Magmatic volatiles at rifts and arcs: Sources and fractionation effects

Mantle degassing is a fundamental process that modifies the chemical composition of the atmosphere, crust, and deep Earth. Elements are returned to the mantle from surface reservoirs through subduction at convergent margins. Melts generated in the mantle carry dissolved volatiles from depth and upon decompression exsolve a fluid or vapour phase. These volatiles drive explosive eruptions, change climate, and form economic metal deposits. Thus, the sources and processes involved in degassing of the mantle and melts are a crucial topic in geochemistry. This dissertation is composed of four chapters, each contributing original and new insights into sources and processes involved in mantle degassing. Chapters 1 and 2 focus on volatiles and the origin of carbon-rich magmatic emissions in the East African Rift, which is perhaps the least understood tectonic system on Earth in terms of mantle degassing. East Africa hosts a diverse array of enigmatic magma compositions, best exemplified by Oldoinyo Lengai volcano in Tanzania, which is the only active carbonatite volcano on Earth and an important alkaline endmember magmatic system. In Chapter 1 (published in Earth and Planetary Sciences in January, 2013) we show that nephelinite melts at Oldoinyo Lengai are the most carbon-rich natural silicate melts known to science. However, we argue that the mantle source for these melts is not unusually rich in carbon. Rather, extreme degrees of fractional crystallization and the high carbon solubility in these alkali-rich melts are responsible for the high observed carbon contents. We also show that the Oldoinyo Lengai magmatic system is rich in water, contrary to prior assumption, and that water degassing plays a fundamental role in the eruptive behaviour and magmatic evolution at Oldoinyo Lengai. The appendix to Chapter 1 contains additional data (including carbon, oxygen ,and sulfur isotope compositions and assessment of sulfur behaviour in the magma system) from Oldoinyo Lengai that have not been published. Chapter 2 presents the first bulk gas and nitrogen isotope compositions from the Rungwe Volcanic Province, which is the southernmost volcanic manifestation of rifting in East Africa. In this paper (currently in press in Chemical Geology), we show that the gases emitted at Rungwe are CO2-rich, presenting a hazard to the inhabitants of this fertile and thus heavily populated area. We find that the gas compositions record high temperatures in the deeper hydrothermal system, which could be a valuable geothermal resource for local economic development. The nitrogen isotope compositions and gas ratio tracers are consistent with an upper mantle source for the gases, and this signature is strongest in the central part of the province where the intersection of deep crustal structures provide direct conduits for mantle degassing. Interestingly, the mantle signatures are associated with the lowest temperature emissions in the region. The structures provide conduits for melts as well as gases, leading to the coincidence of mantle gas emission and volcanic edifice building in the central Rungwe Volcanic Province. These high elevation mountains are the recharge zones for the shallow aquifer and the mantle gases thus equilibrate with cold meteoric water close to the surface. Chapters 3 and 4 are studies of S degassing at rift and arc volcanoes through the use of S isotopes. Sulfur is extremely important for eruption prediction because SO2 is the only gas routinely measured remotely at active volcanoes. Explosive eruptions can inject large quantities of S into the stratosphere where it oxidizes to sulfate, which can cause decadal climate cooling. Chapter 3 examines S degassing during an explosive eruption at Anatahan (Mariana Arc) that emitted about 250 ktons of SO2 in the first ten days of the eruption. The results of this study show that the source of erupted sulfur was from ultimately from the mantle, with little addition from subducted seawater sulfate, or the pre-eruptive hydrothermal system. Sulfur isotopes fractionate during the degassing process, and the change in sulfur isotope compositions through the eruption are consistent with closed system degassing of a magma body. Chapter 4 presents a detailed assessment of the S cycle at persistently degassing basaltic volcanoes. In this study, we constrain the conditions of degassing (oxygen fugacity, temperature) as rigorously as possible to utilize S isotope compositions of gases and melts to address equilibrium versus non-equilibrium degassing and Earth\u27s sulfur cycle. We find that S degassing is not an equilibrium process and that S partitioning into the gas phase is associated with a kinetic fractionation effect reflected in the S isotope compositions. Erta Ale, a reduced magmatic system, convincingly demonstrates a kinetic effect because S2- (rather than SO42-) is the dominant S species in the melt. Equilibrium degassing should result in preferential partitioning of the heavy S isotope into the gas, however we observe that the gas is isotopically lighter than the melt. This is consistent with faster diffusion of the light isotope. At Masaya, an oxidized magmatic system, the equilibrium and kinetic isotope fractionation effects both favor isotopically light gas, which makes the contributions from equilibrium versus kinetic effects more ambiguous. However, under steady state conditions the gas phase is representative of the sulfur isotope composition of the source and the isotope composition of gas from Masaya indicates recycling of oxidized S through the subduction zone. Mass balance calculations show that only a small fraction of the S subducted at the Central American arc is returned to surface reservoirs. However, the flux of oxidized S from the subducted slab is high enough to rapidly oxidize iron in the mantle wedge, providing an explanation why arc magmas are more oxidized than those at rifts. Finally, the S retained in the subducted slab is isotopically light, potentially carrying the signature of microbial life into the deep mantle

