Paleomagnetic constraints on deformation of superfast-spread oceanic crust exposed at Pito Deep Rift

The uppermost oceanic crust produced at the superfast spreading (∼142 km Ma −1, full‐spreading rate) southern East Pacific Rise (EPR) during the Gauss Chron is exposed in a tectonic window along the northeastern wall of the Pito Deep Rift. Paleomagnetic analysis of fully oriented dike (62) and gabbro (5) samples from two adjacent study areas yield bootstrapped mean remanence directions of 38.9° ± 8.1°, −16.7° ± 15.6°, n = 23 (Area A) and 30.4° ± 8.0°, −25.1° ± 12.9°, n = 44 (Area B), both are significantly distinct from the Geocentric Axial Dipole expected direction at 23° S. Regional tectonics and outcrop‐scale structural data combined with bootstrapped remanence directions constrain models that involve a sequence of three rotations that result in dikes restored to subvertical orientations related to (1) inward‐tilting of crustal blocks during spreading (Area A = 11°, Area B = 22°), (2) clockwise, vertical‐axis rotation of the Easter Microplate (A = 46°, B = 44°), and (3) block tilting at Pito Deep Rift (A = 21°, B = 10°). These data support a structural model for accretion at the southern EPR in which outcrop‐scale faulting and block rotation accommodates spreading‐related subaxial subsidence that is generally less than that observed in crust generated at a fast spreading rate exposed at Hess Deep Rift. These data also support previous estimates for the clockwise rotation of crust adjacent to the Easter Microplate. Dike sample natural remanent magnetization (NRM) has an arithmetic mean of 5.96 A/m ± 3.76, which suggests that they significantly contribute to observed magnetic anomalies from fast‐ to superfast‐spread crust

Direct evidence from anisotropy of magnetic susceptibility for lateral melt migration at superfast spreading centers

Rare, fault‐bounded escarpments expose natural cross sections of ocean crust in several areas and provide an unparalleled opportunity to study the end products of tectonic and magmatic processes that operated at depth beneath oceanic spreading centers. We mapped the geologic structure of ocean crust produced at the East Pacific Rise (EPR) and now exposed along steep cliffs of the Pito Deep Rift near the northern edge of the Easter microplate. The upper oceanic crust in this area is typified by basaltic lavas underlain by a sheeted dike complex comprising northeast striking, moderately to steeply southeast dipping dikes. Paleomagnetic remanence of oriented blocks of dikes collected with both Alvin and Jason II indicate clockwise rotation of ∼61° related to rotation of the microplate indicating structural coupling between the microplate and crust of the Nazca Plate to the north. The consistent southeast dip of dikes formed as the result of tilting at the EPR shortly after their injection. Anisotropy of magnetic susceptibility of dikes provides well‐defined magmatic flow directions that are dominantly dike‐parallel and shallowly plunging. Corrected to their original EPR orientation, magma flow is interpreted as near‐horizontal and parallel to the ridge axis. These data provide the first direct evidence from sheeted dikes in ocean crust for along‐axis magma transport. These results also suggest that lateral transport in dikes is important even at fast spreading ridges where a laterally continuous subaxial magma chamber is present

Assessment of folate receptor-β expression in human neoplastic tissues

Over-expression of folate receptor alpha on cancer cells has been frequently exploited for delivery of folate-targeted imaging and therapeutic agents to tumors. Because limited information exists on expression of the beta isoform of the folate receptor in human cancers (FR-β), we have evaluated the immunohistochemical staining pattern of FR-β in 992 tumor sections from 20 different human cancer types using a new anti-human FR-β monoclonal antibody. FR-β expression was shown to be more pronounced in cells within the stroma, primarily macrophages and macrophage-like cells than cancer cells in every cancer type studied. Moreover, FR-β expression in both cancer and stromal cells was found to be statistically more prominent in females than males. A significant positive correlation was also observed between FR-β expression on stromal cells and both the stage of the cancer and the presence of lymph node metastases. Based on these data we conclude FR-β may constitute a good target for specific delivery of therapeutic agents to activated macrophages and that accumulation of FR-β positive macrophages in the stroma could serve as a useful indicator of a tumor's metastatic potential

A Small Molecule that Induces Intrinsic Pathway Apoptosis with Unparalleled Speed

