Janet Margaret Hergt is an Australian geochemist. She is a Redmond Barry Distinguished Professor in the School of Earth Sciences at the University of Melbourne, Victoria, Australia. The main focus of her research has been in the chemical analysis of rocks and minerals to explore the exquisite record of Earth processes preserved within them. Hergt is best known for her geochemical investigations of magmatic rocks although she has employed similar techniques in interdisciplinary projects including areas of archaeological and biological science.
Early life and education
Hergt's earliest years were spent living on dairy farms in rural Victoria before moving to Frankston where she attended Karingal Primary School, and later Karingal High School. Hergt completed her undergraduate degree (BScHons) at La Trobe University in Melbourne in 1983, where she was awarded the David Myers University Medal and Ian Carlyle Medal in Geology. She received an Australian Government scholarship to study at the Australian National University in Canberra where she completed her PhD under the joint supervision of Bruce Chappell and Ian McDougall. Her project involved the analysis of compositionally unusual continental flood basalts (magmatism on a vast scale often occurring as a precursor to continental breakup) from the Ferrar Province and her thesis is entitled 'The Origin and Evolution of the Tasmanian Dolerites'. It was during this time that she learned to appreciate the power of trace element and isotopic data retrieved from magmatic rocks.
Career and impact
Throughout her career, Hergt has retained a keen interest in extracting high quality geochemical data from rocks and minerals to solve problems in the geosciences. Her work on the Tasmanian Dolerites provided arguably the first dataset that combined major element, trace element, Sr-, Nd-, Pb- and oxygen isotope data on the same samples from a single suite of flood basalts. The dataset for the Tasmanian Dolerites, together with the extreme compositions of these rocks, provided the first opportunity to test competing hypotheses about source processes and constrain the origin of these magmas.
Hergt secured her first post-doctoral research position in the UK in 1988 working at the Open University with Chris Hawkesworth on a range of topics including further work on flood basalt magmatism (in Antarctica, Brazil and Siberia) with a number of Australian and international colleagues. It was at the Open University that she also began her studies into the geochemical expression of arc rupture and back-arc basin opening in the Lau Basin in the Southwest Pacific. Hergt participated on Integrated Ocean Drilling Program (IODP) Leg 135, identifying two mantle domains with geochemical characteristics of "Indian" or "Pacific" mid-ocean ridge basalts that has aided in understanding the mantle dynamics in this region. Other work from the IODP expedition demonstrated that magmas erupted at the earliest stages of arc rupture had the ability to tap mantle sources as well as source rocks modified by the flux of elements released from the subducting slab.
Following her move to the University of Melbourne in 1994, Hergt's contributions have involved a wide range of international collaborators and graduate students, and have included investigations of continental flood basalts, arc magmas, granite formation, ore deposits, the origin of kimberlites and processes preserved in mantle xenoliths. Hergt has also made important contributions in establishing innovative laboratory protocols and has supported the development of Iolite data visualisation software since its inception. Most recently, her work has extended to applications of geochemistry in the biosciences and archaeological science.
Hergt has held a variety of senior leadership roles at the University of Melbourne, including Deputy Head of the School of Earth Sciences (2001-2004), Associate Dean-Academic Programs in the Faculty of Science (2001–2003), Head of the School of Earth Sciences (2005–2013), Deputy Dean of the Faculty of Science (2011–2013 & 2014–2017), Acting Dean of the Faculty of Science (2013–2014), Deputy Vice President then Vice President of Academic Board (2018–2019) and President of Academic Board (2020–current). Hergt became a Vincent Fairfax Fellow in 2018 and was recognised as a Redmond Barry Distinguished Professor in 2019.
Hergt has served on a wide range of Advisory Boards, Senior Committees, Review Panels, and the Editorial Boards of several international journals (Chemical Geology 2008–2016, Geostandards and Geoanalytical Research 2000–2013; Journal of the Geological Society of London, 2002–2007). In 2021 the Geochemical Society (USA) and the European Association of Geochemistry awarded her the honorary title of Geochemistry Fellow for her contributions to the field of geochemistry.
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- HERGT, J. M.; CHAPPELL, B. W.; McCULLOCH, M. T.; McDOUGALL, I.; CHIVAS, A. R. (1989-08-01). "Geochemical and Isotopic Constraints on the Origin of the Jurassic Dolerites of Tasmania". Journal of Petrology. 30 (4): 841–883. doi:10.1093/petrology/30.4.841. ISSN 0022-3530.