Longitudinal study on the influence of Nd:YAG laser irradiation on microleakage associated of two filling techniques.

Objective: This study investigates the effects of Nd:YAG laser irradiation on apical and coronal seals, when used prior to two root canal filling techniques. Background Data: Limited information exists regarding the effects of morphologic changes to dentin walls following Nd: YAG laser irradiation on the sealing ability of root fillings. Methods: Two hundred forty teeth were analyzed by observing coronal and apical leakage of Indian ink (DL), and 60 were analyzed for through-and-through leakage using the fluid transport model (FTM). The Nd: YAG laser parameters were 1.5W, 100mJ, and 15Hz (four times for 5s at 20s intervals). Each group consisted of a lased and a nonlased subgroup: each subgroup had root fills done by either cold lateral condensation (CLC) or hybrid condensation (HC). Leakage was assessed after 48 h, and then at 1, 6, and 12 months. The DL group was divided into four groups of 15 teeth for each evaluation point. Through-and-through leakage (L in microliters/day) was measured for 48h under a pressure of 1.2 atm using FTM, and recorded as L = 0 (L1), 0 10 (L3). Results: Apical and coronal dye leakage was observed in all groups. Significant differences (p < 0.05) in apical leakage were found between HC and HC + Nd after 1, 6, and 12 months, and between CLC and CLC + Nd at 6 and 12 months. No significant differences were found between laser-irradiated and non-laser-irradiated groups with FTM. Conclusion: Pulsed Nd: YAG laser irradiation following root canal preparation may reduce apical leakage in association with hybrid gutta-percha condensation

Investigation of coronal leakage of root fillings after smear layer removal with EDTA or Nd:YAG lasing through capillary flow porometry

Objective: This study investigates the effects of Nd:YAG laser irradiation combined with different irrigation protocols on the marginal seal of root fillings. Background data: Limited information exists regarding the effects of morphologic changes to root canal (RC) walls after Nd:YAG laser irradiation after smear-layer removal with EDTA on the sealing ability of root fillings. Methods: The 75 root-filled teeth (5 × 15 teeth) were analyzed for through-and-through leakage by using capillary flow porometry (CFP). The RC cleaning procedure determined the assignment to a group: (1) irrigation with NaOCl 2.5% and EDTA 17% or standard protocol (SP), (2) SP + Nd:YAG lasing (dried RC), (3) NaOCl 2.5% + Nd:YAG lasing (dried RC), (4) SP + Nd:YAG lasing (wet RC), or (5) NaOCl 2.5% + Nd:YAG lasing (wet RC). Groups 1r to 5r consisted of the same filled teeth with resected apices up to the most apical point of the preparation length. Resection was performed after the first CFP measurement. Roots were filled with cold lateral condensation. CFP was used to assess minimum, mean flow and maximum pore diameters after 48 h, and immediately after these measurements, including root resection. Statistics were performed by using nonparametric tests (p > 0.05). An additional three roots per group were submitted to SEM of the RC wall. Results: Through-and-through leakage was observed in all groups. Statistically significant differences were observed in maximum pore diameter: 1r > 3r, and 1r > 5r; in mean flow pore diameter: 1r > 2r, 2r < 4r (p < 0.05). Typical Nd:YAG glazing effects were observed when the smear layer was present and exposed to the laser fiber (i.e., in the groups without use of EDTA) or when the fiber tip made direct contact with a smear-layer free RC wall. Conclusions: The reduction in through-and-through leakage is significantly higher with the Nd:YAG laser as smear-layer modifier than when smear layer is removed with an EDTA rinsing solution