Apoptosis is generally believed to be a process thatrequires several hours, in contrast to non-programmed forms of cell death that can occur in minutes. Our findings challenge the time-consuming nature of apoptosis as we describe the discovery and characterization of a small molecule, named Raptinal, which initiates intrinsic pathway caspase-dependent apoptosis within minutes in multiple cell lines. Comparison to a mechanistically diverse panel of apoptotic stimuli reveals that Raptinal-induced apoptosis proceeds with unparalleled speed. The rapid phenotype enabled identification of the criticalroles of mitochondrial voltage-dependent anion channel function, mitochondrial membrane potential/coupled respiration, and mitochondrial complex I, III, and IV function for apoptosis induction. Use of Raptinal in whole organisms demonstrates its utility for studying apoptosis invivo for a variety of applications. Overall, rapid inducers of apoptosis are powerful tools that will be used in a variety of settings to generate further insight into the apoptotic machinery. Palchaudhuri etal. describe the discovery of a small molecule called "Raptinal" that induces unusually rapid apoptotic cell death via the intrinsic pathway. Their work describes the utility of Raptinal as a tool for apoptosis induction relative to other available small molecules

Seismic reflection images of a near-axis melt sill within the lower crust at the Juan de Fuca ridge

Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in Nature 460 (2009): 89-93, doi:10.1038/nature08095.The oceanic crust extends over two thirds of the Earth’s solid surface and is generated along mid-ocean ridges from melts derived from the upwelling mantle. The upper and mid crust are constructed by dyking and seafloor eruptions originating from magma accumulated in mid-crustal lenses at the spreading axis, but the style of accretion of the lower oceanic crust is actively debated. Models based on geological and petrological data from ophiolites propose that the lower oceanic crust is accreted from melt sills intruded at multiple levels between the Moho transition zone (MTZ) and the mid-crustal lens, consistent with geophysical studies that suggest the presence of melt within the lower crust. However, seismic images of molten sills within the lower crust have been elusive. To date only seismic reflections from mid-crustal melt lenses and sills within the MTZ have been described, suggesting that melt is efficiently transported through the lower crust. Here we report deep crustal seismic reflections off the southern Juan de Fuca Ridge that we interpret as originating from a molten sill presently accreting the lower oceanic crust. The sill sits 5-6 km beneath the seafloor and 850-900 m above the MTZ, and it is located 1.4-3.2 km off thespreading axis. Our results provide evidence for the existence of low permeability barriers to melt migration within the lower section of modern oceanic crust forming at intermediate-to-fast spreading rates, as inferred from ophiolite studies.This research was supported by grants form the US NSF

Frozen magma lenses below the oceanic crust

Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in Nature 436 (2005): 1149-1152, doi:10.1038/nature03944.The Earth's oceanic crust crystallizes from magmatic systems generated at mid-ocean ridges. Whereas a single magma body residing within the mid-crust is thought to be responsible for the generation of the upper oceanic crust, it remains unclear if the lower crust is formed from the same magma body, or if it mainly crystallizes from magma lenses located at the base of the crust. Thermal modelling, tomography, compliance and wide-angle seismic studies, supported by geological evidence, suggest the presence of gabbroic-melt accumulations within the Moho transition zone in the vicinity of fast- to intermediate-spreading centres. Until now, however, no reflection images have been obtained of such a structure within the Moho transition zone. Here we show images of groups of Moho transition zone reflection events that resulted from the analysis of approximately 1,500 km of multichannel seismic data collected across the intermediate-spreading-rate Juan de Fuca ridge. From our observations we suggest that gabbro lenses and melt accumulations embedded within dunite or residual mantle peridotite are the most probable cause for the observed reflectivity, thus providing support for the hypothesis that the crust is generated from multiple magma bodies

Lower crustal crystallization and melt evolution at mid-ocean ridges

Author Posting. © The Author(s), 2012. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in Nature Geoscience 5 (2012): 651–655, doi:10.1038/ngeo1552.Mid-ocean ridge magma is produced when Earth’s mantle rises beneath the ridge axis and melts as a result of the decrease in pressure. This magma subsequently undergoes cooling and crystallization to form the oceanic crust. However, there is no consensus on where within the crust or upper mantle crystallization occurs1-5. Here we provide direct geochemical evidence for the depths of crystallization beneath ridge axes of two spreading centres located in the Pacific Ocean: the fast-spreading-rate East Pacific Rise and intermediate-spreading-rate Juan de Fuca Ridge. Specifically, we measure volatile concentrations in olivine-hosted melt inclusions to derive vapour-saturation pressures and to calculate crystallisation depth. We also analyse the melt inclusions for major and trace element concentrations, allowing us to compare the distributions of crystallisation and to track the evolution of the melt during ascent through the oceanic crust. We find that most crystallisation occurs within a seismically-imaged melt lens located in the shallow crust at both ridges, but over 25% of the melt inclusions have crystallisation pressures consistent with formation in the lower oceanic crust. Furthermore, our results suggest that melts formed beneath the ridge axis can be efficiently mixed and undergo olivine crystallisation in the mantle, prior to ascent into the ocean crust.This research was supported by the National Science Foundation (EAR-0646694) and the WHOI Deep Ocean Exploration Institute/Ocean Ridge Initiative.2013-02-1