TY - JOUR
T1 - Granite generation and rapid unroofing related to strike-slip faulting, Aysén, Chile
AU - Hervé, Francisco
AU - Pankhurst, Robert J.
AU - Drake, Robert
AU - Beck, Myrl E.
AU - Mpodozis, Constantino
N1 - Funding Information:
This work was supportedb y FONDECYT grant 1181/90,b y NSF grant EAR 8718896a nd by National GeographicS ocietygrant 3738-88. Chemicala nd EPMA analysesw ere carrieodu t, during a CE scholarshipto F.H., at Laboratoire de PetrologieM agmatiqueU, niversit6d e Marseille. Rb-Sr data weroeb tainedd uringa visit by F.H. to the NERC IsotopeG eoscienceLsa bora-tory, Keyworth,U .K., with the approvalo f Dr.
PY - 1993/12
Y1 - 1993/12
N2 - A stock of biotite-muscovite-garnet leucogranite crops out in the lower course of Río Cisnes as an unusual minor lithology within the predominantly dioritic to tonalitic North Patagonian Batholith. Foliated and unfoliated varieties are present-the former are nearer to the main lineament of the Liquiñe-Ofqui Fault Zone (LOFZ). Two-feldspar thermometry indicates equilibration temperatures above 600°C, for pressures probably not over 3 kbar, as suggested by the Mn-rich garnet composition. A Rb-Sr whole-rock isochron age of 9.6 ± 0.4 Ma (1σ error) probably indicates the time of magma crystallization. 40Ar-39Ar ages of 6.6 ± 0.3 Ma on muscovite and 5.5 ± 0.4 Ma on biotite are cooling ages from which a moderate average uplift/denudation rate (∼ 1 mm/yr) may be calculated. Paucity of occurrence, distribution close to the LOFZ and a near minimum-melt composition all suggest that the leucogranite magma was derived by partial melting of the lower crust, perhaps by decompression melting at a time when uplift/denudation rates were high (4 mm/yr or more are required). Regional evidence for rapid Holocene uplift in the immediate vicinity of the LOFZ substantiates the feasibility of the proposed petrogenetic model, which may be valid in other strike-slip orogenic environments.
AB - A stock of biotite-muscovite-garnet leucogranite crops out in the lower course of Río Cisnes as an unusual minor lithology within the predominantly dioritic to tonalitic North Patagonian Batholith. Foliated and unfoliated varieties are present-the former are nearer to the main lineament of the Liquiñe-Ofqui Fault Zone (LOFZ). Two-feldspar thermometry indicates equilibration temperatures above 600°C, for pressures probably not over 3 kbar, as suggested by the Mn-rich garnet composition. A Rb-Sr whole-rock isochron age of 9.6 ± 0.4 Ma (1σ error) probably indicates the time of magma crystallization. 40Ar-39Ar ages of 6.6 ± 0.3 Ma on muscovite and 5.5 ± 0.4 Ma on biotite are cooling ages from which a moderate average uplift/denudation rate (∼ 1 mm/yr) may be calculated. Paucity of occurrence, distribution close to the LOFZ and a near minimum-melt composition all suggest that the leucogranite magma was derived by partial melting of the lower crust, perhaps by decompression melting at a time when uplift/denudation rates were high (4 mm/yr or more are required). Regional evidence for rapid Holocene uplift in the immediate vicinity of the LOFZ substantiates the feasibility of the proposed petrogenetic model, which may be valid in other strike-slip orogenic environments.
UR - http://www.scopus.com/inward/record.url?scp=0027865121&partnerID=8YFLogxK
U2 - 10.1016/0012-821X(93)90251-4
DO - 10.1016/0012-821X(93)90251-4
M3 - Article
AN - SCOPUS:0027865121
SN - 0012-821X
VL - 120
SP - 375
EP - 386
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
IS - 3-4
ER -