| Deposit types directly related to Emeishan mantle plume |
Magmatic deposits |
Fe-Ti-V oxide deposits associated with ferromafic-ultramafic intrusions |
The formation of vanadium-titanomagnetite deposits may be related to the source area of iron-rich rocks (eclogite and pyroxenite). The source area partially melted to form iron- and titanium-rich picrite magma. During magma ascent in the channel, vanadium titanomagnetite deposits are precipitated and enriched by separation and crystallization (Song et al., 2013; Bai et al., 2019) (Figure 2) |
The deposit types are classified as follows:With the upwelling of the Emeishan mantle plume, magmatic mineralization and hydrothermal mineralization will occur during the upwelling process, and finally magmatic deposits and hydrothermal deposits are formed respectively. These deposits are called deposit types directly related to the Emeishan mantle plume |
| Cu-Ni-PGE sulfide deposits associated with ferromafic-ultramafic intrusions |
According to Wang et al. (2005), the formation of three types of Cu-Ni-PGE deposits has undergone a similar magmatic process in the open system of magmatic channels. Magmatic conduits develop along cross-linked structures formed by many strike-slip faults, and each intrusion appears to be part of a grid of connected conduits that form complex channels from the mantle to the surface (Wang et al., 2005) (Figure 3). Cu-Ni enrichment type deposit: due to crustal contamination, the magmatic sulfur in the staged magma chamber reaches saturation, resulting in immiscibility of sulfide melt and segregation enrichment. Cu-Ni-PGE enrichment type deposit: The earlier magmatic pulse melted and separated in the stage magma chamber to form sulfide melt, forming Cu-Ni enrichment mineralization, and then experienced the interaction between the late sulfur-unsaturated magma continuous pulse and the early separated sulfide melt in the stage magma chamber, forming Cu-Ni-PGE enrichment type deposit in the stage magma chamber. PGE-rich deposits: Base on the formation of Cu-Ni-PGE-rich deposits, the late sulfur-unsaturated magma melts the pre-existing sulfide melt to form PGE-rich magma, which rises to an independent space formed by strike-slip faults and accumulates ore deposits |
| volcanic rock type Fe deposits associated with volcanic exhalation sedimentation of overflow basalts |
The zircon U–Pb age of this type of iron deposit was determined to be 259.7 ± 1.2 Ma (Zeng et al., 2016), consistent with the time of activity in the ELIP (260 Ma), indicating that the formation of this type of iron deposit was directly related to the eruption and deposition of the Emeishan basalt. The mineralization is volcanic exhalation and this type of iron deposit is a volcanic rock-type iron deposit |
| Hydrothermal deposits |
Nb-Ta-Zr-REE deposits related to syenite dykes |
The formation of Nb–Ta–Zr–REE deposits can be roughly divided into the syenite vein formation and rare earth metal mineral enrichment stages. The formation process of the syenite veins is as follows: after the alkaline magma intruded into the dyke in the late Emeishan mantle plume, residual magma rose along the dyke and formed numerous syenite veins in the rock surrounding the hanging wall (gabbro) and fissures in the upper part of the dyke. At this time, rare earth metal minerals were not enriched (Wang et al., 2012). Rare earth metal minerals in Nb–Ta–Zr–REE were enriched to the greatest extent during the evolution of alkaline magma until the late magmatic hydrothermal stage, and the contents of alkali elements (mainly Na) and volatiles were high. At this time, the main ore-forming elements, such as Nb, Ta, Na, F, and other elements, formed complexes. The fluid underwent sodium metasomatism along the fissures and gaps of early rock-forming minerals, and the structure of the complexes was destroyed. Nb, Ta and other elements crystallized into well-crystallized Nb-Ta minerals at albitization sites (Wang et al., 2012). Zeng and Liu (2022) revealed the enrichment mechanism of niobium and tantalum in syenite based on an in-depth study of different types of zircons in the syenites of the Baicao, Luku, and Baima mining areas. The enrichment can be divided into four stages, as shown in Figure 4
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modern weathering crust type |
