Leonid Neymark

Biography

I am currently a Research Chemist in the Geology, Geophysics, and Geochemistry Science Center after being transferred from the Geochemistry Team, Yucca Mountain Project Branch where I conducted U-series studies of soils, fracture minerals and water-rock interaction processes.  My area of expertise is isotope geochemistry and geochronology. I received my MS degree in Radiochemistry and Ph.D. in Geochemistry in St. Petersburg, Russia. As a deputy head of the Isotope lab at the Institute for Precambrian Geology and Geochronology, Russian Academy of Sciences, I conducted isotope-geochemical research of Precambrian rocks and ore deposits utilizing Rb-Sr, Sm-Nd and U-Th-Pb isotope systems. My first project with the USGS was on lower crustal granulites in 1992 and I joined Yucca Mountain Project Branch, WRD in 1993.

I conduct a wide spectrum of isotope-geochemical studies involving radiogenic isotopes of U, Pb, Sr, and Nd and using ICP-MS and TIMS techniques. Before 2010 I was a principal investigator and a member of the Geochemistry Team in the Yucca Mountain Project Branch, WRD. The team’s task was to evaluate geochemical aspects of the hydrogeologic suitability of Yucca Mountain to permanently store high-level radioactive waste. My focus was on the history of secondary mineral deposition (largely calcite and silica) in soil and unsaturated- and saturated-zone settings and on isotope-geochemical indicators of water-rock interaction as evidence of past water flow. These studies used U-Pb and U-series and other isotope-geochemical methods to characterize the timing of low-temperature surface processes of mineral deposition and to evaluate past water-rock interaction. In 2004 I was closely involved in the installation and detailed testing of a new ThermoFinnigan thermal-ionization mass-spectrometer Triton. I developed reproducible mass-spectrometric methods of U-series isotope measurements for whole rock samples with large Th/U and 232Th/230Th ratios. Previous YMPB work included systematic characterization of subsurface and soil hydrogenic minerals to provide a basis for understanding past hydrologic and climate variability in the Yucca Mountain region.  

 

My current projects:

  • Sources of Pb contamination in domestic well water in SW Missouri
  • Matrix Pore Waters – Ultracentrifugation Method for Low-Permeability Sedimentary and Crystalline Rocks
  • The U-Th-Pb whole-rock isotope system in the Chalk River core and past redox conditions
  • Impact of Exhalative Hydrothermal Systems on Marine Chemistry: Applications for  Mineral Assessment
  • Conditions and Processes Affecting Radionuclide Transport (writing a chapter for the GSA Memoir devoted to Yucca Mountain, volume 2)

Prior to joining the YMPB I was leading and participating in a number of projects involving application of isotope geochemistry and geochronology to studies of Precambrian rocks and ore deposits. In general, these studies sought to determine the source of matter and timing of processes responsible for mineral formation. Also, a certain part of my career was devoted to the development of new approaches and techniques in isotope-geochemistry and geochronology.

 

PREVIOUS PROFESSIONAL POSITIONS

2001 – 2004. S.M. Stoller Corporation, Senior Geochemist. I continued to work for the YMPB, USGS. PI for studies of U-series radioactive disequilibrium in waters and rocks at the Yucca Mountain area as an indication of low-temperature water-rock interaction processes. Involved in36Cl isotope–geochemical studies aimed to constrain water percolation processes through the thick unsaturated zone at Yucca Mountain. I developed applications of SIMS ion-microprobe techniques for dating of uraniferous opal using U-series (together with J. Paces and J. Wooden, USGS) and U-Pb (together with A. Nemchin, Curtin University, Western Australia) methods.

1996 – 2001.   Pacific Western Technologies, Ltd. Senior Scientist-I. I continued to work for the YMPB, USGS. Involved in U-series disequilibrium isotope-geochemical studies of waters and secondary minerals at the Yucca Mountain area. PI on the implementation of U-Pb dating of Neogene-Quaternary opals with initial radioactive disequilibrium. Worked on development of mass-spectrometric isotope dilution analysis of femtogram amounts of Ra.

