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Unravelling an allochthonous, subaqueously deposited volcanic-epiclastic to subaerial andesitic lava assemblage in Hong Kong; age, stratigraphy and provenance studies of the Middle Jurassic Tuen Mun Formation

R. J. Sewell, K. W. F. So, D. L. K. Tang and Andrew Carter
Unravelling an allochthonous, subaqueously deposited volcanic-epiclastic to subaerial andesitic lava assemblage in Hong Kong; age, stratigraphy and provenance studies of the Middle Jurassic Tuen Mun Formation
Journal of the Geological Society of London (April 2017) 174 (5): 913-928

Abstract

The Middle Jurassic Tuen Mun Formation, Hong Kong, is a fault-bounded block of rare andesitic and related rocks that preserve a snapshot of the developing SE China continental arc system during the late Mesozoic. The forearc depositional setting is considered to have been dominated by an emergent andesitic volcanic massif, which shows a transition to a fluvial-dominated volcanic plain, and then to an offshore marine environment. The youngest laser ablation inductively coupled plasma mass spectrometry U-Pb detrital zircon ages obtained from the three packages define a coherent group (n = 396; MSWD = 1.8) suggesting a maximum depositional age of 169.5 + or - 0.3 Ma. The dominance of large euhedral and concentrically zoned zircons reflects a common volcanic provenance. Hf isotope data (epsilon (sub Hf) (t) = 0 to -11) on the youngest representative zircon grains imply derivation of magmas from dominantly recycled crustal sources. The detrital zircon age signatures and Hf isotope data show no indication of magmatic interaction with adjacent late Palaeozoic and Early to Middle Jurassic sedimentary rocks, or Middle Jurassic to Early Cretaceous magmatic rocks of Hong Kong. On the basis of the structural, zircon age and isotope data, the Tuen Mun Formation is interpreted to be an allochthonous block, emplaced in the Hong Kong region during the late Middle Jurassic. Supplementary material: A full dataset of U-Pb dating and Hf isotope analysis of detrital zircons, stratigraphic drillhole logs and a description of the terminology used in this paper are available at https://doi.org/10.6084/m9.figshare.c.3736972


ISSN: 0016-7649
EISSN: 2041-479X
Coden: JGSLAS
Serial Title: Journal of the Geological Society of London
Serial Volume: 174
Serial Issue: 5
Title: Unravelling an allochthonous, subaqueously deposited volcanic-epiclastic to subaerial andesitic lava assemblage in Hong Kong; age, stratigraphy and provenance studies of the Middle Jurassic Tuen Mun Formation
Affiliation: Hong Kong Geological Survey, Department of Civil Engineering and Development, Hong Kong, China
Pages: 913-928
Published: 20170428
Text Language: English
Publisher: Geological Society of London, London, United Kingdom
References: 64
Accession Number: 2017-039864
Categories: StratigraphyIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables, geol. sketch map
N22°22'60" - N22°28'30", E113°57'18" - E114°00'30"
Secondary Affiliation: University of London, Birbeck College, GBR, United Kingdom
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 201722
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