 |
| Detailed Reference Information |
|---|
|
Stroncik, N.A. and Schmincke, H.U. (2001). Evolution of palagonite: Crystallization, chemical changes, and element budget. Geochemistry, Geophysics, Geosystems 2. |
|
|
The structural and chemical evolution of palagonite was studied as a function of glass composition, alteration environment, and time by applying a range of analytical methods (electron microprobe, infrared photometry, atomic force microscopy, X-ray fluorescence, and X-ray diffraction). Palagonitization of volcanic glass is a continuous process of glass dissolution palagonite formation, and palagonite evolution, which can be subdivided into two different reaction stages with changing element mobilities. The first stage is characterized by congruent dissolution of glass and contemporaneous precipitation of 'fresh,' gel-like, amorphous, optically isotropic, mainly yellowish palagonite. This stage is accompanied by loss of Si, Al, Mg, Ca, Na, and K, active enrichment of H2O and the passive enrichment of Ti and Fe. The second stage is an aging process during which the thermodynamically unstable palagonite reacts with the surrounding fluid and crystallizes to smectite. This stage is accompanied by uptake of Si, Al, Mg, and K from solution and the loss of Ti and H2O. Ca and Na are still showing losses, whereas Fe reacts less consistently, remaining either unchanged or showing losses. The degree and direction of element mobility during palagonitization was found to vary mainly with palagonite aging, as soon as the first precipitation of palagonite occurs. This is indicated by the contrasting major element signatures of palagonites of different aging steps, by the changes in the direction of element mobility with palagonite aging, and by the general decrease of element loss with increasing formation of crystalline substances in the palagonite. Considering the overall element budget of a water-rock system, the conversion of glass to palagonite is accompanied by much larger element losses than the overall alteration process, which includes the formation of secondary phases and palagonite aging. The least evolved palagonitized mafic glass studied has undergone as much as 65 wt% loss of elements during palagonite formation compared to similar to 28 wt% element loss during bulk alteration. About 33 wt% element loss was calculated for one of the more evolved, in terms of the aging degree, rocks studied, compared to almost no loss for bulk alteration. |
|
|
|
| BACKGROUND DATA FILES |
|
 |
Abstract |
 |
 |
|
|
Entire Document PDF |
|
|
|
|
Table 1A |
|
|
|
Table 1B |
|
|
|
Table 1C |
|
|
|
Table 1D |
|
|
|
Table 1E |
|
|
|
Table 2A |
|
|
|
Table 2B |
|
|
|
Table 2C |
|
|
|
Table 2D |
|
|
|
Table 2E |
|
|
|
Table 2F |
|
|
|
Table 2G |
|
|
|
Table 3 |
|
|
|
Table 4 |
|
|
|
Table 5 |
|
|
|
Table 6A |
|
|
|
Table 6B |
|
|
|
|
Electron Microprobe |
|
|
|
Infrared Photometry |
|
|
|
X-Ray Fluorescence Analysis |
|
|
|
X-Ray Diffraction |
|
|
|
|
|
Keywords
glass alteration, palagonite aging, mass balancing, ostwald step rule, biologically mediated dissolution, water-rock interactions, basaltic glass, microbial activity, volcanic glass, oceanic-crust, seawater, mechanism, interface, mountains |
|
Publisher
American Geophysical Union
2000 Florida Avenue N.W.
Washington, D.C. 200009-1277
USA
1-202-462-6900
1-202-328-0566
service@agu.org |
|
|
|