Early Neoproterozoic (~850Ma) back-arc basin in the Central Jiangnan Orogen (Eastern South China) : Geochronological and petrogenetic constraints from meta-basalts

Yuzhi ZHANG, Yuejun WANG*, Hongyan GENG, Yanhua ZHANG, Weiming FAN, Hong ZHONG

*Corresponding author for this work

Research output: Journal PublicationsJournal Article (refereed)Researchpeer-review

101 Citations (Scopus)

Abstract

The Neoproterozoic mafic rocks of the Jiangnan Orogen in South China provide a critical geological record for unraveling regional tectonic history and testing different tectonic models. However, the geochronology, geochemistry and petrogenesis of >835Ma mafic igneous rocks in the Central and Southwestern Jiangnan Orogen have not been well reported so far, in contrast to the extensive study of such rocks in the Eastern Jiangnan Orogen. An integrated study of geochronology and geochemistry has been carried out for the basaltic rocks from NE Hunan and NW Jiangxi Provinces of the Central Jiangnan Orogen. SHRIMP, SIMS and LA-ICP-MS zircon U-Pb dating of three mafic samples yielded zircon U-Pb ages of 860±20Ma, 838±12Ma and 847±18Ma, respectively. This provides evidence for the development of early Neoproterozoic (~850Ma) mafic lava along the Central Jiangnan Orogen. SiO2 ranges from 49.43wt% to 52.07wt% and MgO from 7.36wt% to 9.04wt% with mg-number of 68-57. Their chondrite-normalized REE patterns exhibit a left-sloping pattern with more depleted LREEs relative to HREEs. On the N-MORB-normalized multi-element patterns, they are characterized by enriched highly incompatible elements, depleted moderately incompatible elements relative to those in N-MORB, insignificant Nb-Ta depletion and remarkably positive Sr and weakly negative Ti anomalies, resembling those of modern Eastern Lau back-arc basin basalts. In addition, these rocks have positive εNd(t) values of 1.30-9.36 with initial 87Sr/86Sr ratios in the range of 0.70796-0.71126. The geochemical characteristics above indicate an origination of the MORB-like source modified by the flux of the slab-derived fluid and input of the recycled sediment-derived melt. This finding, together with other geological observations, suggests that the mafic rocks in the Central Jiangnan Orogen might be formed in a back-arc basin in the eastern SCB. In conjunction with other data, it is inferred that the closure of the back-arc basin along the Central Jiangnan Orogen is contemporaneous with that in the Fuchuan area.

Original languageEnglish
Pages (from-to)325-342
Number of pages18
JournalPrecambrian Research
Volume231
Early online date29 Mar 2013
DOIs
Publication statusPublished - Jul 2013
Externally publishedYes

Fingerprint

mafic rock
mid-ocean ridge basalt
basalt
Rocks
geochronology
Geochronology
zircon
geochemistry
basin
Geochemistry
rock
Tectonics
tectonics
geological record
petrogenesis
chondrite
lava
igneous rock
slab
Igneous rocks

Keywords

  • Back-arc basin
  • Central Jiangnan Orogen
  • Early Neoproterozoic time
  • MORB source with arc-like signatures
  • Zircon U-Pb geochronology

