How do oceanic plateaus form? Clues from drilling at Shatsky Rise

Oceanic plateaus are huge basaltic constructions whose eruptions may briefly outstrip even global mid-ocean ridge magma production. Although they form great undersea mountains, their origins are poorly understood. A widely accepted explanation is that oceanic plateaus are built by massive eruptions from the head of nascent thermal mantle plumes that rise from deep in the mantle to the surface [e.g., Duncan and Richards, 1991]. An alternative is that plateaus erupt by decompression melting of fusible patches in the upper mantle at plate edges or zones of extension [Foulger, 2007]

IODP Expedition 324: Ocean Drilling at Shatsky Rise Gives Clues about Oceanic Plateau Formation

Integrated Ocean Drilling Program (IODP) Expedition 324 cored Shatsky Rise at five sites (U1346–U1350) to study processes of oceanic plateau formation and evolution. Site penetrations ranged from 191.8 m to 324.1 m with coring of 52.6 m to 172.7 m into igneous basement at four of the sites. Average recovery in basement was 38.7%–67.4%. Cored igneous sections consist mainly of variably evolved tholeiitic basalts emplaced as pillows or massive flows. Massive flows are thickest and make up the largest percentage of section on the largest and oldest volcano, late Jurassic age Tamu Massif; thus, it may have formed at high effusion rates. Such massive flows are characteristic of flood basalts, and similar flows were cored at Ontong Java Plateau. Indeed, the similarity of igneous sections at Site U1347 with that cored on Ontong Java Plateau implies similar volcanic styles for these two plateaus. On younger, smaller Shatsky Rise volcanoes, pillow flows are common and massive flows thinner and fewer, which might mean volcanism waned with time. Cored sediments from summit sites contain fossils and structures implying shallow water depths or emergence at the time of eruption and normal subsidence since. Summit sites also show pervasive alteration that could be due to high fluid fluxes. A thick section of volcaniclastics cored on Tamu Massif suggests that shallow, explosive submarine volcanism played a significant role in the geologic development of the plateau summit. Expedition 324 results imply that Shatsky Rise began with massive eruptions forming a huge volcano and that subsequent eruptions waned in intensity, forming volcanoes that are large, but which did not erupt with unusually high effusion rates. Similarities of cored sections on Tamu Massif with those of Ontong Java Plateau indicate that these oceanic plateaus formed in similar fashion

Formation and evolution of Shatsky Rise oceanic plateau: Insights from IODP Expedition 324 and recent geophysical cruises

Recent research from the Shatsky Rise in the western Pacific Ocean provides new insights on the formation and evolution of this oceanic plateau as well as tests of mantle models to explain anomalous large igneous province (LIP) volcanism. Recent Shatsky Rise studies cored the igneous pile (Integrated Ocean Drilling Program Expedition 324), imaged the interior with seismic refraction and multichannel seismic reflection data, and mapped magnetic anomalies adjacent to the plateau to provide new constraints on its tectonic history. Coring data show that Tamu Massif, the largest edifice within Shatsky Rise, is characterized by massive sheet flows, similar to flows caused by voluminous eruptions in continental flood basalts. Core data also indicate that the massive eruptions waned as the plateau evolved and smaller edifices were built. Seismic data show intrabasement reflectors within Tamu Massif that indicate volcanism from its center, indicating that this is an enormous shield volcano with abnormally low flank slopes and thick crust (~ 30 km). Paleomagnetic data record minimal geomagnetic field variations, consistent with the inference of massive, rapid volcanism. Altogether, the physical picture indicates that Shatsky Rise was built by massive, rapid eruptions that formed enormous volcanoes. Geochronologic data support the previously inferred age progression, with the volcanic massifs formed along the trace of a triple junction starting from Tamu Massif and becoming progressively younger to the northeast. These data weaken support for rapid emplacement because they show that the last eruptions atop Tamu Massif encompassed several million years between the final massive flows as well as a long hiatus of ~ 15 Myr until late stage eruptions that formed a summit ridge. They may also indicate that the last eruptions on Tamu and Ori massifs occurred while the triple junction was hundreds of kilometers distant. Furthermore, magnetic anomaly data indicate that the plate boundary reorganization associated with Shatsky Rise formation occurred several million years prior to the first Tamu Massif eruptions, suggesting plate boundary control of Shatsky Rise initiation. Geochemical and isotopic data show that Shatsky Rise rocks are variably enriched, with the majority of lavas being similar to mid-ocean ridge basalts (MORB). However, the data indicate deeper (> 30 km) and higher partial degree of melting (15–23%) as compared with normal MORB. Melting models indicate that the magma experienced a mantle temperature anomaly, albeit only a small one (~ 50 °C). Some lava compositions suggest the involvement of recycled subducted slab material. Recent investigations of Shatsky Rise initially envisaged a competition between two end-member models: the thermal plume head and the fertile mantle melting beneath plate extension (aka, plate model). Both hypotheses find support from new data and interpretations, but both do not fit some data. As a result, neither model can be supported without reservation. Noting that most basaltic oceanic plateaus have formed at triple junctions or divergent plate boundaries, we suggest that this dichotomy is artificial. Oceanic plateau volcanism is anomalous and focused at spreading ridges for reasons that are still poorly understood, mainly owing to uncertainties about mantle convection and geochemical reservoirs. Shatsky Rise investigations have vastly improved our understanding of the formation of this oceanic plateau, but highlight that important work remains to understand the underlying nature of this volcanism

