Numerous discoveries of natural ikaite have been made since 1963. Cataloged here are some of the more significant reported finds. These discoveries are suggesting that ikaite has two general modes of occurrence. The first is as free growing ikaite crystals that sprouts from an attachment site and grows into a water filled space and, if circumstances allow, into columns. The second, and perhaps the most common mode, is as individual crystals, or small clusters, growing displacively in organic-rich muds.
The first mode of occurence for ikaite is ikaite free-growing into solution. Ikaite growing in this way has the ability to form structures that can reach spectacular proportions. This is the mode of occurence of ikaite in the type locality for the mineral in Ikka Fjord, SW Greenland.
In Ikka Fjord ikaite precipitation from a reaction between the water from submarine springs and seawater has led to the development of hundreds of ikaite tufa columns, some of which which reach heights of up to 20m. Ikka Fjord and its beautiful ikaite 'Column Garden' has become the focus of research for a multi-national, multi-disciplined group of scientists of The Ikka Project working from a common base at The Geological Institute, The University of Copenhagen. In Ikka fjord ikaite precipitation is favoured by an ideal spring chemistry and the physical conditions in the fjord. The ikaite precipitates from springs rich in bicarbonate ions reacting with calcium ions from the seawater that fills the fjord (Buchardt, et al. 1997). Calcite, the normal calcium carbonate mineral expected to form in such a geological system, is inhibited from forming by the levels of phosphate present in the springs and the cold water environment of the fjord make conditions favourable for ikaite precipitation. The submarine spring system is connected to a carbonatite intrusion that straddles the fjord and it is the passage of the groundwater through this complex that enriches it in the bicarbonate ions and phosphate required for ikaite formation. This relationship is clearly demonstrated by the fact that in Ikka fjord ikaite columns are only found within the outcrop of the intrusive complex.
Around the shores of Mono Lake, eastern California, bizarre tufa towers, up to several metres high, are found forming a striking feature of the area popular with tourists. These towers situated over springs are presently formed from calcium carbonate but recent work is suggesting that this is a secondary mineral and that the primary precipitate might in fact be ikaite (Bischoff et al., 1993; Council & Bennett, 1993). This suggestion has followed the discoveries that ikaite does actually precipitate around springs associated with the tufas in Mono Lake during the frigid winter months (Bischoff et al., 1993; Council & Bennett, 1993).
In the semidesert country of the western Great Basin of the United States other impressive calcareous tufas are found forming mounds and towers reaching tens of metres in height (King, 1878; Russell, 1883 & 1889; Dana, 1884). It has been suggested that these too were originally deposited as ikaite (Shearman et al.1989) a new idea that has initiated a number of scientists to investigate the present and past environments and chemistry of Mono Lake and Pyramid Lake (the modern remnant of the large Quaternary lake, Lake Lahonton). If it can be shown that ikaite was the original mineral that formed these tufas then the Lake Lahonton tufa mounds are possibly the most spectacular and abundant ikaite deposit ever developed.
Details about the tufa columns of Mono Lake together with some spectacular photographs can be found at the Web page of The Mono Lake Committee.
Ito (1996) reported finding ikaite during the winter months forming in ice and icicles around saline springs at Shiowakka, Hokkaido Island, Japan. Here, ikaite forms as a 'rimstone' and as calcareous encrustation around the springs that are draining an area of ground containing volcanic rocks. During the winter the average air temperatures drop to -4.3°C chilling the spring water as it is discharged from the ground. The chemistry of the spring water is favourable to ikaite precipitation in that it contains calcium and known inhibitors of calcite formation.
Ikaite formation at Shiowakka is seasonal and ceases when air temperatures rise. The ikaite which has formed then reverts to calcite and water and is lost. In this way the ikaite formation at Shiowakka is similar to that around springs on the shores of Mono Lake. It might be that ikaite forms around springs in many other locations around the World but most workers simply miss it due to its ephemeral nature.
There have been a number of reported findings of ikaite growing displasively within sediments from a variety of different geological settings across the World. The first of these was made twenty years after Pauly's initial discovery by Suess et al. (1982) on the research ship Polar Star. Suess and his colleagues discovered large, amber coloured crystals embedded in sediment cores recovered from the deep waters (1950 metres) of the Bransfield Strait over the Antarctic shelf (left). Subsequent analysis identified the mineral as ikaite which Suess and his co-workers believed to be forming in the sub-zero bottom conditions from the interstitial solutions of organic-rich sediments undergoing microbial decomposition.