- Hergt, J.M.; Peate, D.W.; Hawkesworth, C.J. (July 1991). "The petrogenesis of Mesozoic Gondwana low-Ti flood basalts". Earth and Planetary Science Letters. 105 (1–3): 134–148. doi:10.1016/0012-821x(91)90126-3. ISSN 0012-821X.
- Lightfoot, P. C.; Hawkesworth, C. J.; Hergt, J.; Naldrett, A. J.; Gorbachev, N. S.; Fedorenko, V. A.; Doherty, W. (June 1993). "Remobilisation of the continental lithosphere by a mantle plume: major-, trace-element, and Sr-, Nd-, and Pb-isotope evidence from picritic and tholeiitic lavas of the Noril'sk District, Siberian Trap, Russia". Contributions to Mineralogy and Petrology. 114 (2): 171–188. doi:10.1007/bf00307754. ISSN 0010-7999.
- Hergt, J.M.; Hawkesworth, C.J. (May 1994), "Pb-, Sr-, and Nd-Isotopic Evolution of the Lau Basin: Implications for Mantle Dynamics during Backarc Opening", Proceedings of the Ocean Drilling Program, 135 Scientific Results, Ocean Drilling Program, retrieved 2021-03-30
- Hergt, J.M.; Farley, K.N. (May 1994), "Major Element, Trace Element, and Isotope (Pb, Sr, and Nd) Variations in Site 834 Basalts: Implications for the Initiation of Backarc Opening", Proceedings of the Ocean Drilling Program, 135 Scientific Results, Ocean Drilling Program, retrieved 2021-03-30
- BRAUNS, C. M.; HERGT, J. M.; WOODHEAD, J. D.; MAAS, R. (2000-07-01). "Os Isotopes and the Origin of the Tasmanian Dolerites". Journal of Petrology. 41 (7): 905–918. doi:10.1093/petrology/41.7.905. ISSN 1460-2415.
- Hergt, Janet M.; Woodhead, Jon D. (October 2007). "A critical evaluation of recent models for Lau–Tonga arc–backarc basin magmatic evolution". Chemical Geology. 245 (1–2): 9–44. doi:10.1016/j.chemgeo.2007.07.022. ISSN 0009-2541.
- Woodhead, J.D.; Hergt, J.M.; Davidson, J.P.; Eggins, S.M. (October 2001). "Hafnium isotope evidence for 'conservative' element mobility during subduction zone processes". Earth and Planetary Science Letters. 192 (3): 331–346. doi:10.1016/s0012-821x(01)00453-8. ISSN 0012-821X.
- Hergt, J; Woodhead, J; Schofield, A (August 2007). "A-type magmatism in the Western Lachlan Fold Belt? A study of granites and rhyolites from the Grampians region, Western Victoria". Lithos. 97 (1–2): 122–139. doi:10.1016/j.lithos.2006.12.008. ISSN 0024-4937.
- Iles, Kieran A.; Hergt, Janet M.; Woodhead, Jon D.; Ickert, Ryan B.; Williams, Ian S. (March 2020). "Petrogenesis of granitoids from the Lachlan Fold Belt, southeastern Australia: The role of disequilibrium melting". Gondwana Research. 79: 87–109. doi:10.1016/j.gr.2019.08.011. ISSN 1342-937X.
- Paton, Chad; Hergt, Janet M.; Woodhead, Jon D.; Phillips, David; Shee, Simon R. (November 2009). "Identifying the asthenospheric component of kimberlite magmas from the Dharwar Craton, India". Lithos. 112: 296–310. doi:10.1016/j.lithos.2009.03.019. ISSN 0024-4937.
- Woodhead, Jon; Hergt, Janet; Phillips, Dave; Paton, Chad (November 2009). "African kimberlites revisited: In situ Sr-isotope analysis of groundmass perovskite". Lithos. 112: 311–317. doi:10.1016/j.lithos.2009.03.031. ISSN 0024-4937.
- Dalton, Hayden; Giuliani, Andrea; O'Brien, Hugh; Phillips, David; Hergt, Janet (October 2020). "Corrigendum to "The role of lithospheric heterogeneity on the composition of kimberlite magmas from a single field: The case of Kaavi-Kuopio, Finland" [Lithos 354–355 (2020) 105333]". Lithos. 370–371: 105611. doi:10.1016/j.lithos.2020.105611. ISSN 0024-4937.