Geochemistry and Age of Shatsky, Hess, and Ojin Rise seamounts: Implications for a connection between the Shatsky and Hess Rises

Shatsky Rise in the Northwest Pacific is the best example so far of an oceanic plateau with two potential hotspot tracks emanating from it: the linear Papanin volcanic ridge and the seamounts comprising Ojin Rise. Arguably, these hotspot tracks also project toward the direction of Hess Rise, located ∼1200 km away, leading to speculations that the two plateaus are connected. Dredging was conducted on the massifs and seamounts around Shatsky Rise in an effort to understand the relationship between these plateaus and associated seamounts. Here, we present new 40Ar/39Ar ages and trace element and Nd, Pb, and Hf isotopic data for the recovered dredged rocks and new trace elements and isotopic data for a few drill core samples from Hess Rise. Chemically, the samples can be subdivided into plateau basalt-like tholeiites and trachytic to alkalic ocean-island basalt compositions, indicating at least two types of volcanic activity. Tholeiites from the northern Hess Rise (DSDP Site 464) and the trachytes from Toronto Ridge on Shatsky’s TAMU massif have isotopic compositions that overlap with those of the drilled Shatsky Rise plateau basalts, suggesting that both Rises formed from the same mantle source. In contrast, trachytes from the southern Hess Rise (DSDP Site 465A) have more radiogenic Pb isotopic ratios that are shifted toward a high time-integrated U/Pb (HIMU-type mantle) composition. The compositions of the dredged seamount samples show two trends relative to Shatsky Rise data: one toward lower 143Nd/144Nd but similar 206Pb/204Pb ratios, the other toward similar 143Nd/144Nd but more radiogenic 206Pb/204Pb ratios. These trends can be attributed to lower degrees of melting either from lower mantle material during hotspot-related transition to plume tail or from less refractory shallow mantle components tapped during intermittent deformation-related volcanism induced by local tectonic extension between and after the main volcanic-edifice building episodes on Shatsky Rise. The ocean-island-basalt-like chemistry and isotopic composition of the Shatsky and Hess rise seamounts contrast with those formed by purely deformation-related shallow mantle-derived volcanism, favoring the role of a long-lived mantle anomaly in their origin. Finally, new 40Ar/39Ar evidence indicates that Shatsky Rise edifices may have been formed in multiple-stages and over a longer duration than previously believed

Quantification of cAMP and cGMP analogs in intact cells: pitfalls in enzyme immunoassays for cyclic nucleotides

Immunoassays are routinely used as research tools to measure intracellular cAMP and cGMP concentrations. Ideally, this application requires antibodies with high sensitivity and specificity. The present work evaluates the cross-reactivity of commercially available cyclic nucleotide analogs with two non-radioactive and one radioactive cAMP and cGMP immunoassay. Most of the tested cyclic nucleotide analogs showed low degree competition with the antibodies; however, with Rp-cAMPS, 8-Br-cGMP and 8-pCPT-cGMP, a strong cross-reactivity with the corresponding cAMP and cGMP, respectively, immunoassays was observed. The determined EIA-binding constants enabled the measurement of the intracellular cyclic nucleotide concentrations and revealed a time- and lipophilicity-dependent cell membrane permeability of the compounds in the range of 10–30% of the extracellular applied concentration, thus allowing a more accurate prediction of the intracellular analog levels in a given experiment