1993 - 1996.  US Geological Survey Visiting Research Scientist. I was involved in design and implementation of geochemical studies directed largely at the evaluation of Yucca Mountain in southern Nevada as a potential site for the storage of nuclear waste. In 1995 completed a report (Neymark et al., 1995, USGS OFR 95-134) summarizing studies that evaluated fault zones as potential pathways for hydrothermal fluids with regard to precious metal mineralization. I conducted critical research on the U and Th geochemistry of low temperature calcite and opal with particular emphasis on U-series and U-Pb dating using thermal ionization mass-spectrometric technique. Co-author of five USGS-YMPB Milestone reports on Paleohydrology and Paleoclimate of the Yucca Mountain area.

1985 - 1993.  Institute of Precambrian Geology and Geochronology (IPGG), St. Petersburg, Russian Academy of Sciences. Senior research scientist and deputy head of the laboratory for isotope geology and geochronology. Chief of a group conducting geochronological and isotope-geochemical studies of Precambrian rocks and ore deposits using the Rb-Sr, Sm-Nd and U-Th-Pb isotope systems. Co-chair of the monthly isotope-geochemical seminar.

1985-1989. PI in a part of the IPGG Project "Geochronological Scale of the Precambrian" devoted to the Baikal region, Eastern Siberia. This part of the Project used U-Pb zircon dating of igneous and volcanic rocks to constrain ages of major Late Precambrian geologic events in the region.

1988-1992. Scientific Secretary of Russian working group for an international project “The Oldest Rocks on Earth”, UNESCO International Geological Correlation Program (IGCP) Project #280. Chief: A. Kröner (Germany). I was responsible for organizing and conducting an international scientific meeting and a field trip to the Aldan Shield, Eastern Siberia (1989) and also was a co-editor of and contributor to the Field Guide for this field trip.

1989-1992. Chief of the IPGG project "Isotopic evolution of the Precambrian Lithosphere within the Aldan Shield, Baikal Region, and the Baltic Shield".  The Project was focused on combining U-Pb zircon ages of Precambrian igneous and metamorphic rocks with their Nd isotope characteristics in order to establish a sequence of the crust-forming and crust-reworking events in Precambrian of the Aldan Shield and Baikal region (Eastern Siberia), and of the Baltic Shield. 

1991-1992. PI in the IPGG project "Behavior of Radiogenic Isotopes under Different P-T-X Conditions". The project was devoted to the study of the radiogenic isotopes migration (U-Pb, Rb-Sr, Sm-Nd, and K-Ar systems) in zones developed at a contact of a basaltic dyke intrusion and host metamorphic rocks of variable mineralogy and chemical compositions. The project’s outcome was a better understanding of distances in the host rocks where thermal impulse and fluid migration caused disturbance of different isotope systems.

1991-1993. Co-chair of the Russian working group for the international project “Rapakivi Granites and Related Rocks”, UNESCO International Geological Correlation Program (IGCP) Project #315. Chiefs: I. Haapala (Finland) and R.F. Emslie (Canada). Responsible for organizing and conducting an international field trip to the Salmi granite-anorthosite batholith, Russian Karelia (1992). Co-author of the Field Guide for the trip. PI in conducting Pb-Sr-Nd isotope studies of Salmi batholith, Russian Karelia.

1991-1993. Chief of the Project “Pb-isotope Characteristics of the Gold Deposits from Siberian Craton” (Russian Foundation for Basic Research, Project #93-05-8006). Conducted a comparative Pb-isotope study of a large gold deposit Sukhoy Log, Bodaibo gold-bearing region, and a series of smaller gold deposits in Eastern Siberia.