An efficient algorithm to recognize local Clifford equivalence of graph states

In [Phys. Rev. A 69, 022316 (2004)] we presented a description of the action of local Clifford operations on graph states in terms of a graph transformation rule, known in graph theory as \emph{local complementation}. It was shown that two graph states are equivalent under the local Clifford group if and only if there exists a sequence of local complementations which relates their associated graphs. In this short note we report the existence of a polynomial time algorithm, published in [Combinatorica 11 (4), 315 (1991)], which decides whether two given graphs are related by a sequence of local complementations. Hence an efficient algorithm to detect local Clifford equivalence of graph states is obtained.Comment: 3 pages. Accepted in Phys. Rev.

Local invariants of stabilizer codes

In [Phys. Rev. A 58, 1833 (1998)] a family of polynomial invariants which separate the orbits of multi-qubit density operators $\rho$ under the action of the local unitary group was presented. We consider this family of invariants for the class of those $\rho$ which are the projection operators describing stabilizer codes and give a complete translation of these invariants into the binary framework in which stabilizer codes are usually described. Such an investigation of local invariants of quantum codes is of natural importance in quantum coding theory, since locally equivalent codes have the same error-correcting capabilities and local invariants are powerful tools to explore their structure. Moreover, the present result is relevant in the context of multipartite entanglement and the development of the measurement-based model of quantum computation known as the one-way quantum computer.Comment: 10 pages, 1 figure. Minor changes. Accepted in Phys. Rev.

Local permutations of products of Bell states and entanglement distillation

We present new algorithms for mixed-state multi-copy entanglement distillation for pairs of qubits. Our algorithms perform significantly better than the best known algorithms. Better algorithms can be derived that are tuned for specific initial states. The new algorithms are based on a characterization of the group of all locally realizable permutations of the 4^n possible tensor products of n Bell states.Comment: 6 pages, 1 figur

Comparative efficacy of materials used in patients undergoing pulpotomy or direct pulp capping in carious teeth: A systematic review and meta-analysis.

OBJECTIVES Different materials have been used for capping the pulp after exposure during caries removal in permanent teeth. The purpose of this study was to collate and analyze all pertinent evidence from randomized controlled trials (RCTs) on different materials used in patients undergoing pulpotomy or direct pulp capping in carious teeth. MATERIALS AND METHODS Trials comparing two or more capping agents used for direct pulp capping (DPC) or pulpotomy were considered eligible. An electronic search of four databases and two clinical trial registries was carried out up to February 28, 2021 using a search strategy properly adapted to the PICO framework. Screening, data extraction, and risk of bias (RoB) assessment of primary studies were performed in duplicate and independently. The primary outcome was clinical and radiological success; secondary outcomes included continued root formation, tooth discoloration, and dentin bridge formation. RESULTS 21 RCTs were included in the study. The RoB assessment indicated a moderate risk among the studies. Due to significant clinical and statistical heterogeneity among the studies, performing network meta-analysis (NMA) was not possible. An ad hoc subgroup analysis revealed strong evidence of a higher success of DPC with Mineral Trioxide Aggregate (MTA) compared to calcium hydroxide (CH) (odds ratio [OR] = 3.10, 95% confidence interval [CI]: 1.66-5.79). MTA performed better than CH in pulp capping (both DPC and pulpotomy) of mature compared to immature teeth (OR = 3.34, 95% CI: 1.81-6.17). The GRADE assessment revealed moderate strength of evidence for DPC and mature teeth, and low to very low strength of evidence for the remaining subgroups. CONCLUSIONS Considerable clinical and statistical heterogeneity among the trials did not allow NMA. The ad hoc subgroup analysis indicated that the clinical and radiographic success of MTA was higher than that of CH but only in mature teeth and DPC cases where the strength of evidence was moderate. PROSPERO Registration: number CRD42020127239