to over 200 parts per million, but rarely exceed 5 parts per million in rocks subjected to conditions of the middle and lower crust, that is, temperatures of 700 degrees C or more in the granulite-facies, which is characterized by very low water activities at pressures of 5 to 10 kbar (18-35 km burial). Devolatization reactions with loss of aqueous fluid and partial melting with removal of melt have been cited as primary causes for boron depletion under granulite-facies conditions. Despite the pervasiveness of both these processes, rocks rich in boron are locally found in the granulite-facies, that is, there are mechanisms for retaining boron during the metamorphic process. The Larsemann Hills, Prydz Bay, Antarctica, are a prime example. More than 20 lenses and layered bodies containing four borosilicate mineral species crop out over a 50 square kilometer area, which thus would be well suited for research on boron-rich granulite-facies metamorphic rocks. \u003cbr/\u003e\u003cbr/\u003eWhile most investigators have focused on the causes for loss of boron, this work will investigate how boron is retained during high-grade metamorphism. Field observations and mapping in the Larsemann Hills, chemical analyses of minerals and their host rocks, and microprobe age dating will be used to identify possible precursors and deduce how the precursor materials recrystallized into borosilicate rocks under granulite-facies conditions. The working hypothesis is that high initial boron content facilitates retention of boron during metamorphism because above a certain threshold boron content, a mechanism \"kicks in\" that facilitates retention of boron in metamorphosed rocks. For example, in a rock with large amounts of the borosilicate tourmaline, such as stratabound tourmalinite, the breakdown of tourmaline to melt could result in the formation of prismatine and grandidierite, two borosilicates found in the Larsemann Hills. This situation is rarely observed in rocks with modest boron content, in which breakdown of tourmaline releases boron into partial melts, which in turn remove boron when they leave the system. Stratabound tourmalinite is associated with manganese-rich quartzite, phosphorus-rich rocks and sulfide concentrations that could be diagnostic for recognizing a tourmalinite protolith in a highly metamorphosed complex where sedimentary features have been destroyed by deformation. Because partial melting plays an important role in the fate of boron during metamorphism, our field and laboratory research will focus on the relationship between the borosilicate units, granite pegmatites and other granitic intrusives. The results of our study will provide information on cycling of boron at deeper levels in the Earth\u0027s crust and on possible sources of boron for granites originating from deep-seated rocks.\u003cbr/\u003e\u003cbr/\u003eAn undergraduate student will participate in the electron microprobe age-dating of monazite and xenotime as part of a senior project, thereby integrating the proposed research into the educational mission of the University of Maine. In response to a proposal for fieldwork, the Australian Antarctic Division, which maintains Davis station near the Larsemann Hills, has indicated that they will support the Antarctic fieldwork.", "east": 76.5, "geometry": "POINT(76.25 -69.4)", "instruments": null, "is_usap_dc": true, "keywords": "FIELD INVESTIGATION", "locations": null, "north": -69.3, "nsf_funding_programs": "Antarctic Earth Sciences", "paleo_time": null, "persons": "Grew, Edward", "platforms": "LAND-BASED PLATFORMS \u003e FIELD SITES \u003e FIELD INVESTIGATION", "repo": "USAP-DC", "repositories": "USAP-DC", "science_programs": null, "south": -69.5, "title": "Boron in Antarctic granulite-facies rocks: under what conditions is boron retained in the middle crust?", "uid": "p0000431", "west": 76.0}, {"awards": "0087235 Grew, Edward", "bounds_geometry": "POLYGON((42 -64,43.2 -64,44.4 -64,45.6 -64,46.8 -64,48 -64,49.2 -64,50.4 -64,51.6 -64,52.8 -64,54 -64,54 -64.4,54 -64.8,54 -65.2,54 -65.6,54 -66,54 -66.4,54 -66.8,54 -67.2,54 -67.6,54 -68,52.8 -68,51.6 -68,50.4 -68,49.2 -68,48 -68,46.8 -68,45.6 -68,44.4 -68,43.2 -68,42 -68,42 -67.6,42 -67.2,42 -66.8,42 -66.4,42 -66,42 -65.6,42 -65.2,42 -64.8,42 -64.4,42 -64))", "dataset_titles": null, "datasets": null, "date_created": "Mon, 09 Aug 2004 00:00:00 GMT", "description": "0087235\u003cbr/\u003eGrew\u003cbr/\u003e\u003cbr/\u003eThis award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports a project to investigate the role of beryllium in lower crustal partial melting events. The formation of granitic liquids by partial melting deep in the Earth\u0027s crust is one of the major topics of research in igneous and metamorphic petrology today. One aspect of this sphere of research is the beginning of the process, specifically, the geochemical interaction between melts and source rocks before the melt has left the source area. One example of anatexis in metamorphic rocks affected by conditions found deep in the Earth\u0027s crust is pegmatite in the Archean ultrahigh temperature granulite-facies Napier Complex of Enderby Land, East Antarctica. Peak conditions for this granulite-facies metamorphism are estimated to have reached nearly 1100 Degrees Celsius and 11 kilobar, that is, conditions in the Earth\u0027s lower crust in Archean time. The proposed research is a study of the Napier Complex pegmatites with an emphasis on the minerals and geochemistry of beryllium. This element, which is estimated to constitute 3 ppm of the Earth\u0027s upper crust, is very rarely found in any significant concentrations in metamorphic rocks subjected to conditions of the Earth\u0027s lower crust. Structural, geochronological, and mineralogical studies will be carried out to test the hypothesis that the beryllium pegmatites resulted from anatexis of their metapelitic host rocks during the ultrahigh-temperature metamorphic event in the late Archean. Host rocks will be analyzed for major and trace elements. Minerals will be analyzed by the electron microprobe for major constituents including fluorine and by the ion microprobe for lithium, beryllium and boron. The analytical data will be used to determine how beryllium and other trace constituents were extracted from host rocks under ultrahigh-temperature conditions and subsequently concentrated in the granitic melt, eventually to crystallize out in a pegmatite as beryllian sapphirine and khmaralite, minerals not found in pegmatites elsewhere. Mineral compositions and assemblages will be used to determine the evolution and conditions of crystallization and recrystallization of the pegmatites and their host rocks during metamorphic episodes following the ultrahigh-temperature event. Monazite will be analyzed for lead, thorium and uranium to date the ages of these events. Because fluorine is instrumental in mobilizing beryllium, an undergraduate student will study the magnesium fluorphosphate wagnerite in the pegmatites in order to estimate fluorine activity in the melt as part of a senior project. The results of the present project will provide important insights on the melting process in general and on the geochemical behavior of beryllium in particular under the high temperatures and low water activities characteristic of the Earth\u0027s lower crust.", "east": 54.0, "geometry": "POINT(48 -66)", "instruments": "IN SITU/LABORATORY INSTRUMENTS \u003e PROBES \u003e ELECTRON MICROPROBES; IN SITU/LABORATORY INSTRUMENTS \u003e PROBES \u003e ION MICROPROBES", "is_usap_dc": false, "keywords": "Metamorphism; Li; Be; Pegmatitic Leucosomes; Partial Melting; Lithium; Granulites; Napier Complex; Boron; Beryllium; Mineralogy; Not provided; Continental Crust", "locations": "Napier Complex", "north": -64.0, "nsf_funding_programs": "Antarctic Earth Sciences", "paleo_time": null, "persons": "Grew, Edward", "platforms": "Not provided", "repositories": null, "science_programs": null, "south": -68.0, "title": "Beryllium in Antarctic Ultrahigh-Temperature Granulite-Facies Rocks and its Role in Partial Melting of the Lower Continental Crust", "uid": "p0000370", "west": 42.0}]

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