Cite this

@article{53687788c8eb41fe9fba0c1fea04ebe4,
title = "Early Neoproterozoic (~850Ma) back-arc basin in the Central Jiangnan Orogen (Eastern South China) : Geochronological and petrogenetic constraints from meta-basalts",
abstract = "The Neoproterozoic mafic rocks of the Jiangnan Orogen in South China provide a critical geological record for unraveling regional tectonic history and testing different tectonic models. However, the geochronology, geochemistry and petrogenesis of >835Ma mafic igneous rocks in the Central and Southwestern Jiangnan Orogen have not been well reported so far, in contrast to the extensive study of such rocks in the Eastern Jiangnan Orogen. An integrated study of geochronology and geochemistry has been carried out for the basaltic rocks from NE Hunan and NW Jiangxi Provinces of the Central Jiangnan Orogen. SHRIMP, SIMS and LA-ICP-MS zircon U-Pb dating of three mafic samples yielded zircon U-Pb ages of 860±20Ma, 838±12Ma and 847±18Ma, respectively. This provides evidence for the development of early Neoproterozoic (~850Ma) mafic lava along the Central Jiangnan Orogen. SiO2 ranges from 49.43wt{\%} to 52.07wt{\%} and MgO from 7.36wt{\%} to 9.04wt{\%} with mg-number of 68-57. Their chondrite-normalized REE patterns exhibit a left-sloping pattern with more depleted LREEs relative to HREEs. On the N-MORB-normalized multi-element patterns, they are characterized by enriched highly incompatible elements, depleted moderately incompatible elements relative to those in N-MORB, insignificant Nb-Ta depletion and remarkably positive Sr and weakly negative Ti anomalies, resembling those of modern Eastern Lau back-arc basin basalts. In addition, these rocks have positive εNd(t) values of 1.30-9.36 with initial 87Sr/86Sr ratios in the range of 0.70796-0.71126. The geochemical characteristics above indicate an origination of the MORB-like source modified by the flux of the slab-derived fluid and input of the recycled sediment-derived melt. This finding, together with other geological observations, suggests that the mafic rocks in the Central Jiangnan Orogen might be formed in a back-arc basin in the eastern SCB. In conjunction with other data, it is inferred that the closure of the back-arc basin along the Central Jiangnan Orogen is contemporaneous with that in the Fuchuan area.",
keywords = "Back-arc basin, Central Jiangnan Orogen, Early Neoproterozoic time, MORB source with arc-like signatures, Zircon U-Pb geochronology",
author = "Yuzhi ZHANG and Yuejun WANG and Hongyan GENG and Yanhua ZHANG and Weiming FAN and Hong ZHONG",
year = "2013",
month = "7",
doi = "10.1016/j.precamres.2013.03.016",
language = "English",
volume = "231",
pages = "325--342",
journal = "Precambrian Research",
issn = "0301-9268",
publisher = "Elsevier",

}

Early Neoproterozoic (~850Ma) back-arc basin in the Central Jiangnan Orogen (Eastern South China) : Geochronological and petrogenetic constraints from meta-basalts. / ZHANG, Yuzhi; WANG, Yuejun; GENG, Hongyan; ZHANG, Yanhua; FAN, Weiming; ZHONG, Hong.

In: Precambrian Research, Vol. 231, 07.2013, p. 325-342.

Research output: Journal PublicationsJournal Article (refereed)Researchpeer-review

TY - JOUR

T1 - Early Neoproterozoic (~850Ma) back-arc basin in the Central Jiangnan Orogen (Eastern South China) : Geochronological and petrogenetic constraints from meta-basalts

