The link between volcanism and plutonism in epizonal magma systems; high-precision U–Pb zircon geochronology from the Organ Mountains caldera and batholith, New Mexico

The Organ Mountains caldera and batholith expose the volcanic and epizonal plutonic record of an Eocene caldera complex. The caldera and batholith are well exposed, and extensive previous mapping and geochemical analyses have suggested a clear link between the volcanic and plutonic sections, making this an ideal location to study magmatic processes associated with caldera volcanism. Here we present high-precision thermal ionization mass spectrometry U–Pb zircon dates from throughout the caldera and batholith, and use these dates to test and improve existing petrogenetic models. The new dates indicate that Eocene volcanic and plutonic rocks in the Organ Mountains formed from ~44 to 34 Ma. The three largest caldera-related tuff units yielded weighted mean [superscript 206]Pb/[superscript 238]U dates of 36.441 ± 0.020 Ma (Cueva Tuff), 36.259 ± 0.016 Ma (Achenback Park tuff), and 36.215 ± 0.016 Ma (Squaw Mountain tuff). An alkali feldspar granite, which is chemically similar to the erupted tuffs, yielded a synchronous weighted mean [superscript 206]Pb/[superscript 238]U date of 36.259 ± 0.021 Ma. Weighted mean [superscript 206]Pb/[superscript 238]U dates from the larger volume syenitic phase of the underlying Organ Needle pluton range from 36.130 ± 0.031 to 36.071 ± 0.012 Ma, and the youngest sample is 144 ± 20 to 188 ± 20 ka younger than the Squaw Mountain and Achenback Park tuffs, respectively. Younger plutonism in the batholith continued through at least 34.051 ± 0.029 Ma. We propose that the Achenback Park tuff, Squaw Mountain tuff, alkali feldspar granite and Organ Needle pluton formed from a single, long-lived magma chamber/mush zone. Early silicic magmas generated by partial melting of the lower crust rose to form an epizonal magma chamber. Underplating of the resulting mush zone led to partial melting and generation of a high-silica alkali feldspar granite cap, which erupted to form the tuffs. The deeper parts of the chamber underwent continued recharge and crystallization for 144 ± 20 ka after the final eruption. Calculated magmatic fluxes for the Organ Needle pluton range from 0.0006 to 0.0030 km3/year, in agreement with estimates from other well-studied plutons. The petrogenetic evolution proposed here may be common to many small-volume silicic volcanic systems

The 2018 Lake Louise Acute Mountain Sickness Score.

Roach, Robert C., Peter H. Hackett, Oswald Oelz, Peter Bärtsch, Andrew M. Luks, Martin J. MacInnis, J. Kenneth Baillie, and The Lake Louise AMS Score Consensus Committee. The 2018 Lake Louise Acute Mountain Sickness Score. High Alt Med Biol 19:1-4, 2018.- The Lake Louise Acute Mountain Sickness (AMS) scoring system has been a useful research tool since first published in 1991. Recent studies have shown that disturbed sleep at altitude, one of the five symptoms scored for AMS, is more likely due to altitude hypoxia per se, and is not closely related to AMS. To address this issue, and also to evaluate the Lake Louise AMS score in light of decades of experience, experts in high altitude research undertook to revise the score. We here present an international consensus statement resulting from online discussions and meetings at the International Society of Mountain Medicine World Congress in Bolzano, Italy, in May 2014 and at the International Hypoxia Symposium in Lake Louise, Canada, in February 2015. The consensus group has revised the score to eliminate disturbed sleep as a questionnaire item, and has updated instructions for use of the score

Imitators of exercise-induced bronchoconstriction

Exercise-induced bronchoconstriction (EIB) is described by transient narrowing of the airways after exercise. It occurs in approximately 10% of the general population, while athletes may show a higher prevalence, especially in cold weather and ice rink athletes. Diagnosis of EIB is often made on the basis of self-reported symptoms without objective lung function tests, however, the presence of EIB can not be accurately determined on the basis of symptoms and may be under-, over-, or misdiagnosed. The goal of this review is to describe other clinical entities that mimic asthma or EIB symptoms and can be confused with EIB

Respiratory effect of beta-blocker eye drops in asthma: population-based study and meta-analysis of clinical trials

Aims: To measure the prevalence of beta-blocker eye drop prescribing and respiratory effect of ocular beta-blocker administration in people with asthma. Methods: We measured the prevalence of ocular beta-blocker prescribing in people with asthma and ocular hypertension, and performed a nested case–control study (NCCS) measuring risk of moderate exacerbations (rescue steroids in primary care) and severe exacerbations (asthma hospitalization) using linked data from the UK Clinical Practice Research Datalink. We then performed a systematic review and meta-analysis of clinical trials evaluating changes in lung function following ocular beta-blocker administration in people with asthma. Results: From 2000 to 2012, the prevalence of non-selective and selective beta-blocker eye drop prescribing in people with asthma and ocular hypertension fell from 23.0% to 13.4% and from 10.5% to 0.9% respectively. In the NCCS, the relative incidence (IRR) of moderate exacerbations increased significantly with acute non-selective beta-blocker eye drop exposure (IRR 4.83, 95% CI 1.56–14.94) but not with chronic exposure. In the meta-analysis, acute non-selective beta-blocker eye drop exposure caused significant mean falls in FEV1 of −10.9% (95% CI −14.9 to −6.9), and falls in FEV1 of ≥20% affecting one in three. Corresponding values for selective beta-blockers in people sensitive to ocular non-selective beta-blockers was −6.3% (95% CI −11.7 to −0.8), and a non-significant increase in falls in FEV1 of ≥20%. Conclusion: Non-selective beta-blocker eye drops significantly affect lung function and increase asthma morbidity but are still frequently prescribed to people with asthma and ocular hypertension despite safer agents being available