4:45 PM - 5:00 PM
[HRE12-11] Impact of the Emeishan Large Igneous Province on the Thermal Evolution of Hydrocarbon Source Rocks in the Sichuan Basin: A Review
Keywords:ELIP, Thermal evolution, Vitrinite reflectance, Paleo-heat flow
The Emeishan Large Igneous Province (ELIP), one of the largest Late Permian magmatic events globally, has profoundly reshaped the thermal evolution pathways of hydrocarbon source rocks and their hydrocarbon generation-preservation processes in the Sichuan Basin through intense thermal perturbations.Researchers systematically unveiled the spatiotemporal differential control mechanisms of the ELIP thermal event on source rock maturity evolution and hydrocarbon distribution through integrated approaches including regional geothermal background reconstruction, spatial analysis of vitrinite reflectance (Ro), dynamic thermal history modeling, and validation with typical exploration cases.
(1) The thermal perturbations from ELIP magmatism significantly altered the spatial configuration of the palaeogeothermal field in the Sichuan Basin. Geochemical and thermal history inversion analyses demonstrate that the thermal effects of the Emeishan LIP decrease progressively from southwestern Sichuan to western/southern Sichuan and further to eastern/northern regions. In the main eruption zones (southwestern Sichuan-northeastern Yunnan), superimposed magmatic-hydrothermal influences elevated palaeo-heat flow to 80-120 mW/m² - markedly exceeding background basin values (50-70 mW/m²). This thermal anomaly triggered rapid temperature increases (ΔT >80°C) within <5 Myr for Lower Permian source rocks, creating a “thermal core effect” centered on intense heat anomalies.
(2) The distribution of vitrinite reflectance (Ro) reveals pronounced spatial heterogeneity in ELIP thermal effects: ① Adjacent to the western ELIP margin (Panxi region), Lower Paleozoic source rocks exhibit elevated Ro values (3.5%–4.5%), indicating over-mature dry gas generation; ② Eastward toward the Central Sichuan Uplift, Ro decreases to 2.8%–3.2%, corresponding to high-maturity wet gas-condensate windows; ③ In eastern basin areas, stable Ro values (2.0%–2.5%) reflect limited ELIP thermal influence; ④ Northwestern basin regions show minimal thermal imprint (Ro <0.6%), remaining essentially unaffected. This zonation strongly correlates with the spatial distribution of magmatic intrusions and development intensity of hydrothermal migration pathways.
(3)Thermal history modeling demonstrates a “dual-phase” evolutionary pattern in ELIP-affected source rocks: ①Normal thermal progression (Early Permian burial heating at ~3 °C/Myr),②Pulsed thermal acceleration (Late Permian magmatic event-triggered heating >15 °C/Myr),In contrast to thermally undisturbed marginal basins, ELIP-core source rocks experienced: 30–50 Myr advancement of primary hydrocarbon generation windows, 3–5-fold enhancement of peak hydrocarbon generation rates,This thermal forcing fundamentally altered the temporal coupling between petroleum systems (generation-migration-accumulation) and structural trap formation episodes.
(4) The spatial heterogeneity of ELIP thermal effects is governed by multifactorial controls:①Magmatic intrusion scale and facies:Large-scale mafic sills (>500 m thickness) sustain conductive thermal effects for 20–30 Myr, while volcanic eruptive facies dominate short-term radiative heating, ②Hydrothermal activity extent: Deep-seated fault systems propagate thermal anomalies laterally (50–100 km) as hydrothermal conduits, ③Tectonic superposition effects: Indosinian-Yanshanian tectonic movements induce thermal overprinting-modification in ELIP-affected zones, which amplifies spatial differentiation of source rock maturity. The ELIP thermal event drives maturity differentiation in Sichuan Basin source rocks and multi-phase hydrocarbon phase evolution through spatiotemporal restructuring of paleo-geothermal fields. Thermal intensity exhibits strong coupling with magma-tectonic-fluid interactions.
This study establishes a “thermal anomaly boundary-controlled accumulation” model, providing new insights for deep/ultra-deep exploration in superimposed basins.
(1) The thermal perturbations from ELIP magmatism significantly altered the spatial configuration of the palaeogeothermal field in the Sichuan Basin. Geochemical and thermal history inversion analyses demonstrate that the thermal effects of the Emeishan LIP decrease progressively from southwestern Sichuan to western/southern Sichuan and further to eastern/northern regions. In the main eruption zones (southwestern Sichuan-northeastern Yunnan), superimposed magmatic-hydrothermal influences elevated palaeo-heat flow to 80-120 mW/m² - markedly exceeding background basin values (50-70 mW/m²). This thermal anomaly triggered rapid temperature increases (ΔT >80°C) within <5 Myr for Lower Permian source rocks, creating a “thermal core effect” centered on intense heat anomalies.
(2) The distribution of vitrinite reflectance (Ro) reveals pronounced spatial heterogeneity in ELIP thermal effects: ① Adjacent to the western ELIP margin (Panxi region), Lower Paleozoic source rocks exhibit elevated Ro values (3.5%–4.5%), indicating over-mature dry gas generation; ② Eastward toward the Central Sichuan Uplift, Ro decreases to 2.8%–3.2%, corresponding to high-maturity wet gas-condensate windows; ③ In eastern basin areas, stable Ro values (2.0%–2.5%) reflect limited ELIP thermal influence; ④ Northwestern basin regions show minimal thermal imprint (Ro <0.6%), remaining essentially unaffected. This zonation strongly correlates with the spatial distribution of magmatic intrusions and development intensity of hydrothermal migration pathways.
(3)Thermal history modeling demonstrates a “dual-phase” evolutionary pattern in ELIP-affected source rocks: ①Normal thermal progression (Early Permian burial heating at ~3 °C/Myr),②Pulsed thermal acceleration (Late Permian magmatic event-triggered heating >15 °C/Myr),In contrast to thermally undisturbed marginal basins, ELIP-core source rocks experienced: 30–50 Myr advancement of primary hydrocarbon generation windows, 3–5-fold enhancement of peak hydrocarbon generation rates,This thermal forcing fundamentally altered the temporal coupling between petroleum systems (generation-migration-accumulation) and structural trap formation episodes.
(4) The spatial heterogeneity of ELIP thermal effects is governed by multifactorial controls:①Magmatic intrusion scale and facies:Large-scale mafic sills (>500 m thickness) sustain conductive thermal effects for 20–30 Myr, while volcanic eruptive facies dominate short-term radiative heating, ②Hydrothermal activity extent: Deep-seated fault systems propagate thermal anomalies laterally (50–100 km) as hydrothermal conduits, ③Tectonic superposition effects: Indosinian-Yanshanian tectonic movements induce thermal overprinting-modification in ELIP-affected zones, which amplifies spatial differentiation of source rock maturity. The ELIP thermal event drives maturity differentiation in Sichuan Basin source rocks and multi-phase hydrocarbon phase evolution through spatiotemporal restructuring of paleo-geothermal fields. Thermal intensity exhibits strong coupling with magma-tectonic-fluid interactions.
This study establishes a “thermal anomaly boundary-controlled accumulation” model, providing new insights for deep/ultra-deep exploration in superimposed basins.