Phase relationships of S-type granite with H2_O to 35 kbar: Muscovite granite from Harney Peak, South Dakota

Muscovite granite (13.8% muscovite, 4.8% normative corundum) was reacted, with varying percentages of H_2O, in cold-seal vessels at 2 kbar and in piston-cylinder apparatus between 10 and 35 kbar. The diagrams illustrating melting/crystallization relationships are: P-T sections with both excess H_2O and with no H_2O added (0.66% H_2O in rock); T-X_(H_2O) sections at 15 kbar and 25 kbar showing H_2O-undersaturated conditions; the H_2O-undersaturated surface for the crystallization of quartz/coesite (small amounts of aluminosilicate minerals persist to higher temperatures). Glass compositions measured by electron microprobe from samples with 5% H_2O at 15 kbar confirm that liquids are syenitic through at least 100°C above the solidus, as predicted from the effect of pressure on the Residua System. Results are explained successfully by phase relationships involving muscovite, quartz, and orthoclase in K_2O-Al_2O_3-SiO_2-H_2O, with reactions depicted in a P_(total)-P_(e_(H_2O))-T model, with special reference to the divariant surfaces in the region P_(e_(H_2O)) < P_(total). With reduced P_(e_(H_2O)) (or a_(H_2O)), produced either by small amounts of H_2O (and H_2O-undersaturation) or by CO_2 + H_2O mixtures, subsolidus dehydration reaction temperatures decrease, vapor-present solidus temperatures increase, and muscovite stability in presence of liquid increases. In general, muscovite, biotite, and amphibole can be precipitated from magmas containing only a few tenths per cent H_2O (although the H_2O-undersaturated liquids coexisting with crystals may contain 3% or more dissolved H_2O). This particular granite cannot be a primary magma from mantle or subducted oceanic crust. It is a possible product of partial fusion of pelitic rocks between about 20 km and 40 km depth given sufficient H2O, and xenocrystal muscovite or sillimanite from the source rocks. The phase relationships are consistent with the idea of S-type granites, but not sufficient to prove the origin of this rock. Additional tests require phase relationships of other associated granitic rocks, and details of geochemistry, geophysics, and field relationships

Breakdown of Angular Momentum Selection Rules in High Pressure Optical Pumping Experiments

We present measurements, using two complementary methods, of the breakdown of atomic angular momentum selection rules in He-broadened Rb vapor. Atomic dark states are rendered weakly absorbing due to fine-structure mixing during Rb-He collisions. The effect substantially increases the photon demand for optical pumping of dense vapors

Solidity of viscous liquids. IV. Density fluctuations

This paper is the fourth in a series exploring the physical consequences of the solidity of highly viscous liquids. It is argued that the two basic characteristics of a flow event (a jump between two energy minima in configuration space) are the local density change and the sum of all particle displacements. Based on this it is proposed that density fluctuations are described by a time-dependent Ginzburg-Landau equation with rates in k-space of the form $\Gamma_0+Dk^2$ with $D\gg\Gamma_0a^2$ where $a$ is the average intermolecular distance. The inequality expresses a long-wavelength dominance of the dynamics which implies that the Hamiltonian (free energy) may be taken to be ultra local. As an illustration of the theory the case with the simplest non-trivial Hamiltonian is solved to second order in the Gaussian approximation, where it predicts an asymmetric frequency dependence of the isothermal bulk modulus with Debye behavior at low frequencies and an $\omega^{-1/2}$ decay of the loss at high frequencies. Finally, a general formalism for the description of viscous liquid dynamics, which supplements the density dynamics by including stress fields, a potential energy field, and molecular orientational fields, is proposed

Hydrous Carbonatitic Liquids Drive CO2 Recycling From Subducted Marls and Limestones