1991-1993. Co-PI in a Project “The Role of Lower Crust in the Formation of Anorthosite-Rapakivi Granite Association”, George Soros Foundation, Grant ISF # RIE 000. Conducted Pb-Sr-Nd isotope studies of Ulkan Pluton, Eastern Siberia and Berdiaoush Pluton, South Urals region.

1971 -1985.  All Union Geological Research Institute, Leningrad (USSR Ministry of Geology). Engineer (1971-1981) and Junior Research Scientist (1981-1985).

 

PROFESSIONAL AFFILIATIONS

Member of the American Geophysical Union, Geological Society of America, the International Geochemistry Association, the Geochemical Society.

 

Conference Papers

  1. J.B. Paces, Z.E. Peterman, L.A. Neymark, J.F. Whelan, and B.D. Marshall, 1997, Geochronologic and isotope studies of calcite and silica constraining Quaternary unsaturated- and saturated zone hydrologic flux at Yucca Mountain, Nevada, USA. SEDE Workshop: “Use of hydrogeochemical information in testing groundwater flow models”, Borgholm, 1-3 September, 1997.
  2. L.A. Neymark, Yu.V. Amelin, J.B. Paces, Z.E. Peterman, 1998, U-Pb Age Evidence for long-term stability of the unsaturated Zone,  Yucca Mountain, Nevada, 1998 International High-Level Radioactive Waste Management Conference, May 11-14, Las Vegas, Nevada, p. 85-87.
  3. L.A. Neymark and Y.V. Amelin. 2000, Quaternary geochronology using combined U-Pb and U-series methods: the opal perspective. In: J.D. Woodhead, J.M. Hergt, W.P. Noble, Eds. Beyond 2000: New Frontiers in Isotope Geoscience, Lorne, Australia, 2000. Abstracts and Proceedings, p. 133-135.
  4. L.A. Neymark, Y.V. Amelin, J.B. Paces, J.F. Whelan, Z.E. Peterman, 2001. Age constraints on fluid inclusions in calcite at Yucca Mountain. International High-Level Radioactive Waste Management Conference, Las Vegas, Nevada, American Nuclear Society, CD ROM, unpaginated.
  5. J.F. Whelan, L.A. Neymark, E. Roedder, and R.J. Moscati, 2003. Thermochronology of secondary minerals from the Yucca Mountain unsaturated zone. Proceedings of 10th International High-Level Radioactive Waste Management Conference, Las Vegas, Nevada, American Nuclear Society, La Grange Park, p. 357-366.

Publications

  1. Yu.V.Amelin, E.Yu.Ritsk, L.A.Neymark, 1997, Geochronological and Nd-Sr-Pb isotopic study of the relationships between mafic magmatites and ultramafic tectonites in the Chaya massif, Baikal-Muya ophiolite belt. Earth and Planetary Science Letters, vol. 148, 299-316. (Provided U-Pb isotope data and 30 % of interpretations and text writing).
  2. L.A. Neymark, J.B. Paces, and Yu.V. Amelin, 1998, Neogene to Quaternary U-Th-Pb geochronology using opal, Yucca Mountain, Nevada, USA. Mineral. Mag., vol. 62A, 1077-1078.65            
  3. L.A. Neymark, J.B. Paces, B.D. Marshall, Z.E. Peterman, and J.F. Whelan, 2000, Hydrologic and geologic characteristics of the Yucca Mountain site relevant to the performance of a potential repository; Day 2, Beatty to Yucca Mountain; Stop 7B, Secondary minerals and paleohydrologic implications. GSA Field Guide, vol.2, p. 401-402.79           
  4. B.D. Marshall, L.A. Neymark, and Z.E. Peterman. 2005. Reply to Commentary: Assessment of past infiltration fluxes through Yucca Mountain on the basis of the secondary mineral record—is it a viable methodology? By Y.V. Dublyansky and S.Z. Smirnov. Journal of Contaminant Hydrology, vol. 7, 219– 224.