Dating pseudotachylyte of the Asuke Shear Zone using zircon fission-track and U–Pb methods

2006 ◽  
Vol 424 (1-2) ◽  
pp. 99-107 ◽  
Author(s):  
Masaki Murakami ◽  
Jan Košler ◽  
Hideo Takagi ◽  
Takahiro Tagami
Keyword(s):  
Shear Zone ◽  
Fission Track ◽  
Zircon Fission Track

Fission-track evidence for Cenozoic uplift of the Nelson batholith, southeastern British Columbia

1989 ◽  
Vol 26 (10) ◽  
pp. 1944-1952 ◽  
Author(s):  
Donald S. Sweetkind ◽  
Ian J. Duncan
Keyword(s):  
British Columbia ◽  
Shear Zone ◽  
Fault Zone ◽  
Fission Track ◽  
Gneiss Dome ◽  
Rapid Cooling ◽  
Zircon Fission Track ◽  
Rapid Uplift

Apatite and zircon fission-track data from the Nelson batholith in southeastern British Columbia reveal that a significant amount of uplift has occurred since Paleocene time, including an episode of rapid uplift during Eocene time. Age versus elevation curves for apatite and zircon, combined with a calculated present depth to the 105 °C apatite-annealing isotherm, suggest that some 6 km of apparent uplift has occurred in the vicinity of the Nelson batholith since Paleocene time. A period of rapid cooling and uplift occurred from 59 to 45 Ma, when the bounding faults of the adjacent Valhalla gneiss dome, the Valkyr shear zone, and the Slocan Lake fault zone were active. The rapid uplift is interpreted as being related to Eocene extension and the rise of the adjacent Valhalla gneiss dome during Eocene time.

Downstream Changes of Alpine Zircon Fission-Track Ages in the Rhone and Rhine Rivers

2004 ◽  
Vol 74 (1) ◽  
pp. 82-94 ◽  
Author(s):  
M. Bernet ◽  
M. T. Brandon ◽  
J. I. Garver ◽  
B. Molitor
Keyword(s):  
Fission Track ◽  
Zircon Fission Track ◽  
Fission Track Ages

Low-temperature thermal history of the Gilmore Dome area, Fairbanks Mining District, Alaska

1993 ◽  
Vol 30 (4) ◽  
pp. 764-768 ◽  
Author(s):  
John M. Murphy ◽  
Arne Bakke
Keyword(s):  
Gold Deposit ◽  
Fission Track ◽  
Hydrothermal Fluids ◽  
Mining District ◽  
Cooling Path ◽  
Alteration Assemblage ◽  
Zircon Fission Track ◽  
History Of ◽  
Maximum Temperatures ◽  
Fission Track Ages

Eight apatite and two zircon fission-track ages provide evidence of complex Tertiary thermal overprinting by hydrothermal fluids in the Gilmore Dome area. Five ages on apatite from the Fort Knox gold deposit average 41 Ma, one from the Stepovich prospect is 80 Ma, and two from Pedro Dome average 67 Ma. Elevations of these samples overlap but their ages do not, indicating that each area experienced a different thermal history.Ages of apatite from the Fort Knox gold deposit decrease with elevation from 42 to 36 Ma but have data trends indicative of complex cooling. Two ~51 Ma ages on zircon indicate that maximum temperatures approached or exceeded ~180 °C. An alteration assemblage of chalcedony + zeolite + calcite + clay in the deposit resulted from deposition by a paleo-hydrothermal system. The data suggest that the system followed a complex cooling path from > 180 to < 110 °C between 51 and 36 Ma, and that final cooling to below 60 °C occurred after ~25 Ma.The 80 Ma age from Stepovich prospect either resulted from cooling after intrusion of the underlying pluton (~90 Ma) or records postintrusion thermal overprinting sometime after ~50 Ma. The 67 Ma samples from Pedro Dome may also have experienced partial age reduction during later heating. The differences in the data from the different areas and the presence of a late alteration assemblage at Fort Knox suggest that the fluids responsible for heating were largely confined to the highly fractured and porous Fort Knox pluton.

Effects of Etching on Zircon Grains and its Implications for the Fission Track Method

2012 ◽  
Vol 66 (5) ◽  
pp. 545-551 ◽  
Author(s):  
Carlos Alberto Tello Sáenz ◽  
Eduardo Augusto Campos Curvo ◽  
Airton Natanael Coelho Dias ◽  
Cleber José Soares ◽  
Carlos José Leopoldo Constantino ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Crystal Lattice ◽  
Fission Track ◽  
Surface Characteristics ◽  
Optical Microscope ◽  
Etching Time ◽  
X Ray ◽  
Track Method ◽  
Zircon Fission Track ◽  
Natural Zircon

Studies of zircon grains using optical microscopy, micro-Raman spectroscopy, and scanning electron microscopy (SEM) have been carried out to characterize the surface of natural zircon as a function of etching time. According to the surface characteristics observed using an optical microscope after etching, the zircon grains were classified as: (i) homogeneous; (ii) anomalous, and (iii) hybrid. Micro-Raman results showed that, as etching time increases, the crystal lattice is slightly altered for homogeneous grains, it is completely damaged for anomalous grains, and it is altered in some areas for hybrid grains. The SEM (energy dispersive X-ray spectroscopy, EDS) results indicated that, independent of the grain types, where the crystallinity remains after etching, the chemical composition of zircon is approximately 33% SiO2:65% ZrO2 (standard natural zircon), and for areas where the grain does not have a crystalline structure, there are variations of ZrO2 and, mainly, SiO2. In addition, it is possible to observe a uniform surface density of fission tracks in grain areas where the determined crystal lattice and chemical composition are those of zircon. Regarding hybrid grains, we discuss whether the areas slightly altered by the chemical etching can be analyzed by the fission track method (FTM) or not. Results of zircon fission track and U-Pb dating show that hybrid and homogeneous grains can be used for dating, and not only homogeneous grains. More than 50 sedimentary samples from the Bauru Basin (southeast Brazil) were analyzed and show that only a small amount of grains are homogeneous (10%), questioning the validity of the rest of the grains for thermo-chronological evolution studies using zircon FTM dating.

Sign in / Sign up

Export Citation Format

Share Document