Synthetic fluid inclusions. XV. TEM investigation of plastic flow associated with reequilibration of fluid inclusions in natural quartz

被引:74
作者
Vityk, MO
Bodnar, RJ [1 ]
Doukhan, JC
机构
[1] Virginia Polytech Inst & State Univ, Dept Geol Sci, Fluids Res Lab, Blacksburg, VA 24061 USA
[2] Univ Sci & Tech Lille Flandres Artois, Lab Struct & Proprietes Etat Solide, F-59655 Villeneuve Dascq, France
基金
美国国家科学基金会;
关键词
D O I
10.1007/s004100000142
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
The nature and abundance of dislocations in quartz surrounding fluid inclusions were studied to obtain a better understanding of processes associated with fluid inclusion reequilibration. Synthetic fluid inclusions containing 10 wt% NaCl aqueous solution were formed in three samples at 700 degrees C and 5 kbar. One of the samples was quenched along an isochore to serve as a reference sample. The other two samples were quenched along a P-T path that generated internal pressures in excess of the confining pressure. The two samples were held at the final reequilibration P-T conditions of 625 degrees C and 2 kbar for 30 and 180 days, respectively. Following the experiments, microstructures associated with fluid inclusions were examined with the TEM. Quartz in healed fractures in the reference sample that was quenched isochorically shows a moderate dislocation activity. Quartz adjacent to reequilibrated fluid inclusions in the other two samples, however, showed a marked increase in dislocation activity compared to the un-reequilibrated sample. Deformation of the inclusion walls occurred anisotropically by expansion of mobile dislocations in their slip systems. Dislocation expansion was controlled by glide in the rhombohedral planes {1 0 1 1} that was restricted to narrow zones (less than or equal to 3 mu m) in the immediate vicinity of the fluid inclusion walls outside of the healed fracture plane. These plastic zones were observed after both short term (30 days) and long term (180 days) experiments and are attributed to hydrolytic weakening of quartz around fluid inclusions owing to diffusion of water into the quartz matrix during the experiment. The close spatial association of submicroscopic water bubbles with dislocations, and the rarity of water bubbles in the reference sample, show clearly that in both the 30 and 180 day experiments reequilibration involves water loss from the fluid inclusions. Our results indicate that synthetic fluid inclusions in this study recover (chemically and volumetrically), even at relatively fast experimental loading rates, such that internal stresses never reach the point of brittle failure. The driving force for fluid inclusion deformation involves two related mechanisms: plastic deformation of hydrolytically weakened wet quartz in the healed fracture, and water leakage associated with preexisting and strain-induced dislocations.
引用
收藏
页码:285 / 297
页数:13
相关论文
共 55 条
[1]  
[Anonymous], 1964, Trans. Am. Geophys. Union
[2]   Mobility and H2O loss from fluid inclusions in natural quartz crystals [J].
Audétat, A ;
Günther, D .
CONTRIBUTIONS TO MINERALOGY AND PETROLOGY, 1999, 137 (1-2) :1-14
[3]   A MECHANISM FOR PREFERENTIAL H2O LEAKAGE FROM FLUID INCLUSIONS IN QUARTZ, BASED ON TEM OBSERVATIONS [J].
BAKKER, RJ ;
JANSEN, JB .
CONTRIBUTIONS TO MINERALOGY AND PETROLOGY, 1994, 116 (1-2) :7-20
[4]   PREFERENTIAL WATER LEAKAGE FROM FLUID INCLUSIONS BY MEANS OF MOBILE DISLOCATIONS [J].
BAKKER, RJ ;
JANSEN, JB .
NATURE, 1990, 345 (6270) :58-60
[5]   CALCULATED FLUID EVOLUTION PATH VERSUS FLUID INCLUSION DATA IN THE COHN SYSTEM AS EXEMPLIFIED BY METAMORPHIC ROCKS FROM ROGALAND, SOUTH-WEST NORWAY [J].
BAKKER, RJ ;
JANSEN, JBH .
JOURNAL OF METAMORPHIC GEOLOGY, 1993, 11 (03) :357-370
[6]   EXPERIMENTAL POST-ENTRAPMENT WATER-LOSS FROM SYNTHETIC CO2-H2O INCLUSIONS IN NATURAL QUARTZ [J].
BAKKER, RJ ;
JANSEN, JBH .
GEOCHIMICA ET COSMOCHIMICA ACTA, 1991, 55 (08) :2215-2230
[7]   POST-ENTRAPMENT MODIFICATION OF FLUID INCLUSIONS DUE TO OVERPRESSURE - EVIDENCE FROM NATURAL SAMPLES [J].
BARKER, AJ .
JOURNAL OF METAMORPHIC GEOLOGY, 1995, 13 (06) :737-750
[8]  
Bodnar R.J., 1994, Fluid inclusions in minerals: Methods and applications: International Mineralogical Association Short Course Manual, P117
[9]   SYNTHETIC FLUID INCLUSIONS .6. QUANTITATIVE-EVALUATION OF THE DECREPITATION BEHAVIOR OF FLUID INCLUSIONS IN QUARTZ AT ONE ATMOSPHERE CONFINING PRESSURE [J].
BODNAR, RJ ;
BINNS, PR ;
HALL, DL .
JOURNAL OF METAMORPHIC GEOLOGY, 1989, 7 (02) :229-242