At present, modern weathering crust-type deposits include weathering crust-type REE, Sc, and Ti polymetallic and laterite-type gold deposits. 1. The modern weathering crust-type REE, Sc, and Ti polymetallic deposit occurs in the modern weathering crust of the Emeishan basalt (Liu, 2020; Zhang et al., 2021). It can be directly determined that the ore-forming material is derived from the Emeishan basalt. 2. The formation process of laterite-type gold deposits is as follows: gold-rich basaltic volcaniclastic rock was enriched in the Quaternary soil of the modern karst negative terrain under long-term weathering, denudation, and leaching (Yang et al., 2007). The ELIP provided the main mineral source for modern weathering crust-type deposits |
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The types of deposits providing mineral sources |
modern sand-ore type deposits |
Modern sand ore-type deposits are sand ore-type Nanhong agate deposits, which are distributed in the Baoshan area of Yunnan Province. The agate amygdaloid body formed in the basalt through low-temperature hydrothermal filling in the late stage of Emeishan basalt magma. After weathering, denudation, transportation, and sedimentation, the Nanhong agate deposit was deposited in Quaternary strata (Liu et al., 2018; Lu, 2018) |
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| ancient weathering crust type |
Paleo-weathering crust-type deposits are lateritic iron deposits distributed in the Liupanshui–Weining area of the Guizhou Province. They were produced in the purple-red iron clay paleo-weathering crust of the Emeishan basalt. The floor of the ore layer is basalt and the roof is aluminum mudstone from the Xuanwei Formation. The U–Pb isotopic age of detrital zircons proves that the provenance is the Emeishan basalt (Meng et al., 2015). Ore-controlling factors include the vertical uplift of ancient terrain caused by the upwelling of the Emeishan mantle plume (Xu et al., 2017) and the weathering and denudation of basalt under hot and humid climate conditions (Zhou et al., 1986) |
| ancient weathering crust-sedimentary type |
Ancient weathering crust–sedimentary deposits are Nb–Sc–Ti–Ga–Zr–V–REE polymetallic deposits occurring at the bottom of the Xuanwei Formation.Many scholars believe that its source is mainly derived from Emeishan high-titanium basalt (Mclennan et al., 1993), and its mineralization is mainly weathering leaching and sedimentation (Du et al., 2019; Chen et al., 2020; Tian et al., 2021b; Dai et al., 2014) |
| sedimentary type |
The sedimentary deposits include sedimentary bauxite, sedimentary conglomerate-type Nanhong agate, sedimentary “Madouzi type” copper, sedimentary pyrite, and sedimentary sand shale-type copper deposits. 1. Based on petrogeochemical and U–Pb zircon geochronological evidence, Zhang et al. (2022a) concluded that the Emeishan basalt and volcanic ash from the ELIP provided the main sources for the formation of the bauxite deposits. 2. The provenance of the sedimentary conglomerate-type Nanhong agate deposit is the primary agate. The formation process of the primary agate is: the siliceous hydrothermal fluid in the Emeishan basalt is filled in the pores or fissures of the basalt in the late magma, forming the almond-shaped cryptocrystalline quartz (primary agate) (Liu et al., 2018). 3. The sedimentary ‘Madouzi’ copper deposit is derived from the bottom of the Xuanwei Formation. Wang et al. (2011) confirmed that its provenance is the Emeishan basalt. Its formation process is the weathering and leaching of Emeishan basalt with a high copper background value, and copper migrates to water body. In a favorable lake or swamp environment, chalcocite and bornite are formed with sediment deposition. Later, through hydrothermal metasomatism and superposition, chalcopyrite was further enriched and formed, and finally, the ‘Madouzi’ copper deposit was formed (Wang et al., 2011). 4. The sedimentary pyrite deposit occurs at the bottom of the Upper Permian Longtan Formation and above the limestone denudation surface of the Middle Permian Maokou Formation. Iron in pyrite is mainly derived from the weathering of mafic minerals, such as pyroxene, in the Emeishan basalt. After the iron is resolved, Fe2+ is transported to the reducing environment, and Fe2+and HS−combine to form pyrite (Yang et al., 2007). 5. Sedimentary sand shale-type copper deposits are distributed in Muchuan, Mabian, Pingshan, and other places in Sichuan. Copper ore bodies mainly occur in gray-green clay rock and siltstone at the bottom of the Feixianguan Formation. Rock geochemistry and detrital zircon U–Pb geochronology revealed that the provenance is the high-titanium basalt with a high copper background value (Zhang et al., 2006; Zhang et al., 2019). The metallogenic model is as follows: in the Early Triassic, the Emeishan basalt in Kangdian ancient land was weathered and eroded, and the copper in the basalt was transported to the tidal flat subfacies and intertidal mixed flat microfacies, representing a relatively quiet low-energy environment conducive for sedimentary mineralization |
