Xiaohu Li

• PhD
• Research Associate at Second Institute of Oceanography

Pyrite-marcasite assemblages, formed at steep physicochemical gradients in submarine hydrothermal systems, serve as valuable records of fluid evolution and ore-forming processes. However, gaps remain in our understanding of the detailed pathways of pyrite-marcasite formation and their dynamics of trace element enrichment in seafloor massive sulfide...

Polymetallic nodules, widely distributed in the deep seafloor of the Pacific Ocean, are characterized by their abundance of diverse metal elements and considerable economic value. Previous studies have suggested a partial biogenic origin of these nodules. This study investigated the role of microorganisms in nodule formation by examining biological...

Polymetallic nodules on the global seabed are an enormous resource for critical metals, while environmental impacts caused by mining activities such as sediment disturbance and plume diffusion are under evaluation. Geotechnical properties of surface sediments hosting nodules will critically impact mining operations. However, the spatial variation i...

The identification of the maturity stages of collapsed sulfide chimneys remains challenging due to alterations in their original structural and mineralogical characteristics. The trace element composition of sulfides can provide valuable information about the mineralization processes in submarine hydrothermal systems. However, the link between trac...

Polymetallic ferromanganese nodules (PMNs) in the Clarion-Clipperton Zone (CCZ) exhibit significant spatial variability in chemical composition, which complicates exploration efforts and increases associated costs. The primary factors driving this spatial variability remain unclear due to limited understanding of the growth history of these nodules...

Deep sea sedimentary mineral resources mainly include cobalt- rich crusts, polymetallic nodules and REEs- rich sediments, of which the former two are rich in cobalt, nickel, copper, rare earth elements (REEs) and other critical metal elements, and the latter is rich in medium and heavy REEs, which are potential strategic mineral resources in the fu...

Platinum-group elements (PGEs) have a strong affinity for sulfur and tend to accumulate in the deep continental crust, either concentrated within magmatic Cu-Ni-PGE deposits or dispersed throughout disseminated sulfides. However, PGE enrichment in shallow magmatic-hydrothermal systems implies an obscure link to deep sulfide destabilization, which r...

Herein, the morphological characteristics of submarine archipelagic aprons were presented for five guyots, Suda, Arnold, Lamont, Niulang, and Zhinyv, which are over 80 Ma years old and are located in the Marcus–Wake seamount group, northwestern Pacific Ocean. Nearly 28 landslide deposits were recognized using the bathymetry and backscatter intensit...

With the rapid development and wide use of fuel cells and scandium (Sc)-aluminum (Al) alloy, the demand for Sc may increase significantly in the future. Due to the lack of independent deposits, Sc is mainly derived from comprehensive utilization at present, which may cause a potential resource risk for the green economy in the future. It has been r...

REY‐rich mud, consisting of deep‐sea sediments with high concentrations of rare‐earth elements and yttrium (REY), holds significant economic potential. Many studies have been conducted on biogenic apatite, ferromanganese micronodule, and phillipsite within these deposits to ascertain the REY enrichment mechanisms. However, the knowledge of clay min...

The Clarion–Clipperton Fracture Zone of the east Pacific contains numerous shallow buried nodules that are in direct contact with pore water in sediment, providing a direct reflection of the interaction between nodules and sediment. However, research on the geochemical behavior of these shallow-buried nodules is limited. This study used laser ablat...

Understanding the relationship between sulfide chimney maturity and fluid evolution in submarine hydrothermal systems is essential for deciphering mineralogical changes, sulfur dynamics, and fluid flux over time. We investigate this link through sulfur isotopic analysis of sulfides from three maturity stages of sulfide chimneys at the Niaochao hydr...

Dehydrated fluids expelled from the serpentinised mantle in subducted slabs contribute significantly to arc magmatism and element cycling on Earth. However, the recycling mechanism of serpentinite-derived fluids at various subduction zone depths remains unclear, as does their contribution to the genesis of back-arc basin lavas. In this study, we in...

Ferromanganese nodules are a potential energy resource because of their high contents of economically interesting elements (i.e. Mn, Ni, Cu, and Zn). These are higher in diagenetic layers than in hydrogenetic layers. The study of the causes of elemental accumulation in the diagenetic layer is useful for the exploration metal-rich nodules. A diagene...

