David M. Jenkins

jenkins desk

Professor of Geology

     PhD 1980 University of Chicago
     Science I, Room 267
     (607) 777-2736
     dmjenks@binghamton.edu

Areas of Research

  • Experimental Petrology
    • Stability of common minerals at crustal and upper-mantle pressures and temperatures
    • Equilibrium chemical reactions between minerals and aqueous solutions
    • Non-equilibrium aspects of mineral formation
      • Reaction mechanisms and rates of mineral growth
      • Diffusion rates of anions and cations
    • Extraction of thermodynamic data derived from experimental mineral equilibria
  • Crystal Chemistry
    • Chemical substitutions in common minerals
    • Distribution of cations within mineral structures
    • Changes in crystal lattice with changes in chemical composition
  • Metamorphic Petrology
    • Geothermometry and geobarometry of metamorphosed mafic rocks
    • Fluid rock interactions at high pressures and temperatures
Photos

Links to Analytical Facilities Available at Binghamton University

JEOL-8900 'Super Probe'
X-ray diffractometer

 

Recent Research Projects by D. Jenkins

  • Experimental investigation of reactions modeling the greenschist-facies to blueschist-facies transition
  • Unit-cell dimensions, volume compressibility, and equation-of-state studies of synthetic glaucophane
  • Crystal-chemistry of amphiboles along the tremolite-glaucophane join
  • Use of the autocorrelation analysis of infrared spectra to determine the amount of asymmetry in a mineral solvus or miscibility gap
  • Chlorine incorporation in calcium amphiboles

 

Recently Completed Research Projects by Graduate Students

  • Ashley Basora – Investigations into the lower-pressure stability of glaucophane + paragonite + quartz as a possible model for the transition from blueschist- to greenschist-facies has led to some rather surprising conclusions.  Although this assemblage was originally presumed to produce chlorite + albite at lower pressures, it was discovered that an expandable phyllosilicate (tri-octahedral smectite) appeared consistently and reproducibly instead of chlorite. Ashley was able to demonstrate that chlorite in the presence of glaucophane would convert to smectite with increasing temperature! The resultant investigation of the reaction of glaucophane + paragonite + quartz to smectite
    + albite in the range of 600-800°C provides direct evidence for the high-temperature stability of smectite, suggesting that tri-octahedral smectite may be a stable mineral in high-grade metamorphic terranes.

  • Nick Holsing – Nick has been researching the topic of trace element (Si, Mg) incorporation into diamond as a potential geothermometer or geobarometer. The purpose of this project is to test whether trace-element concentrations in diamonds themselves, not just mineral inclusions, can be used to deduce the temperatures and/or pressures where
    diamonds form. This project has been challenging because of the high temperatures (1400-1800°C) and pressures (5-8 GPa) involved as well as the difficulty of growing diamond and analyzing the newly formed diamond for the low quantities (100-1000 ppm) of Si and Mg present. Analyses of diamond overgrowths on seed diamonds treated in the presence of olivine, enstatite, and garnet and a suitable flux (pyrrhotite, iron-nickel metal) suggests there is a temperature dependence of the Si content. Research continues on this project.

  • Jie Lei –Understanding the energetics of cation mixing between calcium- and sodium-calcium amphiboles, minerals that are typical of greenschist- and blueschist-facies rocks, is needed if one is to deduce such things as the depths to which rocks have been subducted in high-pressure metamorphic rocks.  The energetics of cation mixing can, in turn, be deduced from the shape and size of the miscibility gap that exists between calcium- and sodium-amphiboles. Jie synthesized amphiboles along the hornblende-glaucophane (Ca2Mg4Al(AlSi7)O22(OH)2-Na2Mg3Al2Si8O22(OH)2) join over the range of 720-780°C and 1.5-2.5 GPa for the purpose of determine volume-composition relations and for doing autocorrelation analysis of their infrared spectra. Compositional re-equilibration experiments were also done to define the temperature limit of the miscibility gap. The resultant miscibility gap was modeled thermodynamically and the thermodynamic data used to calibrate the change in the Na and Al content of amphiboles with changes in the
    temperature and depth of subduction.