Following Suess et al. initial discovery a number of similar ikaite discoveries have followed. Published accounts of such discoveries include ikaite from: mud cores recovered by the research ship Glomar Challenger from the Nankai trough off Japan (Stein & Smith, 1985), crystals observed in cores from sediments of the Zaire deep-sea fan by Jansen et al. (1987) and from esturine mud on the Alaskan coast (Kennedy et al. 1987). It was the form of these large displacively grown crystals and their mode of occurrence that promises to solve a geological mystery that had persisted for over 150 years. It seems quite probable now that ikaite was the precursor mineral of crystal pseudomorphs, often called 'glendonites', known from a number of formations of different ages around the world (Suess et al., 1982; Shearman & Smith, 1985). The thumbnail picture here is of glendonites which superficially have the appearance of fresh ikaite crystals recovered from muddy sediments.
A number of similar but as yet unpublished discoveries of ikaite crystals found in sediment cores have been related to the authors. It is also noted that one such discovery has been reported by scientists on the Internet Ikaite found in the Laptev Sea
Many authors reporting discoveries of natural ikaite include some discussion of ikaite as the precursor mineral to a suite of crystal pseudomorphs known as 'glendonites' (Kaplan, 1979; Suess, 1982; Shearman & Smith, 1985). Whilst the evidence is mounting that many of these pseudomorphs are indeed after ikaite the precursor mineral has not been unequivocally identified. Readers are directed to some of the publications below for further information on glendonites particularly the papers by: Kaplan, 1979, Shearman and Smith (1985) and Shearman et al., 1989).
Bo Shultz, a Masters student at Aahus University, Denmark, is currently conducting an intensive study of glendonite pseudomorphs, especially the large specimens found in the Moler Clay, North West Jutland, Denmark. He can be contacted at: geolbps@aau.dk
Buchardt, B, Seaman, P. G., Düwel, L., Kristiansen, R. M., Kristiansen, A., Pedersen, G. H., Stockmann, G., Thorbjørn, L., Vous, M., Whiticar, M. J., & Wilken, U., 1997. Submarine columns of ikaite tufa. Nature. November 13. 390 issue number 6656.
Council, T. C. & Bennett, P. C. 1993. Geochemistry of ikaite formation at Mono Lake, California: Implications for the origin of tufa mounds. Geology, 21, 971-974.
Dana, E. S., 1884. A crystallographic study of the thinolites of Lake Lahonton: U. S. Geological Survey Bulletin, 12. 429-486.
Ito, T., 1996. Ikaite from cold spring water at Shiowakka , Hokkaido. Genko. 91(6). 209-219
Jansen, J. H. F., Woensdregt, C. F., Kooistra, M. J. and van de Gaast, S. J., 1987. Ikaite pseudomorphs in the Zaire deep-sea fan: An intermediate between calcite and porous calcite. Geology, 15, 245-248
Kaplan, M. E., 1979. Calcite pseudomorphs (pseudogalussite, jarrowite, thinolite, glendonite, gennoishi, White sea hornlets) in sedimentary rocks. Plenum Publishing Corporation 1980. Translated from Lithologiya I Poleznye, 5, 125-141.
Kennedy, G. L., Hopkins D.M., & Pickthorn W.J., 1987. Ikaite, the glendonite precursor, in estuarine sediments at Barrow, Arctic Alaska. Geological Survey of Alaska Annual Meeting, Abstract, Programme 9, 725.
King, C., 1878. U. S. Geological exploration of the fortieth parallel, Vol. 1. Washington: D.C., U. S. Government Printing Office.
Russell, I. C., 1883. Sketch of the Geological History of Lake Lahonton, a Quaternary Lake of northwestern Nevada. U.S. Geological Survey, 3rd Annual Report for 1881-1882, 189-235.
Russell, I. C., 1889. Quaternary History of Mono Valley, California. Reprint from the Eighth Annual Report of the United States Geological Survey, Artemisia Press, Lee Vining, California 1984. 267-394
Shearman, D. J. & Smith, A. J., 1985. Ikaite, the parent mineral of jarrowite-type pseudomorphs. Proceedings of the Geologists' Association of London, 96, 305-314.
Shearman, D. J., McGugan, A., Stein, C., & Smith, A. J., 1989. Ikaite, CaCO3·6H2O, the precursor of the thinolites in the Quaternary tufas and tufa mounds of the Lahontan and Mono Lake Basins, western United States. Bulletin of the Geological Society of America, 101. 913 - 917.
Stein & Smith., 1985. Authigenic carbonate nodules in the Nankai Trough, Site 583. Initial reports of the Deep Sea Drilling Project, 87, 659-668.
Suess, E., Balzer, W., Hesse, K-F., Muller,P.J., Ungerer, C.A., & Wefer,G., 1982. Calcium Carbonate Hexahydrate from Organic-Rich Sediments of the Arctic Shelf: Precursors of Glendonites. Science, 1216, 1128-1130.
