IODP Expeditions 309 and 312 drill an intact section of upper oceanic basement into gabbros

The Integrated Ocean Drilling Program's (IODP) Expeditions 309 and 312 successfully completed the first sampling of an intact section of upper oceanic crust, through lavas and the sheeted dikes into the uppermost gabbros. Hole 1256D, which was initiated on the Ocean Drilling Program's (ODP) Leg 206, now penetrates to >1500 mbsf and >1250 m sub-basement. The first gabbroic rocks were encountered at 1407 mbsf. Below this, the hole penetrates 3c100 m into a complex zone of fractionated gabbros intruded into contact metamorphosed dikes

Data report: trace element, Sr isotope, and Ge/Si composition of fluids and sediments in ridge-flank low-temperature hydrothermal environments

The data presented in this report demonstrate significant improvements in the ability to constrain trace element and Sr isotopic concentrations in sediments overlying ridge-flank hydrothermal systems. Improved sampling methods orchestrated by the Integrated Ocean Drilling Program (i.e., advanced piston coring and anoxic sample processing) enabled the collection of reactive pore water species with minimal alteration and sampling artifacts. Improved methods of high-resolution inductively coupled plasma–mass spectrometry trace element analysis, including the use of the 8-hydroxyquinoline functional group to extract and preconcentrate rare earth elements and other trace metals, were used to compile a data set of 28 trace element concentrations and 87Sr/86Sr ratios. From this extensive data set, we were able to increase the current understanding of how redox-reactive species respond to diagenic processes. Near-basement trends were used in combination with the known composition of hydrothermal fluids that exit Baby Bare Springs to asses our ability to predict basement fluid compositions using sediment pore water profiles collected by deep-sea drilling. The results show that prediction of basement fluid composition is possible for many trace elements, provided the near-basement concentration gradients are minimal. In order to place the Ge/Si systematics in a broader context, pore water and borehole fluid Ge and Si data are presented from additional sites across the Juan de Fuca Ridge flank and from two additional ridge-flank settings. These data show that Ge concentrations and Ge/Si ratios are much higher in the basement fluids than in the basal sediments because of increased mobilization of Ge relative to Si within the basement hydrothermal reservoir. Solid-phase sediment data are presented, highlighted by the occurrence of Mn- and carbonate-rich layers.<br/

Linking basement carbonate vein compositions to porewater geochemistry across the eastern flank of the Juan de Fuca Ridge, ODP Leg 168

Leg 168 of the Ocean Drilling Program (ODP) investigated the heat flow, fluid chemistry and crustal alteration associated with ridge flank hydrothermal systems. Ten sites were drilled on the eastern flank of the Juan de Fuca Ridge, along an 80 km transect, between 20 and 100 km east of the spreading centre. Recovered cores consisted of 100-500 m of sediment with shallow penetration (1.7-48.1 m) into the underlying igneous basement (0.8-3.6 Ma). Here we use the composition of calcium carbonate minerals, from veins within the upper basement, to reconstruct the evolving chemistry of hydrothermal fluids with increasing crustal age and sediment cover thickness. We show for the first time a clear link between the alteration of the basement rocks as recorded by secondary minerals, and the near-basement sedimentary pore fluids, which are often assumed to be representative of the basement fluids responsible for low temperature alteration of the upper crust. Carbonates precipitated from basement fluids that ranged in strontium isotopic composition from near-modern seawater (87Sr/86Sr[ap]0.70918) to the near-basement pore fluid values at any one site. 87Sr/86Sr ratios are independent of mineralogy with both aragonite and calcite precipitating from variably evolved fluids with the range in carbonate 87Sr/86Sr increasing with crustal age. A parallel geochemical evolution of basement fluids and sediment porewaters is shown since 87Sr/86Sr ratios of near-basement pore fluids decrease from 0.709013 to 0.707108 away from the ridge axis. A correlation exists between 87Sr/86Sr ratios and [delta]18O-calculated fluid temperatures, with more geochemically evolved carbonates having precipitated from warmer fluids. Basement fluid compositions, calculated from carbonate Sr, Mg, Fe and Mn concentrations combined with suitable partition coefficients, are also temperature-dependent. Given an observed increase in basement temperature with age, from 16[deg]C to 64[deg]C along the transect, a progressive chemical development of basement fluid is demonstrated. Carbonate veins in volcanic basement from ODP Holes 504B and 896A, on the Costa Rica Rift, record the same temperature compositional evolution of basement fluid as those from the Juan de Fuca Ridge flank. Although these locations have different thermal histories and therefore must have experienced different temporal geochemical evolution of basement fluid, basement temperature appears to be the dominant control on basement fluid composition

Incidence rates of surgically treated rhegmatogenous retinal detachment among manual workers, non-manual workers and housewives in Tuscany, Italy

PurposeCandidate risk factors for idiopathic rhegmatogenous retinal detachment (RRD) include heavy manual handling (requiring Valsalva’s maneuver). We assessed incidence rates of surgically treated idiopathic RRD among manual workers, non-manual workers and housewives resident in Tuscany, Italy.MethodsWe retrieved all hospital discharge records bearing a principal diagnosis corresponding to RRD coupled with retinal surgery for any resident of Tuscany during 1997–2009. After elimination of repeated admissions and patients with coexistent, associated conditions (including recent trauma), subjects aged 25–59 years were classified as manual workers, non-manual workers or housewives. Population data were extracted from the 2001 census.ResultsWe identified 1,946 eligible cases (1,142 men). Among men, manual workers experienced a 1.8-fold higher age-standardized rate per 100,000 person-years than non-manual workers [17.4 (95 % confidence interval (CI) 16.1–18.7) vs. 9.8 (95 % CI 8.8–10.8)]. Age-standardized rates among women were 1.9-fold higher for manual workers [11.1 (95 % CI 9.8–12.3)] and 1.7-fold higher for housewives [9.5 (95 % CI 8.3–10.8)] than in non-manual workers [5.7 (95 % CI 4.8–6.6)].ConclusionsThis large population-based study suggests that manual workers are affected by idiopathic RRD requiring surgical treatment more often than non-manual workers. The higher rates of surgically treated RRD experienced by manual workers are in accord with the hypothesis that heavy manual handling may have a causal role.<br/