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Detrital K‐feldspar 40 Ar/ 39 Ar Ages: Source Constraints of the Lower Miocene Sandstones in the Pearl River Mouth Basin, South China Sea
Author(s) -
Zaisheng LIU,
Hesheng SHI,
Junzhang ZHU,
Huaning QIU,
Zhilin ZHANG,
Jianbing YUN
Publication year - 2012
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/j.1755-6724.2012.00667.x
Subject(s) - geology , cretaceous , detritus , feldspar , source rock , geochemistry , plateau (mathematics) , illite , zircon , paleontology , structural basin , clay minerals , quartz , mathematical analysis , mathematics
The South China Sea began to outspread in the Oligocene. A great quantity of terraneous detritus was deposited in the northern continental shelf of the sea, mostly in Pearl River Mouth Basin, which constituted the main paleo‐Pearl River Delta. The delta developed for a long geological time and formed a superimposed area. Almost all the oil and gas fields of detrital rock reservoir distribute in this delta. Thirty‐three oil sandstone core samples in the Zhujiang Formation, lower Miocene (23–16 Ma), were collected from nine wells. The illite samples with detrital K feldspar (Kfs) separated from these sandstone cores in four sub‐structural belts were analysed by the high‐precision 40 Ar/ 39 Ar laser stepwise heating technique. All 33 illite 40 Ar/ 39 Ar data consistently yielded gradually rising age spectra at the low‐temperature steps until reaching age plateaus at mid‐high temperature steps. The youngest ages corresponding to the beginning steps were interpreted as the hydrocarbon accumulation ages and the plateau ages in mid‐high temperature steps as the contributions of the detrital feldspar representing the ages of the granitic parent rocks in the provenances. The ages of the detrital feldspar from the Zhujiang Formation in the four sub‐structural belts were different: (1) the late Cretaceous ages in the Lufeng 13 fault structural belt; (2) the late Cretaceous and early Cretaceous‐Jurassic ages in the Huizhou 21 buried hill‐fault belt; (3) the Jurassic and Triassic ages in the Xijiang 24 buried hill‐fault belt; and (4) the early Cretaceous – late Jurassic ages in the Panyu 4 oil area. These detrital feldspar 40 Ar/ 39 Ar ages become younger and younger from west to east, corresponding to the age distribution of the granites in the adjacent Guangdong Province, Southern China.