AU - ZHANG, Yuzhi

AU - WANG, Yuejun

AU - GENG, Hongyan

AU - ZHANG, Yanhua

AU - FAN, Weiming

AU - ZHONG, Hong

PY - 2013/7

Y1 - 2013/7

N2 - The Neoproterozoic mafic rocks of the Jiangnan Orogen in South China provide a critical geological record for unraveling regional tectonic history and testing different tectonic models. However, the geochronology, geochemistry and petrogenesis of >835Ma mafic igneous rocks in the Central and Southwestern Jiangnan Orogen have not been well reported so far, in contrast to the extensive study of such rocks in the Eastern Jiangnan Orogen. An integrated study of geochronology and geochemistry has been carried out for the basaltic rocks from NE Hunan and NW Jiangxi Provinces of the Central Jiangnan Orogen. SHRIMP, SIMS and LA-ICP-MS zircon U-Pb dating of three mafic samples yielded zircon U-Pb ages of 860±20Ma, 838±12Ma and 847±18Ma, respectively. This provides evidence for the development of early Neoproterozoic (~850Ma) mafic lava along the Central Jiangnan Orogen. SiO2 ranges from 49.43wt% to 52.07wt% and MgO from 7.36wt% to 9.04wt% with mg-number of 68-57. Their chondrite-normalized REE patterns exhibit a left-sloping pattern with more depleted LREEs relative to HREEs. On the N-MORB-normalized multi-element patterns, they are characterized by enriched highly incompatible elements, depleted moderately incompatible elements relative to those in N-MORB, insignificant Nb-Ta depletion and remarkably positive Sr and weakly negative Ti anomalies, resembling those of modern Eastern Lau back-arc basin basalts. In addition, these rocks have positive εNd(t) values of 1.30-9.36 with initial 87Sr/86Sr ratios in the range of 0.70796-0.71126. The geochemical characteristics above indicate an origination of the MORB-like source modified by the flux of the slab-derived fluid and input of the recycled sediment-derived melt. This finding, together with other geological observations, suggests that the mafic rocks in the Central Jiangnan Orogen might be formed in a back-arc basin in the eastern SCB. In conjunction with other data, it is inferred that the closure of the back-arc basin along the Central Jiangnan Orogen is contemporaneous with that in the Fuchuan area.

AB - The Neoproterozoic mafic rocks of the Jiangnan Orogen in South China provide a critical geological record for unraveling regional tectonic history and testing different tectonic models. However, the geochronology, geochemistry and petrogenesis of >835Ma mafic igneous rocks in the Central and Southwestern Jiangnan Orogen have not been well reported so far, in contrast to the extensive study of such rocks in the Eastern Jiangnan Orogen. An integrated study of geochronology and geochemistry has been carried out for the basaltic rocks from NE Hunan and NW Jiangxi Provinces of the Central Jiangnan Orogen. SHRIMP, SIMS and LA-ICP-MS zircon U-Pb dating of three mafic samples yielded zircon U-Pb ages of 860±20Ma, 838±12Ma and 847±18Ma, respectively. This provides evidence for the development of early Neoproterozoic (~850Ma) mafic lava along the Central Jiangnan Orogen. SiO2 ranges from 49.43wt% to 52.07wt% and MgO from 7.36wt% to 9.04wt% with mg-number of 68-57. Their chondrite-normalized REE patterns exhibit a left-sloping pattern with more depleted LREEs relative to HREEs. On the N-MORB-normalized multi-element patterns, they are characterized by enriched highly incompatible elements, depleted moderately incompatible elements relative to those in N-MORB, insignificant Nb-Ta depletion and remarkably positive Sr and weakly negative Ti anomalies, resembling those of modern Eastern Lau back-arc basin basalts. In addition, these rocks have positive εNd(t) values of 1.30-9.36 with initial 87Sr/86Sr ratios in the range of 0.70796-0.71126. The geochemical characteristics above indicate an origination of the MORB-like source modified by the flux of the slab-derived fluid and input of the recycled sediment-derived melt. This finding, together with other geological observations, suggests that the mafic rocks in the Central Jiangnan Orogen might be formed in a back-arc basin in the eastern SCB. In conjunction with other data, it is inferred that the closure of the back-arc basin along the Central Jiangnan Orogen is contemporaneous with that in the Fuchuan area.

KW - Back-arc basin

KW - Central Jiangnan Orogen

KW - Early Neoproterozoic time

KW - MORB source with arc-like signatures

KW - Zircon U-Pb geochronology

UR - http://www.scopus.com/inward/record.url?scp=84877337007&partnerID=8YFLogxK

U2 - 10.1016/j.precamres.2013.03.016

DO - 10.1016/j.precamres.2013.03.016

M3 - Journal Article (refereed)

VL - 231

SP - 325

EP - 342

JO - Precambrian Research

JF - Precambrian Research

SN - 0301-9268

ER -