 

Recently Completed Research Projects by Under-Graduate Students
  • Zachary Holmes – Zach synthesized a series of carbonates along the calcite-dolomite join for the purpose of determining how accurately autocorrelation analysis of their mid-
    and far-infrared spectra modeled the known enthalpy of mixing for these carbonates. His results indicated that the mid-infrared spectra, in contrast to the more widely accepted thought that the far infrared spectra, better modeled the enthalpy of mixing data. This study provides additional support for the use of this novel analytical method (autocorrelation) for deducing the thermodynamics of cation mixing in mineral solid solutions.

  • Greg Salwen – Greg investigated the formation of tri-octahedral smectite from a series of bulk compositions along the talc-paragonite (Mg3Si4O10(OH)2-NaAl2(AlSi3)O10(OH)2) join. He found the highest yield of smectite to be at about 60 mol% of the talc component at 600°C and 1.2 GPa. He was also able to demonstrate the high thermal stability of this smectite, being stable up to 875°C at 0.3 GPa before decomposing to a liquid-pyroxene-spinel assemblage. This work further demonstrates that tri-octahedral smectite may occur stably in high-grade metamorphic rocks.
  •  Albert Chan - Al investigated the saturation limit of chlorine incorporation into the amphibole ferropargasite at 700°C and 0.2 GPa near the magnetite-wuestite oxygen buffer. His results showed that the amount of Cl substitution into OH-bearing amphibole reaches a plateau at a brine concentration of about 1.5 m NaCl but that the total Cl concentration in the amphibole only amounts to about 2% substitution of Cl for OH. This research has raised interesting questions about how natural amphiboles form with 50-60% substitution of Cl for OH.

     

    Journal Publications: (Last 5 years)

    • Jenkins, D. M., Carpenter, M. A., and Zhang., M. (2013) Experimental and infrared characterization of the miscibility gap along the tremolite-glaucophane join. American Mineralogist (in press).
    • Corona, J. C., Jenkins, D. M., and Holland, T. J. B. (2013) Constraints on the upper pressure stability of blueschist facies metamorphism along the reaction: glaucophane = talc + 2 jadeite in the Na2O-MgO-Al2O3-SiO2-H2O system.  American Journal of Science, 313, 967-995.
    • Jagniecki, E. A., Jenkins, D. M., Lowenstein, T. K., and Carroll, A.R. (2013) Experimental study of shortite (Na2Ca2(CO3)3) formation and application to the burial history of the Wilkins Peak Member, Green River Basin, Wyoming, USA. Geochimica et Cosmochimica Acta, 115, 31-45.
    • Jenkins, D. M., Della Ventura, G., Oberti, R., and Bozhilov, K. (2013) Synthesis and characterization of amphiboles along the tremolite–glaucophane join. American Mineralogist, 98, 588-600.
    • Jenkins, D.M., Gilleaudeau, G.J., Kawa, C., Dibiase, J.M., and Fokin, M. (2012) Compositional limits and analogues of monoclinic triple-chain silicates. Contributions to Mineralogy and Petrology, 164, 229-244.
    • Basora, A. M., Jenkins, D. M., and Bish, D. L. (2012) The lower-pressure stability of glaucophane in the presence of paragonite and quartz in the system Na2O-MgO-Al2O3-SiO2-H2O. American Mineralogist, 97, 713-726.
    • Jenkins, D. M. (2011) The transition from blueschist to greenschist facies modeled by the reaction glaucophane + 2 diopside + 2 quartz = tremolite + 2 albite. Contributions to Mineralogy and Petrology, 162:725–738. DOI 10.1007/s00410-011-0621-8.
    • Ams, B. E. and Jenkins, D. M. (2011) Formation conditions for triple-chain silicates. American Mineralogist, 96, 814-819. DOI: 10.2138/am.2011.3568.
    • Jenkins, D.M., Corona, J. C., Bassett, W. A., Mibe, K., and Wang, Z. (2010) Compressibility of synthetic glaucophane. Physics and Chemistry of Minerals, 37, 219-226, doi 10.1007/s00269-009-0326-y.
    • Ams, B. E., Jenkins, D. M., Boerio-Goates, J., Morcos, R. M., Navrotsky, A., and Bozhilov, K. N. (2009) Thermochemistry of a synthetic Na-Mg rich triple-chain silicate: determination of thermodynamic variables. American Mineralogist, 94, 1242-1254.

    Questions or comments: dmjenks@binghamton.edu

Last Updated: 8/14/14