In:
Geological Journal, Wiley, Vol. 55, No. 6 ( 2020-06), p. 4525-4542
Abstract:
Demingding is a poorly studied post‐collisional porphyry Cu‐Mo deposit, located in the eastern part of the Gangdese porphyry copper belt. In this study, we present LA‐ICP‐MS zircon U‐Pb dating, whole‐rock geochemistry, and zircon trace elemental data for the mineralization related biotite monzogranite porphyry in Demingding. Zircon U‐Pb dating shows that the weighted mean 206 Pb/ 238 U ages of the Miocene biotite monzogranite porphyry is 20.36 ± 0.46 Ma (MSWD = 2.6, n = 21). The Miocene biotite monzogranite porphyry is characterized by high SiO 2 , K 2 O, and Al 2 O 3 contents and shows adakite‐like signatures. These rocks have high Sr/Y ratios, fractionated REE patterns with low HREE abundances, enrichment in LILE compared with HFSE, and have ( 87 Sr/ 86 Sr) i values of 0.7059 to 0.7062, ε Nd ( t ) values of −2.35 to −1.67 and ( 206 Pb/ 204 Pb) i ratios of 18.50–18.55. These features are similar to other Miocene adakite‐like intrusions in the Gangdese belt. We propose that the biotite monzogranite porphyry shares the same petrogenesis with other Miocene ore‐bearing adakite‐like intrusions in the Eastern Gangdese belt and was derived from remelting of the subduction‐modified, eclogitized Tibetan lower crust and mixing with hydrous mafic magmas from metasomatized Tibetan mantle. The zircons from biotite monzogranite porphyry have only minimal negative Eu anomalies (Eu N /Eu N * 〉 0.3), and exhibit large ratios of Ce 4+ /Ce 3+ (average value of 113), 10,000*(Eu N /Eu N *)/Y (3.94–8.14, 〉 1), Ce/Nd (9–58, Average value of 30), (Ce/Nd)/Y (0.008–0.127, 〉 0.003), and low value of Dy/Yb (0.15–0.24, 〈 0.3), indicating that the biotite monzogranite porphyry is relatively hydrous and oxidized. The biotite monzogranite porphyry, therefore, is believed to be a relatively fertile intrusion with certain exploration potential.
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
