The effects of a tectonic stress regime change on crustal-scale fluid flow at the Heyuan geothermal fault system, South China

Tannock, Lisa; Herwegh, Marco; Berger, Alfons; Liu, Jie; Regenauer-Lieb, Klaus

doi:10.1016/j.tecto.2020.228399

Cited by 14 publications

(19 citation statements)

References 43 publications

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“…Epidote of sample Heyuan-1 yields an age of 108.1 ± 8.4 Ma, which is (early) Cretaceous. Since the sample is crosscut by an earliest-generation quartz vein associated with hematite (Tannock et al, 2020a;2020b), this age is consistent with the earliest movements of the Heyuan Fault.…”

Section: Geological Constraints On Epidote U-pb Agessupporting

confidence: 65%

“…The Heyuan Fault is a crustal-scale fault that formed in Mesozoic times as a low-angle normal fault, but is currently active under a transpressive regime (Tannock et al, 2020a;2020b). The footwall of this fault mainly consists of the Xinfengjiang pluton (the eastern portion of the Fogang batholith), a late Jurassic biotite granite that intruded into the basement of Proterozoic to Silurian age during the Yanshanian orogeny (Li et al, 2007;Tannock et al, 2020a;2020b). Epidote veins are located in the mylonites at the transition between undeformed granite and fault zone (Tannock et al, 2020a).…”

Section: Geological Context and Field Relationsmentioning

confidence: 99%

“…The hanging wall is composed of a quartz-sericite ultracataclasite/phyllonite in contact with a quartz reef and finally abutted by the sedimentary "Red Beds" of Cretaceous age (Tannock et al, 2020a). Since the epidote veins are either preor syn-kinematic with respect to the mylonites (Tannock et al, 2020b), we infer that the epidote veins cannot be older than the pluton itself, but they are also among the earliest structures related to the early movements of the Heyuan Fault (Tannock et al, 2020a;2020b). Epidote veins are absent in the footwall cataclasite and in the quartz reef, which formed after the mylonite.…”

Section: Geological Context and Field Relationsmentioning

confidence: 99%

“…The epidote-bearing assemblage is crosscut by quartz ± hematite veins (see Fig. 4c in Tannock et al, 2020b). Epidote is variably shaped, from elongated without preferential orientation to prismatic.…”

Section: Petrography and U-th-pb Contents Of Samples Selected For U-pmentioning

confidence: 99%

“…This might suggest a magmatic origin of epidote and consequently that epidote might have formed in the Jurassic as a magmatic mineral and that the U-Pb system was reset by ingression of fluids related to the first movements of the Heyuan Fault. However, a magmatic origin of the epidote can be ruled out based on the association of epidote with chlorite instead of biotite (the magmatic phyllosilicate stable in the Xinfengjiang pluton; Li et al, 2007;Tannock et al, 2020a;2020b), the former also consistent with the temperature of mylonitization (330 °C; Tannock et al, 2020a). Furthermore, the Th/U ratios measured in Heyuan-1 epidote are << 1, whereas the Fogang Batholithwhich comprises the Xinfengjiang plutonhas Th/U ratios >> 1 (Li et al, 2007).…”

Section: Epidote Ages As Time Of Crystallization In Low-temperature Vmentioning

confidence: 99%

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U–Pb geochronology of epidote by LA–ICP–MS as a tool for dating hydrothermal-vein formation

Peverelli

Ewing

Rubatto

et al. 2020

Preprint

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Abstract. Monoclinic epidote is a low-µ (µ = 283U / 204Pb) mineral occurring in a variety of geological environments, participating in many metamorphic reactions and stable throughout a wide range of pressure–temperature conditions. Despite containing fair amounts of U, its use as a U–Pb geochronometer has been hindered by the commonly high contents of initial Pb with isotopic compositions that cannot be assumed a priori. We present U–Pb geochronology of hydrothermal-vein epidote spanning a wide range of Pb (3.9–190 µg g−1), Th (0.009–38 µg g−1) and U (2.6–530 µg g−1) contents and with µ values between 7–510 from the Albula area (eastern Swiss Alps), from the Grimsel area (central Swiss Alps) and from the Heyuan fault (Guangdong province, China). The investigated epidote samples show appreciable fractions of initial Pb that vary to different extents. A protocol has been developed for in situ U–Pb dating of epidote by spot-analysis laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) with a magmatic allanite as primary reference material. The suitability of the protocol and the reliability of the measured isotopic ratios have been ascertained by independent measurements of 238U / 206Pb and 207Pb / 206Pb ratios respectively by quadrupole and multicollector ICP–MS applied to epidote micro-separates digested and diluted in acids. For age calculation, we used the Tera–Wasserburg (207Pb / 206Pb–238U / 206Pb) diagram, which does not require corrections for initial Pb and provides the initial 207Pb / 206Pb ratio if all intra-sample analyses are co-genetic. Petrographic and microstructural data indicate that the calculated ages date the crystallization of vein epidote from a hydrothermal fluid and that the U–Pb system was not reset to younger ages by later events. Vein epidote from the Albula area formed in the Paleocene (62.7 ± 3.0 Ma) and is related to Alpine greenschist-facies metamorphism. The Miocene (19.1 ± 4.0 Ma and 16.9 ± 3.7 Ma) epidote veins from the Grimsel area formed during the Handegg phase (22–17 Ma) of the Alpine evolution of the Aar Massif. Identical initial 207Pb / 206Pb ratios reveal homogeneity in Pb isotopic compositions of the fluid across ca. 200 m. Vein epidote from the Heyuan fault is Cretaceous in age (108.1 ± 8.4 Ma) and formed during the early movements of the fault. In situ U–Pb analyses of epidote returned reliable ages of otherwise undatable epidote-quartz veins. The Tera–Wasserburg approach has proven pivotal for in situ U–Pb dating of epidote and the decisive aspect for low age uncertainties is the variability in intra-sample initial Pb fractions.

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Section: Geological Constraints On Epidote U-pb Agessupporting

confidence: 65%

Section: Geological Context and Field Relationsmentioning

confidence: 99%

Section: Geological Context and Field Relationsmentioning

confidence: 99%

Section: Petrography and U-th-pb Contents Of Samples Selected For U-pmentioning

confidence: 99%

Section: Epidote Ages As Time Of Crystallization In Low-temperature Vmentioning

confidence: 99%

See 3 more Smart Citations

U–Pb geochronology of epidote by LA–ICP–MS as a tool for dating hydrothermal-vein formation

Peverelli

Ewing

Rubatto

et al. 2020

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

Crustal Thermo-Structure and Geothermal Implication of the Huangshadong Geothermal Field in Guangdong Province

Xiao¹,

Wang

et al. 2023

J. Earth Sci.

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Hydrogeochemistry of geothermal water in Huangshadong and adjacent areas of Guangdong province: Implications for water-rock interaction

Liu,

Wang,

et al. 2024

Geothermics

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The effects of a tectonic stress regime change on crustal-scale fluid flow at the Heyuan geothermal fault system, South China

Cited by 14 publications

References 43 publications

U–Pb geochronology of epidote by LA–ICP–MS as a tool for dating hydrothermal-vein formation

U–Pb geochronology of epidote by LA–ICP–MS as a tool for dating hydrothermal-vein formation

Crustal Thermo-Structure and Geothermal Implication of the Huangshadong Geothermal Field in Guangdong Province

Hydrogeochemistry of geothermal water in Huangshadong and adjacent areas of Guangdong province: Implications for water-rock interaction

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