- Chappell, Bruce W.; Hergt, Janet M. (December 1989). "The use of known Fe content as a flux monitor in neutron activation analysis". Chemical Geology. 78 (2): 151–158. doi:10.1016/0009-2541(89)90113-7. ISSN 0009-2541.
- Woodhead, Jon D; Hergt, Janet M (June 1997). "Application of the `double spike' technique to Pb-isotope geochronology". Chemical Geology. 138 (3–4): 311–321. doi:10.1016/s0009-2541(97)00013-2. ISSN 0009-2541.
- Woodhead, Jon D.; Hergt, Janet M. (July 2005). "A Preliminary Appraisal of Seven Natural Zircon Reference Materials for In Situ Hf Isotope Determination". Geostandards and Geoanalytical Research. 29 (2): 183–195. doi:10.1111/j.1751-908x.2005.tb00891.x. ISSN 0150-5505.
- Woodhead, Jon; Swearer, Stephen; Hergt, Janet; Maas, Roland (2005). "In situ Sr-isotope analysis of carbonates by LA-MC-ICP-MS: interference corrections, high spatial resolution and an example from otolith studies". Journal of Analytical Atomic Spectrometry. 20 (1): 22. doi:10.1039/b412730g. ISSN 0267-9477.
- Paton, Chad; Woodhead, Jon D.; Hergt, Janet M.; Phillips, David; Shee, Simon (2007-11-16). "Strontium Isotope Analysis of Kimberlitic Groundmass Perovskite via LA-MC-ICP-MS". Geostandards and Geoanalytical Research. 0 (0): 071117031212001–???. doi:10.1111/j.1751-908x.2007.00131.x. ISSN 0150-5505.
- Iles, Kieran A.; Hergt, Janet M.; Sircombe, Keith N.; Woodhead, Jon D.; Bodorkos, Simon; Williams, Ian S. (May 2015). "Portrait of a reference material: Zircon production in the Middledale Gabbroic Diorite, Australia, and its implications for the TEMORA standard". Chemical Geology. 402: 140–152. doi:10.1016/j.chemgeo.2015.02.036. ISSN 0009-2541.
- Paton, Chad; Hellstrom, John; Paul, Bence; Woodhead, Jon; Hergt, Janet (2011). "Iolite: Freeware for the visualisation and processing of mass spectrometric data". Journal of Analytical Atomic Spectrometry. 26 (12): 2508. doi:10.1039/c1ja10172b. ISSN 0267-9477.
- Paul, Bence; Paton, Chad; Norris, Ashley; Woodhead, Jon; Hellstrom, John; Hergt, Janet; Greig, Alan (2012). "CellSpace: A module for creating spatially registered laser ablation images within the Iolite freeware environment". Journal of Analytical Atomic Spectrometry. 27 (4): 700. doi:10.1039/c2ja10383d. ISSN 0267-9477.
- Marillo-Sialer, Estephany; Black, Jay R.; Paul, Bence; Kysenius, Kai; Crouch, Peter J.; Hergt, Janet M.; Woodhead, Jon D.; Hare, Dominic J. (2020). "Construction of 3D native elemental maps for large biological specimens using LA-ICP-MS coupled with X-ray tomography". Journal of Analytical Atomic Spectrometry. 35 (4): 671–678. doi:10.1039/c9ja00423h. ISSN 0267-9477.
- Finch, Damien; Gleadow, Andrew; Hergt, Janet; Levchenko, Vladimir A.; Fink, David (April 2019). "New developments in the radiocarbon dating of mud wasp nests". Quaternary Geochronology. 51: 140–154. doi:10.1016/j.quageo.2019.02.007. ISSN 1871-1014.
- Finch, Damien; Gleadow, Andrew; Hergt, Janet; Levchenko, Vladimir A.; Heaney, Pauline; Veth, Peter; Harper, Sam; Ouzman, Sven; Myers, Cecilia; Green, Helen (February 2020). "12,000-Year-old Aboriginal rock art from the Kimberley region, Western Australia". Science Advances. 6 (6): eaay3922. doi:10.1126/sciadv.aay3922. ISSN 2375-2548.
- Finch, Damien; Gleadow, Andrew; Hergt, Janet; Heaney, Pauline; Green, Helen; Myers, Cecilia; Veth, Peter; Harper, Sam; Ouzman, Sven; Levchenko, Vladimir A. (March 2021). "Ages for Australia's oldest rock paintings". Nature Human Behaviour. 5 (3): 310–318. doi:10.1038/s41562-020-01041-0. ISSN 2397-3374.