Quick
Search: 		  
advanced search
 GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help 
Clays and Clay Minerals Email Content Delivery
JOURNAL HOME HELP CONTACT PUBLISHER SUBSCRIBE ARCHIVE SEARCH TABLE OF CONTENTS
Clays and Clay Minerals; April 2001; v. 49; no. 2; p. 141-155
© 2001 Clay Minerals Society
This Article
Right arrow Figures Only
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in Web of Science
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Web of Science (12)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Yan, Y.
Right arrow Articles by Simmons, S. F.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation

GENESIS OF DIOCTAHEDRAL PHYLLOSILICATES DURING HYDROTHERMAL ALTERATION OF VOLCANIC ROCKS: II. THE BROADLANDS-OHAAKI HYDROTHERMAL SYSTEM, NEW ZEALAND

Yonghong Yan1, David A. Tillick2, Donald R. Peacor1 and Stuart F. Simmons3

1 Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan 48109, USA
2 Geology Department, University of Auckland, Private Bag, 92019, Auckland, New Zealand
3 Geothermal Institute, University of Auckland, Private Bag, 92019, Auckland, New Zealand

E-mail of corresponding author: drpeacor{at}umich.edu

The clay mineral textures, assemblages, formation mechanisms, and controlling geological parameters relating to alteration of silicic volcanic rocks by hydrothermal solutions, in core samples from the Broadlands-Ohaaki hydrothermal system, New Zealand, were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission and analytical electron microscopy (TEM/ AEM). Mineralogical and textural relations of this active hydrothermal system, for which temperatures and fluid relations are well known, are equivalent to those in the Golden Cross hydrothermal gold deposit as described in Part 1.

XRD data show a sequence of clay minerals from smectite to a range of interstratified I–S to mica with increasing depth and temperature, on average. TEM observations are in general agreement with XRD data, especially with respect to relative proportions of illite (I)- and smectite (S)- like layers. TEM data also show that: (1) Smectite packets contain no discrete illite-like layers in samples identified as (Reichweite, R = 0) I–S by XRD. They coexist with separate packets of (R = 1) I–S. (2) A continuous range in I–S occurs from (R = 1) I–S with increasing proportion of illite-like layers, but at high illite-like layer contents there is a gap between I–S and illite. (3) 1M and 2M1 polytypes of mica coexist in separate packets, but the rare 1M polytype has a larger VIMg content.

The data imply that clay minerals formed by dissolution and neocrystallization directly from volcanic phases, although multiple reaction events can not be ruled out. Such "episodic" alteration produces a sequence of clay minerals identical to those of prograde diagenesis of pelitic sediments. This result implies that the presence of a continuous sequence is not definitive proof of continuous sequences of transformation as a function of time and continuous burial. Reaction progress of the clay-mineral sequence is in general accord with the known temperature gradient, but with significant and common exceptions. High porosity and permeability, both inherent in rock texture and local structure, are inferred to foster local reaction progress, as consistent with metastability of phases and the Ostwald step rule.

Key Words: Crystallization • Dioctahedral Phyllosilicates • Hydrothermal System • Illite-Smectite (I–S) • Polytypism • Transmission Electron Microscopy




This article has been cited by other articles:


Home page
 Clay MineralsHome page
G. GIORGETTI, F. S. AGHIB, K. J. T. LIVI, A.-C. GAILLOT, and T. J. WILSON
Newly formed phyllosilicates in rock matrices and fractures from CRP-3 core (Antarctica): an electron microscopy study
Clay Minerals, March 1, 2007; 42(1): 21 - 43.
[Abstract] [Full Text] [PDF]

Home page
 Clays and Clay MineralsHome page
A. Inoue, B. Lanson, M. Marques-Fernandes, B. A. Sakharov, T. Murakami, A. Meunier, and D. Beaufort
ILLITE-SMECTITE MIXED-LAYER MINERALS IN THE HYDROTHERMAL ALTERATION OF VOLCANIC ROCKS: I. ONE-DIMENSIONAL XRD STRUCTURE ANALYSIS AND CHARACTERIZATION OF COMPONENT LAYERS
Clays and Clay Minerals, October 1, 2005; 53(5): 423 - 439.
[Abstract] [Full Text] [PDF]