| Deposit types indirectly related to Emeishan mantle plume |
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hydrothermal type |
Three types of hydrothermal deposits can be observed: basaltic copper deposits, Carlin-type gold deposits, and antimony–gold deposits in Dachang, Qinglong, and Guizhou. 1. Basalt copper deposits were mainly produced at the top of the Emeishan basalt. Natural copper minerals are sporadically distributed in basalts and can also be found in olivine phenocrysts of picrites (Zhang et al., 2006), indicating that copper was initially enriched during the formation of the Emeishan basalts. Zhu (2005) obtained a metallogenic age of 228–226 Ma, which shows that the metallogenic age is notably younger than the formation time of the ELIP. Notably, this type of deposit is further enriched and mineralized by the later hydrothermal superposition transformation. 2. Carlin-type gold deposits related to the ELIP are distributed in the Youjiang Basin at the western margin of the Yangtze Block.In recent years, Zhu et al. (2020) proposed that the Emeishan basaltic magma formed a thick gold-rich cumulate through fractional crystallization in the lower crust, and the gold in the gold-rich cumulate was activated and migrated to sedimentary rocks by the later hydrothermal activity. Zhang et al. (2006) and Tao et al. (Tao et al., 2007) found native gold in picrite olivine phenocrysts, and rocks of the ELIP, providing solid evidence for the existence of gold-rich rhyolite. The dating results show that Carlin-type gold deposits in the Youjiang Basin were formed between ∼235 and 200 Ma and ∼150–130 Ma (Hu et al., 2017), notably later than the time of activity of the Emeishan mantle plume (∼260 Ma). The formation age of Carlin-type gold deposits in the Youjiang Basin is consistent with the subduction event of the Paleo-Pacific (∼235–155 Ma) and Neo-Tethys (∼140–115 Ma) oceanic crust. Notably, Carlin-type gold deposits were formed in the back-arc extension environment caused by oceanic crust subduction. After the formation of gold-rich cumulates at ∼260 Ma, the late magmatic hydrothermal activity related to the oceanic subduction event activated the gold in gold-rich cumulates and migrated along the deep fault to the ore-bearing wall rock, precipitating mineralization.The Carlin-type gold mineralization model in the Youjiang basin is shown in Figure 5. 3. The Dachang antimony and gold ore bodies in Qinglong, Guizhou, occur in a set of siliceous altered rocks—“Dachang layer”—above the limestone of the Middle Permian Maokou Formation and underneath the Emeishan basalt (Chen et al., 2018). In the Middle–Late Permian, the Qinglong area was a shallow sea environment, which was covered by the Emeishan continental overflow basalt. Simultaneously, a large number of volcanic eruptions and hot water jet sedimentation occurred along tensile faults, resulting in the deposition of many “Dachang layer” pyroclastic rocks. Sb and Au elements were initially enriched in the “Dachang layer” (Du et al., 2020). Li (2020) obtained a mineralization age ranging from 125.2 to 148 Ma, younger than that of the ELIP, indicating that this type of deposit was formed by the preliminary enrichment of ore-forming elements in the ELIP and by the subsequent Yanshanian hydrothermal transformation (Figure 6) |
After the end of the upwelling of the Emeishan mantle plume, after a certain period of time, the upwelling event of the Emeishan mantle plume provides the ore-forming material source, ore-transporting channel and ore-forming space for the deposit. These deposits are called deposit types indirectly related to the Emeishan mantle plume |
| types of ore deposits providing ore transport channels |
REE deposits of carbonatite-syenite complex in Panxi area |
