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

Links to Analytical Facilities Available at Binghamton University

JEOL-8900 'Super Probe'
X-ray diffractometer

Recent Research Projects by D. Jenkins

• Stability and crystal-chemistry of ferro-actinolite, in collaboration with Krassimir Bozhilov (University of California – Riverside)
• Mechanism of nucleation and growth of tremolitic amphibole from oxides, in collaboration with Krassimir Bozhilov and David Veblen (Johns Hopkins University)
• Role of water content on the synthesis of glaucophane
• Low-pressure stability of glaucophane relative to talc and albite
• Formation conditions of Na-Mg-rich triple-chain silicates
• Relative stability of double- and triple-chain silicates
  

Recently Completed Research Projects by Graduate Students

• Juan Carlos Corona – Investigated the reaction of glaucophane and quartz to talc and albite in the range of 600-750°C and 0.7-2.2 GPa.  This reaction serves as a model for the blueschist-to-greenschist facies transition and is the geologically relevant boundary for the low-pressure stability of end-member glaucophane.  By defining the location of this boundary we are better able to define the pressures at which high-pressure (blueschist-facies) metamorphism occurs in nature.
  
  
• Haroldo Lledo – Obtained compositional half-brackets on the iron content of actinolitic amphibole equilibrated in the presence of orthopyroxene and clinopyroxene over the range of 600-890°C and 0.1-0.4 GPa.  These half-brackets provided important limiting experimental data on the change in the stability of actinolitic amphibole with temperature, for which there are very few data in the literature.  He also investigated the upper-thermal stability of one particular natural actinolite (Fe# = 0.22) to demonstrate that this phase does indeed have a high thermal stability (maximum of 860°C at 0.4 GPa).  This study has applications to both the realm of metamorphic rocks, where actinolite is a very common mineral, and igneous rocks, where actinolite is found in some Kiruna-type iron-ore deposits.  Investigation of the formation of actinolite coexisting with immiscible iron-rich melts separated from andesitic magma was done in conjunction with Prof. Naslund.
  
  
• Bridget McCollam (Ams) – Synthesized large quantities of the triple-chain silicate Na_3.34Mg_8.16Si₁₂O_30.46(OH)_6.74 and of the nearly iso-chemical double-chain silicate Na_2.26Mg_5.45Si₈O_21.26(OH)_2.64 for the dual purposes of (1) experimentally investigating the phase equilibrium boundary between these two minerals in pressure-temperature space, and (2) making calorimetric measurements of their enthalpies of formation and third-law entropies.  This study is the first to provide definitive calorimetric data for a triple-chain silicate, which, in turn, provides a valuable basis for determining if this class of minerals has any stability field or whether they are completely metastable relative to other minerals.  Using the data from this study it is possible to show that this triple-chain silicate could form from ultramafic rocks (from chrysotile and talc) in an oceanic environment but only far from mid-ocean ridges.
  
  

Journal Publications: (Last 5 years)

• Driscall, J., Jenkins, D.M., Dyar, M.D., and Bozhilov, K.N. (2005) Cation ordering in synthetic low-calcium actinolite.  American Mineralogist, 90, 900-911.
• Senda, K., Ishida, K., and Jenkins, D.M. (2005) X-ray Rietveld refinement and FTIR spectra of synthetic (Si,Ge)-richterites.  American Mineralogist, 90, 1062-1071.
• Jenkins, D. M. and Corona, J. C. (2006) The role of water in the synthesis of glaucophane.  American Mineralogist, 91, 1055-1068.
• Jenkins, D. M. and Corona, J. C. (2006) Molar volume and thermal expansion of glaucophane.  Physics and Chemistry of Minerals, 33, 356-362.
• Bozhilov, KN., Brownstein, D., and Jenkins, D.M. (2007) Biopyribole evolution during tremolite synthesis from dolomite and quartz in CO₂-H₂O fluid.  American Mineralogist, 92, 898-908.
• Corona, J. C. and Jenkins, D. M. (2007) An experimental investigation of the reaction: glaucophane + 2 quartz = 2 albite + talc.  European Journal of Mineralogy, 19, 147-158.
• Lledo, H. L. and Jenkins, D. M. (2008) Experimental investigation of the upper-thermal stability of Mg-rich actinolite; Implications for Kiruna type iron deposits. Journal of Petrology, 49, 225-238.
• Ishida, I., Jenkins, D. M., and Hawthorne, F. C. (2008) Mid-IR bands of synthetic calcic amphiboles of tremolite-pargasite series and of natural calcic amphiboles. American Mineralogist, 93, 1112-1118.
• 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 (in press)