Abstract Seismic and magnetotelluric studies suggest hydrous silicate melts atop the 410 km discontinuity form 30–100 km thick layers. Importantly, in some regions, two layers are observed. These stagnant layers are related to their comparable density to the surrounding mantle, but their formation mechanisms and detailed structures remain unclear. Here we report a large decrease of silicate melt viscosity at ~14 GPa, from 96(5) to 11.7(6) mPa⋅s, as water content increases from 15.5 to 31.8 mol% H₂O. Such low viscosities facilitate rapid segregation of melt, which would typically prevent thick layer accumulation. Our 1D finite element simulations show that continuous dehydration melting of upwelling mantle material produces a primary melt layer above 410 km and a secondary layer at the depth of equal mantle-melt densities. These layers can merge into a single thick layer under low density contrasts or high upwelling rates, explaining both melt doublets and thick single layers.
more »
« less
DensityX: A program for calculating the densities of magmatic liquids up to 1,627°C and 30 kbar
Here we present a standalone program, DensityX, to calculate the densities of hydrous silicate melts (1000s of samples in a single model run) given pressures, temperatures, and major oxide compositions in wt.% in the 10-component system SiO2-TiO2-Al2O3-Fe2O3-FeO-MgO-CaO-Na2O-K2O-H2O. We use DensityX to analyze over 3,000 melt inclusions over a wide compositional range to visualize the distribution of natural silicate liquid densities in the Earth’s crust. The program is open-source, written in Python, and can be accessed and run via an online interface through a web browser at https://densityx.herokuapp.com or by downloading and running the code from a github repository. A companion Excel spreadsheet can also be used to run density calculations identical to those in the Python script but only for one sample at a time. In another example application, we demonstrate how DensityX can be used to constrain density-driven convective cycling in the phonolitic lava lake of Erebus volcano, Antarctica.
more »
« less
- Award ID(s):
- 1654584
- PAR ID:
- 10587158
- Publisher / Repository:
- Volcanica
- Date Published:
- Journal Name:
- Volcanica
- Volume:
- 2
- Issue:
- 1
- ISSN:
- 2610-3540
- Page Range / eLocation ID:
- 1 to 10
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Density of silicate melt dictates melt migration and establishes the gross structure of Earth's interior. However, due to technical challenges, the melt density of relevant compositions is poorly known at deep mantle conditions. Particularly, water may be dissolved in such melts in large amounts and can potentially affect their density at extreme pressure and temperature conditions. Here we perform first‐principles molecular dynamics simulations to evaluate the density of Fe‐rich, eutectic‐like silicate melt (Emelt) with varying water content up to about 12 wt %. Our results show that water mixes nearly ideally with the nonvolatile component in silicate melt and can decrease the melt density significantly. They also suggest that hydrous melts can be gravitationally stable in the lowermost mantle given its likely high iron content, providing a mechanism to explain seismically slow and dense layers near the core‐mantle boundary.more » « less
-
We simulate the possibility of scaling channel formation to low density plasmas of low atomic number gas over a large range of pulse duration including (1) pulses up to 300 ps in duration, using inverse bremsstrahlung (IB) heating and (2) ultrashort pulses up to 100s of femtoseconds for generating tenuous plasmas of centimeter to meter lengths by optical field ionization (OFI). Results show IB heating up to tens of eV, and channels formed from an initial density of 1e18 cm-3 with axial densities as low as 1e17cm-3 and radius of 50 microns. It has been shown that centimeter-scale waveguides can be generated via OFI heating at densities of approximately 1e17 cm-3. Lastly, we outline the experimental setup to be used in future experiments at the University of Texas Tabletop Terawatt (UT3) facility.more » « less
-
null (Ed.)Abstract Quantum computers and algorithms can offer exponential performance improvement over some NP-complete programs which cannot be run efficiently through a Von Neumann computing approach. In this paper, we present BayeSyn, which utilizes an enhanced stochastic program synthesis and Bayesian optimization to automatically generate quantum programs from high-level languages subject to certain constraints. We find that stochastic synthesis can comparatively and efficiently generate a program with a lower cost from the high dimensional program space. We also realize that hyperparameters used in stochastic synthesis play a significant role in determining the optimal program. Therefore, BayeSyn utilizes Bayesian optimization to fine-tune such parameters to generate a suitable quantum program.more » « less
-
Call graphs have many applications in software engineering, including bug-finding, security analysis, and code navigation in IDEs. However, the construction of call graphs requires significant investment in program analysis infrastructure. An increasing number of programming languages compile to the Java Virtual Machine (JVM), and program analysis frameworks such as WALA and SOOT support a broad range of program analysis algorithms by analyzing JVM bytecode. This approach has been shown to work well when applied to bytecode produced from Java code. In this paper, we show that it also works well for diverse other JVM-hosted languages: dynamically-typed functional Scheme, statically-typed object-oriented Scala, and polymorphic functional OCaml. Effectively, we get call graph construction for these languages for free, using existing analysis infrastructure for Java, with only minor challenges to soundness. This, in turn, suggests that bytecode-based analysis could serve as an implementation vehicle for bug-finding, security analysis, and IDE features for these languages. We present qualitative and quantitative analyses of the soundness and precision of call graphs constructed from JVM bytecodes for these languages, and also for Groovy, Clojure, Python, and Ruby. However, we also show that implementation details matter greatly. In particular, the JVM-hosted implementations of Groovy, Clojure, Python, and Ruby produce very unsound call graphs, due to the pervasive use of reflection, invokedynamic instructions, and run-time code generation. Interestingly, the dynamic translation schemes employed by these languages, which result in unsound static call graphs, tend to be correlated with poor performance at run time.more » « less
An official website of the United States government

