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Element Distribution Between Coexisting Authigenic Mineral Phases in Argillic and Zeolitic Altered Tephra, Olduvai Gorge, Tanzania

Published online by Cambridge University Press:  01 January 2024

Lindsay J. McHenry
Lindsay J. McHenry*
Affiliation:
Department of Geosciences, University of Wisconsin-Milwaukee, 3209 N. Maryland Ave, Milwaukee, WI 53211, USA
*
* E-mail address of corresponding author: lmchenry@uwm.edu
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Abstract

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The current study demonstrates how co-existing zeolite and clay minerals formed by the alteration of tephra in a closed-basin lacustrine and lake-margin environment can retain the overall composition of the original bulk tephra for many elements, even when diagenetic conditions and resulting authigenic mineral assemblages change. Zeolite and clay minerals co-exist in the closed-basin, saline-alkaline lacustrine altered tephra of Pleistocene Olduvai Gorge, Tanzania, and their diagenetic histories can be reconstructed using variations in their textures and compositions. The authigenic minerals in the altered tephra of the Olduvai paleolake form a classic ‘bull’s-eye’ pattern, with clay-dominated tephra in the distal lake margin, chabazite and phillipsite in the proximal margin, and phillipsite ± K-feldspar in the intermittently dry lake and lake center. Fifteen representative samples of altered volcanic ash lapilli (designated Tuff IF) were analyzed by X-ray diffraction (XRD), X-ray fluorescence (XRF), electron probe microanalysis (EPMA), and scanning electron microscopy (SEM) to determine their authigenic mineral assemblages and bulk compositions, and to texturally and compositionally compare their clay mineral and zeolite components.

Textural observations indicate that clay minerals formed first, followed by zeolites and finally feldspars. Clay minerals, however, persist even in the most altered samples. The overall composition of Tuff IF shows only limited change in Fe, Si, Al, and Na between fresh, clay-altered, and zeolite-dominated diagenetic environments, despite significant differences in authigenic assemblage. Where zeolites dominate the assemblage, the remaining clay minerals are rich in Mg, Fe, and Ti, elements that are not readily incorporated in zeolite structures. Where clay minerals dominate, they are more Al-rich. A ‘mixing model’ combining clay-mineral and zeolite compositions yields a close approximation of the original volcanic glass for most elements (exceptions including Mg, Ca, and K). This initial composition was preserved in part by the redistribution of elements between co-existing clay minerals and zeolites.

Keywords

ClayDiagenesisElement PartitioningOlduvai GorgePhillipsiteSaline-alkaline LakeSmectiteTephraZeolite
Type
Article
Information
Clays and Clay Minerals , Volume 58 , Issue 5 , October 2010 , pp. 627 - 643
Copyright
Copyright © Clay Minerals Society 2010

