Paleogene igneous intrusion and its effect on thermal maturity of organic-rich mudstones in the Beibuwan Basin, South China Sea

Liu, Entao, Wang, Hua, Uysal, I. Tonguç, Zhao, Jian-xin, Wang, Xuan-Ce, Feng, Yuexing and Pan, Songqi (2017) Paleogene igneous intrusion and its effect on thermal maturity of organic-rich mudstones in the Beibuwan Basin, South China Sea. Marine and Petroleum Geology, 86 733-750. doi:10.1016/j.marpetgeo.2017.06.026


Author Liu, Entao
Wang, Hua
Uysal, I. Tonguç
Zhao, Jian-xin
Wang, Xuan-Ce
Feng, Yuexing
Pan, Songqi
Title Paleogene igneous intrusion and its effect on thermal maturity of organic-rich mudstones in the Beibuwan Basin, South China Sea
Journal name Marine and Petroleum Geology   Check publisher's open access policy
ISSN 0264-8172
1873-4073
Publication date 2017-09-01
Sub-type Article (original research)
DOI 10.1016/j.marpetgeo.2017.06.026
Open Access Status Not yet assessed
Volume 86
Start page 733
End page 750
Total pages 18
Place of publication London, United Kingdom
Publisher Elsevier
Language eng
Subject 1910 Oceanography
1908 Geophysics
1907 Geology
1905 Economic Geology
1913 Stratigraphy
Abstract The seismic, drilling and logging data reveal that a large-scale igneous intrusion with a width of 14 Km and a maximum thickness of 170 m intruded within the Paleogene Liushagang Formation in the Fushan Depression, Beibuwan Basin, South China Sea (SCS). In this study, we report the geochemistry and Sr-Nd-Pb-Hf isotopic compositions of the igneous rocks, and evaluate the thermal effect induced by this large-scale igneous intrusion on the host rocks. The analyzed igneous samples exhibit strong enrichment in light rare earth elements (LREE) and large-ion lithophile elements (LILE), having characteristics similar to intra-plate oceanic island basalts (OIB). The Sr-Nd-Pb-Hf isotopic data display narrow ranges (e.g. Sr/Sr = 0.7042–0.7044, Nd/Nd = 0.5128–0.5129, Pb/Pb = 18.90–18.94, εHf(t) = +7.56∼+9.60). Geochemical and isotopic compositions suggest a mixed mantle source between depleted mid-ocean-ridge-basalt (MORB) mantle (DMM)-like mantle and enriched mantle type II (EMII, possibly the Hainan mantle plume). Vitrinite reflectance values, major mineralogical changes together with a maturity-related biomarker [Ts/(Ts + Tm)] all reveal significant thermal effect induced by the igneous intrusion. Vitrinite reflectance values of the host rock are up to 2.5% in the intrusion region, whereas lower reflectance values (0.62–0.73%) occur in the unaffected area of the same strata. Moreover, our results suggest that the host rocks above the igneous intrusion are characterised by higher maturity than below, which should be attributed to the different behavior of hydrothermal fluids. These observations suggest that the thermal effect of large-scale thick igneous intrusions is much more intense than that of thin igneous intrusions, and the behavior of hydrothermal fluids induced by magmatic intrusive events should be a critical impact factor during heat transfer process.
Keyword Beibuwan Basin
Geochemistry
Igneous intrusion
South China Sea
Sr-Nd-Pb-Hf
Thermal effect
Q-Index Code C1
Q-Index Status Provisional Code
Grant ID 41472084
FT140100826
G1323531566
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
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