Baiyun Sag has become the primary focus of deepwater exploration in the Pearl River Mouth Basin. However, its complex and high-variate geothermal characteristics have severely constrained further oil and gas exploration and resource evaluation. In this study, the present-day geothermal field and tectono-thermal evolution histories of Baiyun Sag were systematically studied based on measured rock thermal conductivity and heat generation data, borehole temperatures, low-temperature thermochronometer analyses, and geodynamic methodologies. The thermal conductivity of 251 core samples ranges from 1.131 to 4.478 W/(m·K), with an average of 2.258 W/(m·K), while the heat generation rate of 106 samples ranges from 0.868 to 1.735 μW/m³, averaging 1.499 μW/m³. The thermal conductivity in Baiyun Sag exhibits a gradual decrease from the Wenchang Formation to the Hanjiang Formation, whereas the heat generation rate decreases with depth. The present-day heat flow in Baiyun Sag ranges from 66.6 to 139.1 mW/m2, with an average of 89.7 ± 14.7 mW/m2, showing a gradual increasing trend from northwest to southeast. Formation temperature at depths of 1–5 km increases proportionally with depth. Thermal inversion, as inferred from low-temperature thermochronological data of six basement samples, reveals distinct temperature paths for each tectonic unit in Baiyun Sag. These paths are primarily linked to regional tectonic uplift-subsidence and basement heat flow variation. Geodynamic simulations further indicate two extensional events in Baiyun Sag during the Eocene and Middle Miocene, leading to a rapid increase in basement heat flow. This study systematically elucidates the present-day geothermal field characteristics and tectono-thermal evolution history of Baiyun Sag, bearing significant implications for regional tectonic evolution and future deepwater oil and gas explorations.

Rifted lake basins usually have their sedimentary filling controlled by the intensity of tectonic activities, sea level fluctuation and sediment flux. The distribution of sand bodies in these basins are also controlled by slope-break zones and paleovalley systems. It is of great significance to explore the configuration relationship between the slope break zones and paleovalley systems for oil and gas exploration in rifted lake basins. The Pearl River Mouth Basin is the most important petroliferous basin in the South China Sea. The less explored Haifeng 33 Subsag in the basin is selected to study the factors controlling the development of sedimentary systems so as to support the mapping of reservoirs and deployment of oil and gas exploration. Based on 3-D seismic data and logging data of the subsag as well as on the basis of regional structural interpretation, this paper analyzes the types and development characteristics of the slope-break zones and the paleovalleys of the Paleogene Wenchang Formation in the subsag, and clarifies the control of the slope-break zones and paleovalleys on sediment filling. The results show that there are three types of slope-break zones in the study area: fault slope-break zone, flexure slope-break zone and sedimentary slope-break zone. The paleovalleys are mainly V-shaped, U-shaped, W-shaped and single fault groove types, among which the V-shaped and U-shaped valleys are more in number and more concentrated in-plane distribution. The slope-break zones control the boundary of denudation and provenance, thus mobilizing the sediments in a certain direction for a certain distance within certain space. Different sedimentary systems are believed to be developed in different periods under the influence of these zones. Serving as transport channels, paleovalleys control the direction of sediment transport, location of sediment discharge as well as scale of depositional system. It is concluded that slope-break zones together with paleovalleys determine the types, scales, development and evolution of depositional systems.

The source rocks of the Paleogene Wenchang Formation and the Enping Formation in the Baiyun sag are complex. Although the semi-deep lacustrine, shallow lacustrine, terrigenous marine, and deltaic facies have been identified, the mechanism of organic matter enrichment is unknown, leading to long-standing disagreement about the main source rocks in the area and their potential. This study analyzed the main trace elements and the characteristics of strawberry-shaped pyrite grain size in different types of source rocks that have been drilled and analyzed the development and preservation conditions of organic matter in different types of source rocks. It revealed the organic matter enrichment mechanism of different types of source rocks in the Baiyun sag for the first time. The results show that the primary productivity level of shallow lacustrine source rocks in the Baiyun sag is high. The distribution range of strawberry-shaped pyrite grain size in the Wenchang Formation is 0. 4 14. 3 rim with a wide distribution range and an average particle size of 6. 8 rim, while the distribution range of strawberry-shaped pyrite grain size in the source rock of the Enping Formation is 4. 9-15. 9 rim with an average particle size of 8. 7 rim; the overall environment is sub-oxidation. The primary productivity level of the semi-deep lacustrine source rocks is lower than that of the shallow lacustrine source rocks, and the distribution range of the strawberry-shaped pyrite grain size is narrow, ranging from 5. 6 to 8. 0 rim with an average particle size of 5. 8 rim, which is in a sulfide-sub oxidation environment with good preservation conditions for organic matter. The primary productivity level of terrigenous marine source rocks is relatively low, the preservation conditions of organic matter are good, and they receive terrigenous nutrient inputs, resulting in the enrichment of organic matter. The deltaic source rocks received a large amount of nutrients from terrigenous clastic inputs, resulting in high sediment accumulation efficiency and rapid burial. The average grain size of strawberry-shaped pyrite is > 7. 0 rim and is characterized by euhedral pyrite in an oxidized-strongly oxidized environment with poor preservation conditions for organic matter. With a large amount of source input and accumulation efficiency, it also forms a favorable area for organic matter enrichment.