Home page
 Clays and Clay MineralsHome page
T. Murakami, A. Inoue, B. Lanson, A. Meunier, and D. Beaufort
ILLITE-SMECTITE MIXED-LAYER MINERALS IN THE HYDROTHERMAL ALTERATION OF VOLCANIC ROCKS: II. ONE-DIMENSIONAL HRTEM STRUCTURE IMAGES AND FORMATION MECHANISMS
Clays and Clay Minerals, October 1, 2005; 53(5): 440 - 451.
[Abstract] [Full Text] [PDF]

Home page
 Clays and Clay MineralsHome page
A. Inoue, A. Inoue, A. Meunier, and D. Beaufort
ILLITE-SMECTITE MIXED-LAYER MINERALS IN FELSIC VOLCANICLASTIC ROCKS FROM DRILL CORES, KAKKONDA, JAPAN
Clays and Clay Minerals, February 1, 2004; 52(1): 66 - 84.
[Full Text] [PDF]

Home page
 Clay MineralsHome page
G. Giorgetti, G. GIORGETTI, M. P. MATA, and D. R. PEACOR
Evolution of mineral assemblages and textures from sediment through hornfels in the Salton Sea Geothermal Field: Direct crystallization of phyllosilicates in a hydrothermal-metamorphic system
Clay Minerals, March 1, 2003; 38(1): 113 - 126.
[Abstract] [Full Text] [PDF]

Home page
 Clays and Clay MineralsHome page
D. R. Peacor, D. R. Peacor, B. Bauluz, H. Dong, D. Tillick, and Y. Yan
TRANSMISSION AND ANALYTICAL ELECTRON MICROSCOPY EVIDENCE FOR HIGH Mg CONTENTS OF 1M ILLITE: ABSENCE OF 1M POLYTYPISM IN NORMAL PROGRADE DIAGENETIC SEQUENCES OF PELITIC ROCKS
Clays and Clay Minerals, December 1, 2002; 50(6): 757 - 765.
[Abstract] [Full Text] [PDF]

Home page
 American MineralogistHome page
P. H. Nadeau, D. R. Peacor, J. Yan, and S. Hillier
I-S precipitation in pore space as the cause of geopressuring in Mesozoic mudstones, Egersund Basin, Norwegian continental shelf
American Mineralogist, November 1, 2002; 87(11-12): 1580 - 1589.
[Abstract] [Full Text] [PDF]

Home page
 Clays and Clay MineralsHome page
J.-w. Kim, J.-w. Kim, and D. R. Peacor
CRYSTAL-SIZE DISTRIBUTIONS OF CLAYS DURING EPISODIC DIAGENESIS: THE SALTON SEA GEOTHERMAL SYSTEM
Clays and Clay Minerals, June 1, 2002; 50(3): 371 - 380.
[Abstract] [Full Text] [PDF]

Home page
 Clays and Clay MineralsHome page
B. Bauluz, B. Bauluz, D. R. Peacor, and R. F. Ylagan
TRANSMISSION ELECTRON MICROSCOPY STUDY OF SMECTITE ILLITIZATION DURING HYDROTHERMAL ALTERATION OF A RHYOLITIC HYALOCLASTITE FROM PONZA, ITALY
Clays and Clay Minerals, April 1, 2002; 50(2): 157 - 173.
[Abstract] [Full Text] [PDF]

Home page
 Clays and Clay MineralsHome page
D. A. Tillick, D. A. Tillick, D. R. Peacor, and J. L. Mauk
GENESIS OF DIOCTAHEDRAL PHYLLOSILICATES DURING HYDROTHERMAL ALTERATION OF VOLCANIC ROCKS: I. THE GOLDEN CROSS EPITHERMAL ORE DEPOSIT, NEW ZEALAND
Clays and Clay Minerals, April 1, 2001; 49(2): 126 - 140.
[Abstract] [Full Text] [PDF]

Home page
 Geological Society, London, Special PublicationsHome page
Y. Yan, B. A. van der Pluijm, and D. R. Peacor
Deformation microfabrics of clay gouge, Lewis Thrust, Canada: a case for fault weakening from clay transformation
Geological Society, London, Special Publications, January 1, 2001; 186(1): 103 - 112.
[Abstract] [PDF]


JOURNAL HOME HELP CONTACT PUBLISHER SUBSCRIBE ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 2009 by Clay Minerals Society