In:
Geological Journal, Wiley, Vol. 55, No. 4 ( 2020-04), p. 2447-2472
Abstract:
The Hetai goldfield is one of the largest gold mining districts in the South China Block. A complex paragenesis consists of three mineralization stages: syntectonic metamorphic stage, hydrothermal stage, and supergene stage. The syntectonic metamorphic stage is characterized by banded quartz (Q1) and invisible Au in mylonites. The hydrothermal stage, which is the main gold mineralization stage, can be divided into three substages: an early substage characterized by coarse‐grained quartz (Q2) + pyrite + arsenopyrite + pyrrhotite, an intermediate substage characterized by gray fine‐grained quartz (Q3) + electrum + poly‐sulphides + sericite + chlorite and a late substage with predominate white quartz (Q4) + calcite as well as lesser sulphides. During the supergene stage, malachite, covellite, and limonite were formed. Four types of fluid inclusions (FIs) in these types of quartz were identified: aqueous FIs (type 1), CO 2 ‐bearing aqueous FIs (type 2), CO 2 ‐rich FIs (type 3), and solid‐bearing FIs (type 4). Q1 only contains type 1 FIs; Q2 contains types 2 and 4 FIs; Q3 contains types 2 and 3 FIs; and Q4 only contains type 1 FIs. Microthermometric results show that the homogenization temperatures of fluid inclusions range from 350°C to 400°C for Q1, 250°C to 320°C for Q2, 138°C to 245°C for Q3, and 110°C to 207°C for Q4. Salinities of fluid inclusions range from 3.4 to 5.7 wt.%, 2.6 to 12.9 wt.%, 0.5 to 11.5 wt.%, and 0.2 to 7.3 wt.% for Q1, Q2, Q3, and Q4, respectively. Alteration minerals (sericite and chlorite) from the main mineralization stage have δDH 2 O‐VSMOW values of −62‰ to −98‰ and calculated δ 18 OH 2 O‐VSMOW values of 6.3‰ to 4.4‰. The in situ sulphur isotope analysis of pyrite yields a narrow δ 34 S CDT range of −1.5‰ to −5.2‰ (average −3.4‰), combined with the Pb isotopic compositions of the sulphides, wall rocks, and Wucun pluton, revealing that the ore‐forming material was mainly derived from magmatic source. The mineralization age (sericite 40 Ar/ 39 Ar: 159.3 ± 0.8 Ma) is close to the emplacement age of Wucun biotite monzonitic granite pluton (LA‐ICP‐MS zircon U–Pb age: 158.1 ± 1.9 Ma). These geochemical and geochronological data suggest that the main phase of gold mineralization in the Hetai goldfield is genetically related to the granitic activities in the Late Jurassic rather than the mylonitization event in the Late Triassic to Early Jurassic.
Type of Medium:
Online Resource
ISSN:
0072-1050
,
1099-1034
Language:
English
Publisher:
Wiley
Publication Date:
2020
detail.hit.zdb_id:
1479201-1
SSG:
13