This research was supported by the Italian Ministry of Education, University, and Research (MIUR) program PRIN2017 and by the Deep Carbon Observatory (DCO). We are greatly indebted to Andrea Risplendente for careful examination of run charges at the Electron Microprobe.Pelagic limestones are subducted in a variety of subduction zones worldwide. Despite the geochemical relevance of systems enriched in CaCO3, previous experimental investigations mostly focused on carbonated pelites, with low Ca/(Ca+Mg+Fe) ratio. We present the compositions and the formation conditions of liquids in the model system CaO‐Al2O3‐SiO2‐H2O‐CO2 (CASHC), building on phase relationships in the subsystems CHC and CSHC, where a second critical endpoint was suggested at temperatures as low as 515 °C, and 3.2 GPa. Multianvil experiments were performed at 4.2 and 6.0 GPa on five bulk compositions at variable Ca/Si/Al ratios. H2O contents vary from 5.6 to 21 wt%. Aragonite + kyanite + vapor and minor lawsonite form at 700 °C, replaced by zoisite/grossular at 800 °C. Between 850 °C and 950 °C, a complex sequence of textural features is observed upon quenching of a single volatile‐rich liquid phase formed at run conditions. Precipitates include dendritic CaCO3, silicate glass, and Al‐rich whiskers. The bulk composition of such hydrous carbonatitic liquids is retrieved by image analysis on X‐ray maps, showing Ca/Si ratio increasing with pressure and temperature. Hydrous Ca‐carbonatitic liquids are efficient media for scavenging volatiles from subducted crustal material and for metasomatizing the mantle wedge.Ministry of Education, Universities and Research (MIUR)Deep Carbon Observatory (DCO

Colorectal carcinoma in Hong Kong: epidemiology and genetic mutations.

The incidence of colorectal carcinoma is rising at an alarming pace in Asian urban societies such as Hong Kong. Detailed examination of the epidemiological pattern and genetic mutation of colorectal cancer in the Hong Kong Chinese population is overdue. We compared the reported age incidence of colorectal carcinoma in Hong Kong with that of Scotland and other countries. Hong Kong showed a much higher incidence of colorectal carcinoma among the young age groups. By comparison with other countries, this raised incidence among the young appeared to be related to southern Chinese societies. The recent dramatic rise in colorectal cancer in Hong Kong was largely attributable to an increase in the over 50 years age group, while the young incidence remained unchanged. We also defined the mutation spectrum of p53 and Ki-ras in 67 unselected cases by direct DNA sequencing. Interestingly, insertion/deletion mutations in p53 from colorectal carcinoma in Hong Kong showed a significantly higher frequency (17.2%) than the Scottish data (0%) and the world database (6.6%), although the overall frequency of p53 mutation (43%) in Hong Kong was similar to others. The high incidence of colorectal carcinoma in young people and the raised proportion of frameshift mutations in p53 encourage further search for a genetic basis for susceptibility to this disease in the Hong Kong Chinese population

Prophylactic acid-suppression medication to prevent anastomotic strictures after oesophageal atresia surgery: a systematic review and meta-analysis

Background Anastomotic stricture is a common postoperative complication of oesophageal atresia ± tracheoesophageal fistula (OA/TOF) repair. Acid gastro-oesophageal reflux disease (GORD) is considered to be a factor in stricture formation and acid suppression medication is recommended post-operatively in consensus guidance. We aimed to investigate whether patients who were treated prophylactically with acid suppression medication had a reduced incidence of strictures compared to those who did not receive it. Methods A systematic review of studies was performed, searching multiple databases without language or date restrictions. Multiple reviewers independently assessed study eligibility and literature quality. The primary outcome was anastomotic stricture formation, with secondary outcomes of GORD, anastomotic leak, and oesophagitis. Meta-analysis was performed using a random effects model, and the results were expressed as an odds ratio (OR) with 95% confidence intervals (CI). Results No randomised studies on the topic were identified. Twelve observational studies were included in the analysis with ten reporting the primary outcome. The quality assessment showed a high risk of bias in several papers, predominantly due to non-objective methods of assessment of oesophageal stricture and the non-prospective, non-randomised nature of the studies. Overall, 1395 patients were evaluated, of which 753 received acid suppression medication. Meta-analysis revealed a trend towards increased odds of anastomotic strictures in infants receiving prophylactic medication, but this was not statistically significant (OR 1.33; 95% CI 0.92, 1.92). No significant differences were found in secondary outcomes. Conclusions This meta-analysis found no evidence of a statistically significant link between the prophylactic prescribing of acid suppression medication and the risk of developing anastomotic stricture after OA repair. The literature in this area is limited to observational studies and a randomised controlled trial is recommended to explore this question