Konter's isotope geochemistry group






 
Personnel
Dr. Jasper Konter
Volcanology, Geochemistry, Petrology division
Department of Geology and Geophysics
SOEST, University of Hawaii, Manoa


RESEARCH INTERESTS


Dr. Jasper Konter is interested in mantle geochemistry, magmatic processes and volcanology. His research group focuses on the use of Pb, Sr, Nd, Hf, and Fe isotopes , as well as major and trace element abundances.

Konter's group works in the SOEST isotope lab and SOEST MC-ICP-MS lab


TEACHING


I teach/taught the following courses:
Trace Elements and Isotopes (UH GG711)
Igneous/Metamorphic Petrology (UTEP GEOL3315)
Introductory Geology for non-majors (UTEP GEOL1312)
Isotope Geology (UTEP GEOL5343)
Volcanology (UTEP GEOL4315/5315/6315)
Tectonics and Metamorphism (UTEP GEOL5315)


STUDENTS


(current): Valerie Finlayson (UH PhD program)

(past): Lisa Anaya (Dept. Homeland Security, UTEP MSc program), Bradley Benavides (Industry, UTEP MSc program), Lynnette Crocker (Industry, UTEP MSc program), Lauren Storm (Industry, UTEP MSc program)

(past undergraduate): Lisa Anaya (Dept. Homeland Security, UTEP MSc program), Jacqueline Engel (UTEP MSc program), Christine Waters (UH PhD program), Hector Zamora (U Arizona, PhD program)


 
Instruments
We currently have access to several mass spectrometers and a clean room complex (we are part of the SOEST isotope lab and SOEST MC-ICP-MS lab ), including:

* a multi-collector ICP-MS ( SOEST MC-ICP-MS Nu Plasma),
* a multi-collector TIMS ( SOEST Isotope Lab VG Sector)
* a multi-collector TIMS ( SOEST Isotope Lab Micromass Sector 54)

An array of other equipment is available within the school: Research facilities at G&G-SOEST.)


 
Labs
In support of these instruments, the department has a range of laboratory facilities:

* a clean room with class 100 environment for separation/purification of Sr, Nd, Pb, Hf, Fe, Th, U, Ra, Pa, Ba, Rb, Sm, Li and Po. This clean room has multiple dedicated fume hoods and hepa-filtered laminar flow exhausting hoods (and HEPA-filtered drying tunnels)
* Millipore 18 MOhm water purification systems
* Besides multiple quartz-glass sub-boiling stills used for water and acid distillation, we also have 2 Savillex double distilling setups the DST-1000 (2 connected units)
and the "classic" Savillex design (2 connected units)
* array of lab tools for sample digestions, separations, evaporation of strong acids and other requirements for isotope analyses

We have designed our own hotplates and heat controllers for hotplates and stills. For questions about heat-controller design email Jasper (click on my name above for info)



 
Project Updates


Konter's group has been working on multiple projects over the last few years, including both sample analysis of natural samples, and method development

Update 2013. Dr. Konter's team worked on several projects this year: the major project this year was an NSF-OCE funded cruise on R/V Roger Revelle (ship track below), sampling the Tuvalu, Wallis/Futuna, Samoa, Fiji, Tonga volcanoes on our proposed Rurutu hotspot trail.


In addition, further data were collected on Savaii samples, and Fe isotope analyses were performed on a range of samples. Several projects are in various stages of manuscripts (Line Islands, Rio Grande Rift lavas, Hf column separation, Sr by MC-ICP-MS, Fe isotope data from multiple igneous settings and technique paper for Nu Plasma HR). In addition to the isotope projects, Konter's student Benavides worked with EPMA and ICP-OES to obtain major element compositions on mantle xenoliths. ICP-OES data improved Ca precision (used for geobarometry) by a factor of 10 compared to EPMA. Finally, the cruise also included a test of Laser Induced Breakdown Spectroscopy (LIBS) of dredge samples. This resulted in characterization of more than 600 samples, and technique development of this system continues.