References

Boles, J.R. and Coombs, D.S., 1975 Mineral reactions in zeolitic Triassic tuff, Hokonui Hills, New Zealand Bulletin of the Geological Society of America 86 163–173 10.1130/0016-7606(1975)86<163:MRIZTT>2.0.CO;2.2.0.CO;2>CrossRefGoogle Scholar
Broxton, D.E., Bish, D.L. and Warren, R.G., 1987 Distribution and chemistry of diagenetic minerals at Yucca Mountain, Nye County, Nevada Clays and Clay Minerals 35 89–110 10.1346/CCMN.1987.0350202.CrossRefGoogle Scholar
Chipera, S.J., Apps, J.A., Bish, D.L., and Ming, D.W., 2001 Geochemical stability of natural zeolites Natural Zeolites: Occurrence, Properties, Applications Washington, D.C Mineralogical Society of America 117–161 10.1515/9781501509117-005.CrossRefGoogle Scholar
Chipera, S.J., Goff, F., Goff, C.J. and Fittipaldo, M., 2008 Zeolitization of intercaldera sediments and rhyolitic rocks in the 1.25 Ma lake of Valles caldera, New Mexico, USA Journal of Volcanology and Geothermal Research 178 317–330 10.1016/j.jvolgeores.2008.06.032.CrossRefGoogle Scholar
Deocampo, D.M., 2004 Authigenic clays in East Africa: Regional trends and paleolimnology at the Plio-Pleistocene boundary, Olduvai Gorge, Tanzania Journal of Paleolimnology 31 1–9 10.1023/B:JOPL.0000013353.86120.9b.CrossRefGoogle Scholar
Deocampo, D.M., Blumenschine, R.J. and Ashley, G.M., 2002 Wetland diagenesis and traces of early hominids, Olduvai Gorge, Tanzania Quaternary Research 57 1–11 10.1006/qres.2001.2317.CrossRefGoogle Scholar
Dibble, W.E. Jr. and Tiller, W.A., 1981 Kinetic model of zeolite paragenesis in tuffaceous sediments Clays and Clay Minerals 29 323–330 10.1346/CCMN.1981.0290502.CrossRefGoogle Scholar
Donovan, J., 2000 Probe for Windows: Analysis and Automation for EPMA, version 5.11 .Google Scholar
Drief, A. and Schiffman, P., 2004 Very low temperature alteration of sideromelane in hyaloclastites and hyalotuffs fromKilauea and Mauna Kea volcanoes: implications for the mechanism of palagonite formation Clays and Clay Minerals 52 622–634 10.1346/CCMN.2004.0520508.Google Scholar
Franzson, H., Zierenberg, R. and Schiffman, P., 2008 Chemical transport in geothermal systems in Iceland. Evidence fromhydrothermal alteration Journal of Volcanology and Geothermal Research 173 217–229 10.1016/j.jvolgeores.2008.01.027.CrossRefGoogle Scholar
Grant, J.A., 1986 The isocon diagram — a simple solution to Gresens’ equation for metasomatic alteration Economic Geology 81 1976–1982 10.2113/gsecongeo.81.8.1976.CrossRefGoogle Scholar
Grant, J.A., 2005 Isocon analysis: A brief review of the method and applications Physics and Chemistry of the Earth 30 997–1004 10.1016/j.pce.2004.11.003.CrossRefGoogle Scholar
Hay, R.L., 1963 Zeolitic weathering in Olduvai Gorge, Tanganyika Geological Society of America Bulletin 74 1281–1286 10.1130/0016-7606(1963)74[1281:ZWIOGT]2.0.CO;2.CrossRefGoogle Scholar
Hay, R.L., 1964 Phillipsite of saline lakes and soils American Mineralogist 49 1366–1387.Google Scholar
Hay, R.L., 1966 Zeolites and Zeolitic Reactions in Sedimentary Rocks New York Geological Society of America 10.1130/SPE85-p1.CrossRefGoogle Scholar
Hay, R.L., 1970 Silicate reactions in three lithofacies of a semi-arid basin, Olduvai Gorge, Tanzania 3 237–255.Google Scholar
Hay, R.L., 1973 Lithofacies and environments of Bed I, Olduvai Gorge, Tanzania Quaternary Research 3 541–560 10.1016/0033-5894(73)90030-6.CrossRefGoogle Scholar
Hay, R.L., 1976 Geology of the Olduvai Gorge: A Study of Sedimentation in a Semiarid Basin Berkeley, California, USA University of California Press.CrossRefGoogle Scholar
Hay, R.L. (1980) Zeolitic weathering of tuffs in Olduvai Gorge, Tanzania. Pp. 155–163 in: Proceedings of the Fifth International Conference on Zeolites: Naples, Italy, 1–6 June 1980 (and Rees, L.V.C., editor). Heyden, London.Google Scholar
Hay, R.L., 1986 Geologic occurrence of zeolites and some associated minerals Pure and Applied Chemistry 58 1339–1342 10.1351/pac198658101339.CrossRefGoogle Scholar
Hay, R.L., 1996 Stratigraphy and Lake-margin Paleoenvironments of Lowermost Bed II in Olduvai Gorge Kaupia-Darmstädter Beiträge zur Naturgeschichte 6 223–230.Google Scholar
Hay, R.L. and Guldman, S.G., 1987 Diagenetic alteration of silicic ash in Searles Lake, California Clays and Clay Minerals 35 449–457 10.1346/CCMN.1987.0350605.CrossRefGoogle Scholar
Hay, R.L. and Kyser, T.K., 2001 Chemical sedimentology and paleoenvironmental history of Lake Olduvai, a Pliocene lake in northern Tanzania Geological Society of America Bulletin 113 1505–1521 10.1130/0016-7606(2001)113<1505:CSAPHO>2.0.CO;2.2.0.CO;2>CrossRefGoogle Scholar
Hay, R.L., Sheppard, R.A., Bish, D.L., and Ming, D.W., 2001 Occurrences of zeolites in sedimentary rocks: an overview Natural Zeolites: Occurrence, Properties, Applications Washington, D.C Mineralogical Society of America 216–234.Google Scholar