Carbonatite–syenite complex-type REE deposits are distributed in the Cenozoic Panxi rare earth metallogenic belt. Although the Cenozoic Panxi rare earth metallogenic belt was located in the Panxi ancient rift, its main ore-controlling structure was the strike-slip fault produced by the India–Asia continental collision. Although the Panxi ancient rift did not directly control the Cenozoic Panxi rare earth metallogenic belt, the ancient deep fault formed by the upwelling of the Emeishan mantle plume, close to the Panxi ancient rift, was activated by the strike-slip fault caused by the collision of the Indian–Asian continent, promoting the emplacement of the Cenozoic carbonate–alkaline complex.Therefore, the ancient deep fault developed in the Panxi ancient rift provided a congenitally advantageous ore transport channel for the intrusion of carbonate magma along the Cenozoic strike-slip fault. The upwelling of the Emeishan mantle plume provided an ore transport channel for rare earth deposits in the Cenozoic Panxi area, which indirectly restricted the mineralization |
| oil and gas deposits |
The provision of ore transport channels for oil and gas deposits is mainly reflected in the fault system formed by the rise of the Emeishan mantle plume, which reflects the correlation between source rocks and reservoirs (Ma et al., 2019) |
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deposit types providing ore-forming space |
sedimentary coal-copper-rhenium-molybdenum deposits in the Panxi rift |
Xu et al. (2001) confirmed that the Panxi paleo-rift at the southwestern margin of the Yangtze Block is the product of mantle plume activity in the Emeishan Block. The sedimentary rock layer in the Panxi ancient rift basin is thick and contains numerous minerals. Examples include the coal deposits in the Upper Triassic Daqiaodi Formation, copper, rhenium, and molybdenum polymetallic deposits in the middle and lower part of the Lower Cretaceous Feitianshan Formation (K1
f) (Hao et al., 2021), and sedimentary sandstone-type copper deposits in the bottom glutenite of the Upper Cretaceous Xiaoba Formation (K2
x). The Panxi ancient rift provided metallogenic space for these deposits |
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| oil and gas deposits |
The constraints of the Emeishan mantle plume on oil and gas reservoirs are reflected in the following aspects: 1. Volcanic rocks in the ELIP serve as good porous volcaniclastic reservoirs. During 2018–2019, explosive- and overflow-phase porous volcaniclastic rock reservoirs and the acquisition of industrial gas flow in the western Sichuan Basin were discovered (Ma et al., 2019; Yang et al., 2007). 2. The thermal effect of the Emeishan mantle plume promotes the maturity of organic matter and forms high-quality source rocks. The inversion results of ELIP formation temperature showed that the magma latent temperature of the ELIP reached 1,550°C (Xu et al., 2001). Zhu et al. (2010) reported that the Sichuan Basin exhibited a heat flow peak at ∼259 Ma, and the Emeishan basalt eruption area or concealed basalt distribution area was confirmed to have a high heat flow. The significant heat baking of the Emeishan slow column promoted the hydrocarbon generation and expulsion of the source rocks of the Cambrian Qiongzhusi Formation (Zhu et al., 2010; Wang et al., 2021), which is consistent with the ELIP in terms of the spatiotemporal distribution. 3. The uplift of the Emeishan mantle plume controlled the distribution of Middle Permian beach facies reservoirs. The upwelling of the Emeishan mantle plume caused the large-scale and longitudinal kilometer-level uplift of the paleotopography, controlled the rise and fall of the sea level, governed the distribution of sedimentary facies belts, and formed a gentle slope carbonate platform sedimentary pattern (high southwest and low northeast). Beach facies deposits were widely developed in the Qixia and Maokou formations, which created good conditions for subsequent hydrocarbon accumulation (Zhang et al., 2011). 4. The limestone of the Middle Permian Maokou Formation that was transformed by the Emeishan mantle plume became a karst reservoir. Recent oil and gas exploration results showed that the Middle Permian Maokou Formation is a high-quality karst reservoir (He et al., 2004). He et al. (2005) reported that the upwelling of the Emeishan mantle plume caused the limestone of the Maokou Formation to be uplifted into land and subjected to denudation and supergene karst transformation (Zhang et al., 2020), making the limestone of the Maokou Formation a karst reservoir. 5. The upwelling of the Emeishan mantle plume indirectly controlled the formation of sedimentary caps and reservoirs in the Xuanwei, Longtan, Wujiaping, and Feixianguan formations overlying the Emeishan basalt. The influence model of the Emeishan mantle plume on oil and gas deposition is shown in Figure 7. |