Update Winter 2012. Dr. Konter's team has worked on radiogenic isotopes in volcanic systems of the Samoa, Line, and Tuvalu Islands, the Southern Rio Grande Rift, and is working on an updated double spike Fe technique to obtain errors <0.05 permil. Furthermore, work has started to trace atmospheric dust with radiogenic isotope compositions (collaboration with Dr. Gill). See also Publications.

Continued work on samples from the Samoan Island of Savaii have led to an estimate of the volume of rejuvenated volcanism in Samoa. Samples from the bottom of Sinaloa waterfall show that at least 200m of rejuvenated lavas cover this area of the volcano. Together with Matt Jackson (BU) we have carried out a detailed comparison with Hawaiian rejuvenated volcanism (in review G-cubed). We are also continuing our work on the shield lavas from Savaii (also with Anthony Koppers, OSU).

Lauren Storm (MSc) has carried out a detailed analysis of recently Ar-dated samples (collaboration with Koppers, OSU)from the Line Islands (radiogenic isotopes). She presented her results at Fall AGU 2011, detailing an unlikely origin for this volcanic chain from "standard" hotspot volcanism.

Through combined efforts, Konter and Jackson (BU) have obtained rare dredge samples from the Tuvalu Islands, to test the existence of the potential trace of the Rurutu hotspot through the Samoan Islands and continuing in the Tuvalu Islands. The limited samples confirm the expected HIMU composition of the Rurutu hotspot, suggesting a third Hawaii-Emperor type bend may exist where Samoa and Tuvalu meet. These results were part of presentations at 2011 Goldschmidt and Fall AGU, and Konter, Jackson and Koppers are now recommended for funding (NSF-OCE) for a 30 day dredging cruise, to extensively sample this area.



Follow-up work on the thesis by L. Crocker (2010) has revealed that the Potrillo Volcanic Field and the nearby Hillsboro volcanic field define two separate data trends/clusters. Integrated major, trace element (collaboration with Tyrone Rooney, MSU) and Sr-Pb isotope data are consistent with two distinct mixing trends roughly originate from the same isotopic composition. Results were presented at AGU and we anticipate this work will be submitted in the next few months. Some of the data have also been used for an NSF proposal (EAR).

Work on double spike Fe isotopes and atmospheric dust have only just commenced and the first meeting presentations are expected this year. Initial results from the Fe isotope work (Valerie Finlayson, PhD student) suggest potential to improve precision to +/- 0.03 permil.


Update Summer 2010. Dr. Konter's team has worked on mainly Pb isotope studies of several field areas, and method development for radiogenic isotope measurements.

Lynnette Crocker (MSc) succesfully defended her thesis on Rio Grande volcanic systems this summer, and presented at the annual Goldschmidt meeting. Her research investigates the Pb isotope compositions of lavas from several Rio Grande Rift fields (Potrillo, Hillsboro, Palomas, Elephant Butte). Combined with published data an argument can be made for both lower and upper crustal contamination of mantle melts. We are currently collecting trace element compositions for the samples to confirm the mixing relationships suggested by the isotope diagrams. The figure shows the trends of a number of Rio Grande Rift volcanic fields shown as colored boxes, and the tested mixing end-members involved. With the abundance data, the current manuscript will be revised and submitted to Lithos.

Konter recently presented new work at the Goldschmidt meeting on lavas collected from Savaii, Samoa. This work is funded by NSF, and together with Matt Jackson (BU) and Anthony Koppers (OSU), involves a strategic sampling expedition carried out in Fall 2009 into the deepest canyon of Savaii, followed by abundance, isotope, and age analysis. Good exposures around streams and waterfalls allowed for sampling of 2 sequences of lavas flows deep in the interior of the volcano. The first Pb isotope data suggests that the late stage (rejuvenated) lavas are thicker previously mapped by Kear and Wood (1959). As a result, a conservative estimate of the relative volume of erupted rejuvenated lavas is greater than 1%, while in Hawaiian volcanoes the largest relative volume is about 0.1% (Garcia et al., 2010). Once the other isotope data (Sr, Nd) have been collected, combined with ages and abundance data, we will place these lavas in the larger tectonic framework of the northern terminus of the Tonga Trench.