Hover, V.C. and Ashley, G.M., 2003 Geochemical signatures of paleodepositional and diagenetic environments: A STEM/ AEM study of authigenic clay minerals from an arid rift basin, Olduvai Gorge, Tanzania Clays and Clay Minerals 51 231–251 10.1346/CCMN.2003.0510301.CrossRefGoogle Scholar
Jones, B.F. and Deocampo, D.M., 2003 Geochemistry of Saline Lakes Surface and Ground Water, Weathering, Erosion, and Soils 5 393–424.Google Scholar
Jones, B.F. and Weir, A.H., 1983 Clay minerals of Lake Albert, an alkaline, saline lake Clays and Clay Minerals 34 161–172 10.1346/CCMN.1983.0310301.CrossRefGoogle Scholar
Langella, A., Cappelletti, P., de’Gennaro, M., Bish, D.L., and Ming, D.W., 2001 Zeolites in closed hydrologic systems Natural Zeolites: Occurrence, Properties, Applications Washington, D.C. Mineralogical Society of America 235–260 10.1515/9781501509117-009.CrossRefGoogle Scholar
McHenry, L.J., 2004 Characterization and correlation of altered Plio-Pleistocene tephra using a “multiple technique” approach: Case study at Olduvai Gorge, Tanzania New Jersey, USA Rutgers University, New Brunswick.Google Scholar
McHenry, L.J., 2005 Phenocryst composition as a tool for correlating fresh and altered tephra, Bed I, Olduvai Gorge, Tanzania Stratigraphy 2 101–115.CrossRefGoogle Scholar
McHenry, L.J., 2009 Element mobility during zeolitic and argillic alteration of volcanic ash in a closed-basin lacustrine environment: Case study Olduvai Gorge, Tanzania Chemical Geology 265 540–552 10.1016/j.chemgeo.2009.05.019.CrossRefGoogle Scholar
McHenry, L.J. (in press) A revised stratigraphic framework for Olduvai Gorge Bed I based on tuff geochemistry. Journal of Human Evolution.Google Scholar
McHenry, L.J., Mollel, G.M. and Swisher, C.C. III, 2008 Compositional and textural correlations between Olduvai Gorge Bed I tephra and volcanic sources in the Ngorongoro Volcanic Highlands, Tanzania Quaternary International 178 306–319 10.1016/j.quaint.2007.01.004.CrossRefGoogle Scholar
Mees, F., Stoops, G., Van Ranst, E., Paepe, R. and Van Overloop, E., 2005 The nature of zeolite occurrences in deposits of the Olduvai Basin, Northern Tanzania Clays and Clay Minerals 53 659–673 10.1346/CCMN.2005.0530612.CrossRefGoogle Scholar
Mees, F., Segers, S. and Van Ranst, E., 2007 Palaeoenvironmental significance of the clay mineral composition of Olduvai basin deposits, northern Tanzania Journal of African Earth Sciences 47 39–48 10.1016/j.jafrearsci.2006.11.003.CrossRefGoogle Scholar
Ming, D.W. and Mumpton, F.A., 1989 Zeolites in soils Minerals in Soil Environments 837–911.Google Scholar
Moore, D.M. and Reynolds, R.C. Jr., 1997 X-ray Diffraction and the Identification and Analysis of Clay Minerals 2 Oxford, UK Oxford University Press.Google Scholar
Passaglia, E., 1970 The crystal chemistry of chabazites American Mineralogist 55 1278–1301.Google Scholar
Pe-Piper, G. and Tsolis-Katagas, P., 1991 K-rich mordenite fromLate Miocene rhyolitic tuffs, island of Samos, Greece Clays and Clay Minerals 39 239–247 10.1346/CCMN.1991.0390303.CrossRefGoogle Scholar
Renaut, R.W., 1993 Zeolitic diagenesis of late Quaternary fluviolacustrine sediments and associated calcrete formation in the Lake Bogoria Basin, Kenya Rift Valley Sedimentology 40 271–301 10.1111/j.1365-3091.1993.tb01764.x.CrossRefGoogle Scholar
Sheppard, R.A., Gude, A.J., and Fitzpatrick, J.J. (1988) Distribution, characterization, and genesis of mordenite in Miocene silicic tuffs at Yucca Mountain, Nye County, Nevada. U.S. Geological Survey Bulletin, 1777, 22 pp.Google Scholar
Sheppard, R.A., Hay, R.L., Bish, D.L., and Ming, D.W., 2001 Formation of zeolites in open hydrologic systems Natural Zeolites: Occurrence, Properties, Applications Washington, D.C. Mineralogical Society of America 261–275 10.1515/9781501509117-010.CrossRefGoogle Scholar
Snellings, R., Van Haren, T., Machiels, L., Mertens, G., Vandenberghe, N. and Elsen, J., 2008 Mineralogy, geochemistry, and diagenesis of clinoptilolite tuffs (Miocene) in the central Simav graben, western Turkey Clays and Clay Minerals 56 622–632 10.1346/CCMN.2008.0560603.CrossRefGoogle Scholar
Stollhofen, H., Stanistreet, I.G., McHenry, L.J., Mollel, G.F., Blumenschine, R.J. and Masao, F.T., 2008 Fingerprinting facies of the Tuff IF marker, catastrophe for early hominin palaeoecology, Olduvai Gorge, Tanzania Palaeogeography, Palaeoclimatology, Palaeoecology 259 382–409 10.1016/j.palaeo.2007.09.024.CrossRefGoogle Scholar
Surdam, R.C. and Eugster, H.P., 1976 Mineral reactions in the sedimentary deposits of the Lake Magadi region, Kenya Geological Society of America Bulletin 87 1739–1752 10.1130/0016-7606(1976)87<1739:MRITSD>2.0.CO;2.2.0.CO;2>CrossRefGoogle Scholar
Taylor, M.W. and Surdam, R.C., 1981 Zeolite reactions in the tuffaceous sediments at Teels Marsh, Nevada Clays and Clay Minerals 29 341–352 10.1346/CCMN.1981.0290504.CrossRefGoogle Scholar