New View on the Genesis of the Bashuihe Pluton, Laoshan Granites, China: Indications from Fluid Inclusions and H–O Isotopes

Oval caves have recently been discovered in the Bashuihe granite pluton of Laoshan Mountain, China. Oval caves typically occur in alkaline granites. This study conducted microthermometry and stable isotope analysis of quartz inclusions from oval caves and host rocks from the Bashuihe pluton to recon...

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Main Authors: Huimin Liu, Zhaojun Song, Hongbo Yan, Wenyu Wang, Xinru Wang, Yifang Sun, Haonan Li
Format: Article
Language:English
Published: Wiley 2021-01-01
Series:Geofluids
Online Access:http://dx.doi.org/10.1155/2021/6655431
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author Huimin Liu
Zhaojun Song
Hongbo Yan
Wenyu Wang
Xinru Wang
Yifang Sun
Haonan Li
author_facet Huimin Liu
Zhaojun Song
Hongbo Yan
Wenyu Wang
Xinru Wang
Yifang Sun
Haonan Li
author_sort Huimin Liu
collection DOAJ
description Oval caves have recently been discovered in the Bashuihe granite pluton of Laoshan Mountain, China. Oval caves typically occur in alkaline granites. This study conducted microthermometry and stable isotope analysis of quartz inclusions from oval caves and host rocks from the Bashuihe pluton to reconstruct the diagenetic evolutionary history of the Laoshan area. The temperature measurement results indicated a homogenisation temperature range from 162.5 to 261.6°C (mean 203.9°C), a salinity range of 2.1–8.3 wt% (mean 5.07 wt%), and a density range of 0.8–0.98 g/cm3 (mean 0.90 g/cm3), indicating a low-temperature, low-salinity, and low-density fluid. The emplacement depth ranged from 2.73 km to 4.43 km, indicating medium-shallow granite. A hydrogen and oxygen isotope analysis (δD=−83.58–−67.17, δ18OH2O=0.83–0.39) revealed that the diagenetic fluids of the Bashuihe pluton represented a mixed hydrothermal solution composed of meteoric water and magmatic water. The results of a whole rock, H–O isotopes, rare earth element, and high field strength element analysis on the Laoshan alkali granites suggest significant hydrothermal activity in the late stage of magmatism. Primary oval caves in the Bashuihe pluton most likely evolved in the following sequence: fluid was enriched in the late diagenetic stage, diagenetic minerals crystallised under low temperature and pressure conditions, the crystallisation rate accelerated, and the magma condensed rapidly. Moreover, the increase in magma fluid enabled the movement and convergence of fluid. The accumulated fluid and volatiles occupied more space, and rapid magma condensation trapped the accumulated fluid and volatiles in the pluton, forming the oval granite cave. This research provides a crucial theoretical reference for the development and utilisation of underground space and engineering buildings in granite regions.
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spelling doaj-art-1fa2c9e9a0b54256b994566661c6bfb82025-02-03T06:06:30ZengWileyGeofluids1468-81151468-81232021-01-01202110.1155/2021/66554316655431New View on the Genesis of the Bashuihe Pluton, Laoshan Granites, China: Indications from Fluid Inclusions and H–O IsotopesHuimin Liu0Zhaojun Song1Hongbo Yan2Wenyu Wang3Xinru Wang4Yifang Sun5Haonan Li6College of Earth Science and Engineering, Shandong University of Science and Technology, Qingdao 266590, ChinaCollege of Earth Science and Engineering, Shandong University of Science and Technology, Qingdao 266590, ChinaCollege of Earth Science and Engineering, Shandong University of Science and Technology, Qingdao 266590, ChinaCollege of Earth Science and Engineering, Shandong University of Science and Technology, Qingdao 266590, ChinaCollege of Earth Science and Engineering, Shandong University of Science and Technology, Qingdao 266590, ChinaCollege of Earth Science and Engineering, Shandong University of Science and Technology, Qingdao 266590, ChinaCollege of Earth Science and Engineering, Shandong University of Science and Technology, Qingdao 266590, ChinaOval caves have recently been discovered in the Bashuihe granite pluton of Laoshan Mountain, China. Oval caves typically occur in alkaline granites. This study conducted microthermometry and stable isotope analysis of quartz inclusions from oval caves and host rocks from the Bashuihe pluton to reconstruct the diagenetic evolutionary history of the Laoshan area. The temperature measurement results indicated a homogenisation temperature range from 162.5 to 261.6°C (mean 203.9°C), a salinity range of 2.1–8.3 wt% (mean 5.07 wt%), and a density range of 0.8–0.98 g/cm3 (mean 0.90 g/cm3), indicating a low-temperature, low-salinity, and low-density fluid. The emplacement depth ranged from 2.73 km to 4.43 km, indicating medium-shallow granite. A hydrogen and oxygen isotope analysis (δD=−83.58–−67.17, δ18OH2O=0.83–0.39) revealed that the diagenetic fluids of the Bashuihe pluton represented a mixed hydrothermal solution composed of meteoric water and magmatic water. The results of a whole rock, H–O isotopes, rare earth element, and high field strength element analysis on the Laoshan alkali granites suggest significant hydrothermal activity in the late stage of magmatism. Primary oval caves in the Bashuihe pluton most likely evolved in the following sequence: fluid was enriched in the late diagenetic stage, diagenetic minerals crystallised under low temperature and pressure conditions, the crystallisation rate accelerated, and the magma condensed rapidly. Moreover, the increase in magma fluid enabled the movement and convergence of fluid. The accumulated fluid and volatiles occupied more space, and rapid magma condensation trapped the accumulated fluid and volatiles in the pluton, forming the oval granite cave. This research provides a crucial theoretical reference for the development and utilisation of underground space and engineering buildings in granite regions.http://dx.doi.org/10.1155/2021/6655431
spellingShingle Huimin Liu
Zhaojun Song
Hongbo Yan
Wenyu Wang
Xinru Wang
Yifang Sun
Haonan Li
New View on the Genesis of the Bashuihe Pluton, Laoshan Granites, China: Indications from Fluid Inclusions and H–O Isotopes
Geofluids
title New View on the Genesis of the Bashuihe Pluton, Laoshan Granites, China: Indications from Fluid Inclusions and H–O Isotopes
title_full New View on the Genesis of the Bashuihe Pluton, Laoshan Granites, China: Indications from Fluid Inclusions and H–O Isotopes
title_fullStr New View on the Genesis of the Bashuihe Pluton, Laoshan Granites, China: Indications from Fluid Inclusions and H–O Isotopes
title_full_unstemmed New View on the Genesis of the Bashuihe Pluton, Laoshan Granites, China: Indications from Fluid Inclusions and H–O Isotopes
title_short New View on the Genesis of the Bashuihe Pluton, Laoshan Granites, China: Indications from Fluid Inclusions and H–O Isotopes
title_sort new view on the genesis of the bashuihe pluton laoshan granites china indications from fluid inclusions and h o isotopes
url http://dx.doi.org/10.1155/2021/6655431
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