Evolved samples from Upolu and Savaii (part of Kear and Wood's "Fagaloa" series) define a trend between other Upola-Fagaloa lavas and rejuvenated lavas. This may be a sign of a slight change in composition toward the end of the shield stage, and potentially a small volume of post-shield volcanism.


ANALYTICAL CAPABILITIES OF THE NU PLASMA



Konter has also been working on technique setup and development both in a Class 100 Clean lab environment, and on the Nu Plasma HR. For radiogenic isotope measurements, samples from 1 digestion are first passed through Eichrom's Sr resin (shrink teflon columns) which allows for Sr and Pb separation. Pb is then cleaned up through Pb chemistry (HBr-HCl on AG1 resin; shrink teflon columns), while Sr is purified with another pass through Eichrom's Sr-resin. REEs are separated from the Sr-resin wash on Eichrom's LN-Spec (Savillex 15ml columns), and Hf with a primary column (Savillex 30 ml), followed by Eichrom's TODGA resin (shrink teflon columns).

Sr-Pb-Nd-Hf has been tested and produces the same results as the previous technique (technique and results in revision at Chemical Geology). We also developed an alternative Hf separation, but the TODGA approach ends up using less resin and acid.

Below follows the analytical capabilities of the HR Nu Plasma, as measured at UTEP

NU PLASMA STANDARD RESULTS

For Pb isotopes, the NBS 981 Pb standard average 206Pb/204Pb = 16.9435+/-0.0039, 207Pb/204Pb = 15.5003+/-0.0038, and 208Pb/204Pb = 36.7260+/-0.0102. Errors given as 2 standard deviations (not standard errors) of 74 runs. The current procedure uses Tl (NBS 997) doping.

For Nd isotopes, the JNdi-1 standard is used on a daily basis, but the more commonly used La Jolla standard averages 143Nd/144Nd = 0.511839 +/- 0.0000095 (N = 12). In one experiment, the La Jolla standard and the JNdi-1 standard were run alternating during two different analytical sessions. When corrected to the accepted value for La Jolla of 143Nd/144Nd = 0.511859, our JNdi-1 standard averages 0.512116 +/- 0.0000098. We also tested static versus dynamic run performance. A triple dynamic program collecting 3 x 20 ratios generates smaller variations within analytical sessions. For static analysis, daily session errors (2 standard deviations) range from 6e-6 to 9e-6, while dynamic runs show 2e-6 to 7e-6. Over several analytical sessions this results in an error of 9.8e-6 for the static routine, while the dynamic routine has 2 sigma of 6.7e-6, mainly this high due to 1 day with a higher daily variation.

For Sr isotopes, the NBS 987 Sr standard is used on a dialy basis. We have found that an internal correction for Kr interference on 86Sr yields more precise data than an on-peak-zeroes subtraction. The UTEP Sr routine is a double dynamic program that uses 84Kr for the Kr correction on 86Kr, after deconvolving the 84Sr intensity. In addition, the common (85/87)Rb interference correction is employed. As a result, a daily external precision of 1.1e-5 is achieved (n about 7). Day to day shifts in the average make the long-term precision closer to 3e-5 (while each day stays within 1.1e-5): The 987 standard averages 0.71030 +/- 0.00003 for multi-session average. This method is in revision as a paper at Chemical Geology.

For Hf isotopes, an Alfa Aesar Hf ICP standard (14374) is used on a daily basis, but the commonly used JMC 475 standard averaged 176Hf/177Hf = 0.282154 +/- 0.000004 (N = 8). In an experiment running both JMC 475 and Alfa 14374 in one day, the JMC 475 value reported was obtained, while the Alfa 14374 standard averaged 0.282219 +/- 0.000007 (N = 10). Our static routine incorporates a correction for 176Lu (through 175) and 176Yb (through 173), as well as Ta and W for interference on 180Hf.

 

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