陆源营养物质输入是湖泊成油母质(细菌和藻类、浮游植物等)生长的主要外部营养源.古气候条件影响了陆源输入,湖盆水体沉积环境控制了有机质保存,因此沉积期古气候古水体条件对湖相烃源岩有机质丰度预测至关重要.针对珠江口盆地陆丰凹陷文昌组烃源岩进行环境地球化学研究,运用CIA、V/Cr、Mn/Al、Sr/Cu、Ti/Al等多种元素地球化学指标,综合恢复了陆丰凹陷文昌组沉积期古风化强度与气候温湿度、湖泊古水深、古氧相、古盐度等环境条件,揭示了古环境对文昌组烃源岩的重要控制作用为:(1)珠江口盆地文昌组时期气候温湿度与化学风化强度呈明显分段,文三段下段与文四段高强度对应高有机质含量.(2)珠江口盆地文昌组时期古水深与古氧相对有机质富集起到重要控制作用,古盐度对有机质影响不大.珠江口盆地陆丰凹陷LF-A井文四段与文三段下部烃源岩形成于化学风化较强、气候温暖湿润、营养物质供应充足、湖盆生产力高、水体较深、含氧量较低的水体环境下,有机质富集.

Following the collapse of the Yanshanian orogenic belt, mantle magma uplift, crustal stretching and thinning, and multiperiod strong magmatic hydrothermal activities occurred during the Eocene in South China. As a complete early Eocene sedimentary record, the lacustrine organic-rich mudstone of the Wenchang Formation in the western Pearl River Mouth Basin (PRMB) provides an excellent opportunity to understand the early Eocene paleoclimate, paleoenvironment, and hydrothermal activities in southern China. By analyzing the organic petrology and geochemistry, the effects of paleoclimate and hydrothermal activity on organic matter (OM) accumulation in organic-rich mudstone in the early Eocene Wenchang Formation were revealed. The bulk geochemical analyses showed that these mudstones are characterized by high OM abundances (1.73-3.20 wt%), dominated by kerogen type II and in the early oil maturity window. Additionally, maceral analyses indicated that the OM sources were mainly lacustrine algae and terrestrial higher plants. The element ratios ((Fe + Mn)/Ti), rare earth element anomalies (delta Eu* and delta Ce*) and hydrothermal indicator discrimination diagrams (Zn-Ni-Co and (Cu + Ni + Co) x 10-Fe-Mn triangular plot, etc.) jointly revealed three episodes of hydrothermal activity during early Eocene Wenchang Formation deposition. Intense hydrothermal activity not only brought abundant nutrients and improved the primary productivity of the lake but also released reducing gas via hydrothermal eruption, which further aggravated the hypoxic bottom water conditions, thus promoting the accumulation and preservation of organic matter. In addition, the elemental ratios (Sr/Cu, Rb/Sr, and SiO2/Al2O3) indicated a warm paleoclimate in the early Eocene Wenchang Formation. In the period without hydrothermal activity, the humid paleoclimate promoted the prosperity of lake algae and peripheral terrestrial plants, and the high lake level provided excellent organic matter preservation conditions. Therefore, the warm and humid paleoclimate and intermittent hydrothermal activity jointly controlled the formation of lacustrine organic-rich mudstone in the early Eocene Wenchang Formation.