Strategien und Technologien einer pluralistischen Fern- und Nahwärmeversorgung in einem liberalisierten Energiemarkt unter besonderer Berücksichtigung der Kraft-Wärme-Kopplung und erneuerbarer Energien : Kurzfassung der Studie

Die Zusammenfassung dient zwei Zielen: Zunächst werden die wesentlichen Ergebnisse der Langfassung der o.g. Studie referiert; auf dieser Basis werden dann mögliche Maßnahmen und Strategien diskutiert, die kurzfristig (2000-2001) ergriffen werden könnten. Als Akteure kommen hierbei nicht nur die Bundesregierung, die wichtige Rahmenbedingungen zum Marktgeschehen wird setzen müssen, in den Fokus, sondern auch die Betreiber von Heizkraftwerken und KWK-Anlagen und deren Verbände, aber auch andere Akteure wie z. B. Contracting-Unternehmen und Forschungseinrichtungen. Da die Übergangsphase der Liberalisierung der europäischen Stromwirtschaft in den Jahren 2000-2005 eine besondere Herausforderung für die KWK-Entwicklung darstellt, wird auch ein kurzfristig wirksames Maßnahmenbündel zur Diskussion gestellt. Dem Leser sei zum Verständnis in Erinnerung gerufen, dass diese vorgelegte Analyse im Rahmen einer Vorstudie durchgeführt wurde und langfristig abgesicherte Aussagen auch Analysen mit einschließen müssten, die bis 2010 und 2020 reichen. Weiterführende Arbeiten sollen in einer geplanten Hauptstudie erfolgen

Strategien und Technologien einer pluralistischen Fern- und Nahwärmeversorgung in einem liberalisierten Energiemarkt unter besonderer Berücksichtigung der Kraft-Wärme-Kopplung und regenerativer Energien : Kurztitel: Pluralistische Wärmeversorgung ; AGFW-Hauptstudie - erster Bearbeitungsabschnitt. Band 1, Grundlagen der Kraft-Wärme-Kopplung, Zertifizierungsverfahren und Fördermodelle

Die im vorliegenden Band 1 vorgestellten Ergebnisse sollen der Begleitung der anstehenden KWK-Gesetzgebung in technischer und wirtschaftlicher Hinsicht dienen. Das derzeitige KWK-(Vorschalt-)Gesetz, welches durch ein neues mit klareren Kriterien verbundenes Gesetz ersetzt werden soll, ist in mehrfacher Hinsicht problematisch, da es Regelungen zum Auffangen von Stranded Investments mit Regelungen zur Förderung von KWK vermischt, keine klare Definition von KWK enthält, industrielle KWK ausgegrenzt und durch die intransparente Förderstruktur das Mittelaufkommen und die Mittelverwendung nicht nachvollziehbar macht. Ein KWK-Ausbau wird sich in der gegenwärtigen Situation des Strommarktes nur auf der Basis einer Förderung entwickeln können (vgl. Vorstudie). Obwohl neue KWK-Anlagen im Vergleich zu neuen Anlagen der ungekoppelten Erzeugung unter Vollkostenbedingungen meist günstiger abschneiden, benötigen sie vor dem Hintergrund des aktuell auf dem Niveau kurzfristiger Grenzkosten geführten Preiskampfes zusätzliche Deckungsbeiträge. Die Analyse der Vielzahl vorgeschlagener Zertifizierungskriterien hat ergeben, dass definierter KWK-Strom eine geeignete Messgröße darstellt. Ausführliche Analysen zeigen, dass die Bestimmung dieses Stromanteils mit Hilfe einer einmaligen Anlagenzertifizierung relativ unproblematisch ist. Eine weitere Differenzierung des so definierten KWK-Stroms, z. B. hinsichtlich der CO2-Effizienz, birgt dagegen die Gefahr so krasser Fördergegensätze zwischen alten und neuen Anlagen sowie zwischen gas- und kohlegefeuerten Anlagen, dass dadurch vorhandene, für zukünftige Anwendungen prädestinierte Standorte verloren gehen könnten und die sinnvolle Auskopplung großer Wärmemengen aus Steinkohlekraftwerken unterbleibt. Die Bewertung verschiedener Fördermodelle ergibt kein eindeutiges Bild, welches Fördermodell zu bevorzugen wäre. Andererseits zeigt sich, dass sich aus allen Bausteinen von Förderinstrumenten ein sinnvolles Instrumentenmix konstruieren lässt