Effects of variable magma supply on mid-ocean ridge eruptions : constraints from mapped lava flow fields along the Galápagos Spreading Center

Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 13 (2012): Q08014, doi:10.1029/2012GC004163.Mapping and sampling of 18 eruptive units in two study areas along the Galápagos Spreading Center (GSC) provide insight into how magma supply affects mid-ocean ridge (MOR) volcanic eruptions. The two study areas have similar spreading rates (53 versus 55 mm/yr), but differ by 30% in the time-averaged rate of magma supply (0.3 × 106 versus 0.4 × 106 m3/yr/km). Detailed geologic maps of each study area incorporate observations of flow contacts and sediment thickness, in addition to sample petrology, geomagnetic paleointensity, and inferences from high-resolution bathymetry data. At the lower-magma-supply study area, eruptions typically produce irregularly shaped clusters of pillow mounds with total eruptive volumes ranging from 0.09 to 1.3 km3. At the higher-magma-supply study area, lava morphologies characteristic of higher effusion rates are more common, eruptions typically occur along elongated fissures, and eruptive volumes are an order of magnitude smaller (0.002–0.13 km3). At this site, glass MgO contents (2.7–8.4 wt. %) and corresponding liquidus temperatures are lower on average, and more variable, than those at the lower-magma-supply study area (6.2–9.1 wt. % MgO). The differences in eruptive volume, lava temperature, morphology, and inferred eruption rates observed between the two areas along the GSC are similar to those that have previously been related to variable spreading rates on the global MOR system. Importantly, the documentation of multiple sequences of eruptions at each study area, representing hundreds to thousands of years, provides constraints on the variability in eruptive style at a given magma supply and spreading rate.This work was supported by the National Science Foundation grants OCE08–49813, OCE08–50052, and OCE08– 49711.2013-02-2

Urological cancer care pathways: development and use in the context of systematic reviews and clinical practice guidelines

Background: Making healthcare treatment decisions is a complex process involving a broad stakeholder base including patients, their families, health professionals, clinical practice guideline developers and funders of healthcare. Methods: This paper presents a review of a methodology for the development of urological cancer care pathways (UCAN care pathways), which reflects an appreciation of this broad stakeholder base. The methods section includes an overview of the steps in the development of the UCAN care pathways and engagement with clinical content experts and patient groups. Results: The development process is outlined, the uses of the urological cancer care pathways discussed and the implications for clinical practice highlighted. The full set of UCAN care pathways is published in this paper. These include care pathways on localised prostate cancer, locally advanced prostate cancer, metastatic prostate cancer, hormone-resistant prostate cancer, localised renal cell cancer, advanced renal cell cancer, testicular cancer, penile cancer, muscle invasive and metastatic bladder cancer and non-muscle invasive bladder cancer. Conclusion: The process provides a useful framework for improving urological cancer care through evidence synthesis, research prioritisation, stakeholder involvement and international collaboration. Although the focus of this work is urological cancers, the methodology can be applied to all aspects of urology and is transferable to other clinical specialties.11 page(s

Eruptive timing and 200 year episodicity at 92°W on the hot spot-influenced Galapagos Spreading Center derived from geomagnetic paleointensity

Eruptive timing in mid-ocean ridge systems is relatively poorly constrained, despite being an important variable in our understanding of many mid-ocean ridge processes, including volcanic construction; magma recharge, flux, and storage; and the stability of hydrothermal systems and biological communities. Only a handful of absolute eruption chronologies exist, yet they are essential in understanding how eruptive timing varies with important controlling variables. To construct an eruptive history at one location on the Galapagos Spreading Center, we present age determinations derived from geomagnetic paleointensity. To aid interpretation of the paleointensity data, we also present results from on-bottom magnetic anomaly measurements and forward modeling of topographic-induced magnetic anomalies. Anomalies may lead to a 1–2 µT bias in flow-mean paleointensities, which does not significantly affect the overall interpretation. Paleointensity results for the three youngest sampled units are indistinguishable, consistent with the flows being emplaced in relatively rapid succession. Comparisons with models of geomagnetic field behavior suggest these flows were erupted sometime in the past 100–200 years. The fourth sampled unit has a significantly higher paleointensity, consistent with an age of roughly 400 years. The possible bias in paleointensity data allows for ages as young as ~50 years for the youngest three flows and 200–400 years for the oldest flow. This age distribution demonstrates an episodicity in the emplacement of the largest flows at this location, with a 200–300 year period of relative quiescence between emplacement of the oldest unit and the three youngest units