In:
Economic Geology, Society of Economic Geologists, Inc., Vol. 115, No. 2 ( 2020-03-01), p. 415-441
Abstract:
Jiaodong gold deposits are mainly sited along faulted contacts between Upper Jurassic Linglong granite and Precambrian basement metamorphic rocks or Lower Cretaceous Guojialing granite. Long-standing controversies relate to timing of gold mineralization and granite-gold relationships. In this study, gold-related muscovite consistently provides concordant 40Ar/39Ar plateau ages of 120 ± 2 Ma (2σ) for the Jiaojia, Sizhuang, and Luoshan deposits. Analogous 40Ar/39Ar timing constraints from gold-related muscovite are provided by total gas and high-temperature ages from Fushan, concordant high-temperature ages from Rushan, and fusion-step ages from Xiadian deposits. These new 40Ar/39Ar ages, when combined with previous reliable 40Ar/39Ar and U-Pb age constraints for mineralization, including ages of pre- and postgold dikes, define a widespread gold mineralization event at 120 ± 2 Ma (2σ). Published zircon U-Pb ages for Guojialing and Aishan granite magmatism suggest an ~8-m.y. lag between peak intrusive activity and gold mineralization. This, together with lack of both high-temperature alteration assemblages and alteration and/or metal zonation, indicates that the structurally controlled Jiaodong deposits are orogenic rather than intrusion-related deposits. Despite this, granite intrusions are considered to have provided suitable fluid trap sites. New 40Ar/39Ar analyses of biotite from the Linglong and Guojialing granites show they had cooled to about ~300° ± 50°C by ca. 123 to 124 Ma, providing pressure-temperature conditions similar to those under which most orogenic gold deposits formed close to the ductile-brittle transition. This enabled the effective ingress of fluids at supralithostatic pressures at 120 ± 2 Ma, leading to intensive brecciation, alteration, and deposition of both vein-type and disseminated gold ores. New zircon (U-Th)/He dates together with apatite fission-track data indicate that preservation of the gold province is due to slow postmineralization uplift and exhumation.
Type of Medium:
Online Resource
ISSN:
1554-0774
,
0361-0128
DOI:
10.5382/econgeo.4716
Language:
English
Publisher:
Society of Economic Geologists, Inc.
Publication Date:
2020
detail.hit.zdb_id:
217703-1
detail.hit.zdb_id:
2091221-3
SSG:
13
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