The Paleogene geological framework and evolution process in the central anticline zone in the Lufeng 13 sag in Pearl River Mouth Basin is well analyzed through seismic data and drilling data, and control of tectonic evolution on hydrocarbon accumulation is also discussed. The results show that the central anticline zone in the Lufeng 13 sag develops the upper deformation layer and lower deformation layer. The "arched graben system" is developed in the upper deformation layer, and the magmatic diapir structure and flowing deformation of plastic strata is developed in the lower deformation layer. The evolution process of the central anticline zone can be divided into four stages, i.e. fault block uplifting stage, prototype stage, strengthening stage and finalization stage. The geological framework and tectonic evolution of the central anticline zone control Paleogene hydrocarbon accumulation. The Paleogene two-layer geological framework is favorable for development of structural traps and composite traps; the paleostructure highs are the direction of hydrocarbon migration, and the gravitational gliding faults are the main carrier bed for vertical hydrocarbon migration; the tectonic uplift is a key factor for reservoir diagenesis improvement and preservation of primary pores, and also controls distribution of high-quality reservoirs.

The Herenping gold deposit is a typical gold deposit in the Xuefengshan arcuate tectonic zone in the southern margin of the Yangtze Craton, and the major feature of the gold mineralisation in the zone is the varying degrees of tungsten and antimony mineralisation in the ore deposits. The Herenping gold deposit occurs in the reddish purple sandy slate in the middle section of the Madiyi Formation of the Neoproterozic Banxi Group and is controlled by the fault-fold zone associated with the Liulincha anticlinorium and F8 fault zone. However, its sources of mineralisation and relationships between hydrothermal fluids and magmatic rocks are unclear, which similar to those of many gold deposits in metasedimentary terranes in the worldwide. The mineralisation can be divided into four stages: an albite-quartz stage (I), an albite-quartz-pyrite-gold stage (II), a quartz-gold-polymetallic sulphide stage (III), and a quartz-carbonate stage (IV). The gold mineralisation occurred in albite-quartz veins in stage II and in sulphide-rich quartz veins in stage III in the deposit. A study of the fluid inclusions reveals that the homogenisation temperature and salinity were slightly higher in stage II (T-h., 186-348 degrees C; W., 5.2-17.43 wt% NaCl equiv.) than in stage III (T-h., 145-249 degrees C; W., 2.9-15.57 wt% NaCl equiv.), indicating that the temperature and salinity of the ore-forming fluid are gradually decreasing. The H-O (delta D =- 62.3 to- 53.0%o; delta(18)0 = 4.2-11.8%(0)) isotope characteristics reveals that the ore-forming fluid is a magmatic hydrothermal source. The sulphur (delta S-34,-4.8-2.0%o) isotope characteristics and the alteration mineral assemblage (sericite-chlorite-pyrite) indicates that the ore-forming fluids was reduced. The lead ((206)pb/(204)pb = 17.419-17.436, (207)pb/(204)pb = 15.519-15.535, and Pb-208/Pb-204 = 37.86-37.90) isotope characteristics reflect the ore-forming materials were likely derived from a deep magmatic source. In addition, the geochemical characteristics of albitite veins show that they are silicon rich (64.02-66.26 wt%) and significantly reduced. Notably, the Herenping gold deposit is located in the western portion of the tungsten/tin metallogenic provinces in South China, is host in epimetamorphic detrital rocks and was formed at least two stages of mineralisation; typical gold-bearing albite-quartz veins developed during the primary stage. These characteristics are consistent with those of reduced intrusion-related deposits such as the Muruntau, Kumtor and Telfer deposits. Thus, the Herenping gold deposit may be a sediment-hosted intrusion-related gold deposit. Based on the phase transition pattern from sulphide-rich quartz veins to albite-quartz veins to albitite veins with increasing depth in the deposit, we propose that reduced intrusions deep in the Herenping gold deposit could be discovered in the future, which implies the possible existence of a reduced intrusion-related gold system in the Xuefengshan arcuate tectonic zone.

陆丰凹陷是珠江口盆地重要的富生烃凹陷,古近系构造和沉积特征的南北差异性影响油气成藏和有利勘探区带的分布.始新世陆丰凹陷沉降中心由南向北迁移,其中文昌组沉积期陆丰南地区控洼断裂活动性较强,并向北依次减弱;恩平组沉积期陆丰北地区控洼断裂活动性最强,并向南依次减弱.陆丰凹陷沉积充填受构造演化控制也表现出平面迁移特征,从文昌组沉积期至恩平组沉积期,沉积中心由南往北迁移,陆丰南地区主要发育文昌组深湖泥岩,陆丰北地区则发育恩平期深湖泥岩.在构造-沉积作用的共同控制下,陆丰凹陷发育了旁生侧储式、自生自储式和下生上储式等3种典型的源储配置关系.针对陆丰凹陷构造-沉积的平面迁移特征,根据“富洼找优、差异勘探”的思路,建议在陆丰南地区深挖油区潜力,在陆丰北新区加快勘探进程,优选有利二级构造带进行整体解剖并择优钻探.