Compared with the deeply buried marine gas hydrate deposits, gas hydrates in the shallow subsurface, close to and at the seafloor, have attracted more attention owing to their concentrated distribution, high saturation, and easy access. They accumulate at relatively shallow depths <100–120 m and occur as gas hydrate-bearing mounds (also known as hy...

The highly siderophile elements (HSEs) in peridotites from the Yap Trench are investigated to understand their behavior in the subduction zone mantle, which is characterized by high melt depletion and metasomatism. Results reveal that the abundance of HSEs in Yap Trench peridotites is extremely low compared with that in oceanic peridotites from the...

The shallow seawater-hydrothermal circulation system plays a crucial role in the subseafloor mineralization of the hydrothermal field. However, its key fluid processes and impacts on the metal mobilization and sulfur cycles in the stockwork mineralization are still poorly understood. We first present the systemic variations in micro-scale trace ele...

Dehydrated fluids expelled from serpentinized mantle in the subducted slab are gradually recognised as a vital role in generating arc magmatism and element cycling in the Earth. However, it remains not clear about their recycling at various depth in subduction zones and if slab serpentinite-derived fluids contribute to the genesis of lavas from the...

The weathering processes of seafloor massive sulfide (SMS) deposits would significantly change the mineralogy and geochemistry of sulfides. The key to understanding the oxidation of SMS deposits lies in clarifying the metal mobilization during the oxidation of submarine sulfides by seawater and Fe-Si-rich hydrothermal fluids. We present the morphol...

We present major and trace element data of lava recovered from the northern Yap Trench in the western Pacific and discuss their petrogenesis and tectonic implications within the framework of interactions between the Caroline Ridge and Yap Trench. Rocks were collected from both landward and seaward trench slopes and exhibited geochemical characteris...

Carbonate recycling in subduction zones has a strong influence on arc magmatism and carbon reservoirs in the mantle. However, geochemical evidence of carbonate recycling during subduction, especially at sub-arc depths, is rare and the related process is poorly understood. In this study, we document high-Mg olivines (81–91 mol.% forsterite) with ext...

Crustal assimilation and the input of subducted sediment in a subduction zone play vital roles in generating arc and back-arc lavas along a continental margin. However, distinguishing the impacts of these two processes on lava geochemistry is not straightforward or well understood. In this paper, we present new Hf–Nd–Sr–Pb isotopic data for 20 igne...

Manganese nodules are a potential source of critical metals such as Cu, Ni, and Co and are widely distributed on the abyssal plains of the global oceans. A polymetallic nodule metallogenic belt with a heterogeneous and spatially clustered nodule distribution was recently discovered in NW Pacific inter-seamount basin (NPIB) areas. However, the geolo...

Discontinuities in the magmatic activity along a spreading ridge are usually observed in ultraslow-spreading ridges with a thick crust. However, the reasons for such melting anomaly are unknown. The Dragon Flag Supersegment between the Indomed Fault Zone (FZ) and the Gallieni FZ on the Southwest Indian Ridge (SWIR) is characterised by ultra-thick o...

Multibeam backscatter strength can be used to characterize seafloor acoustic characteristics, and classify seabed substrate types. Herein, we use acoustic reflectance data to examine the distribution of manganese nodules in deep-sea substrates in a seamount region of the Western Pacific Ocean. Based on the multibeam backscatter strength, the backsc...

This book focuses on the survey technology, post-processing technology, mapping technology and scientific application of the submarine topography and geomorphology in detail.High-resolution submarine geomorphology is a frontier branch of marine geology and marine surveying and mapping, which provides a direct basis to study the seabed surface, to u...

The Okinawa Trough (OT), is a back-arc basin where rifting is in its initial stages, and where hydrothermal fields (HTFs) have developed above terrigenous sediments and volcaniclastics layers of variable thickness. The source of ore-forming materials within the hydrothermal systems of the OT is complex, and may include seawater, magmatic rock, magm...

Electron microprobe analysis was conducted on plagioclase from the plagioclase ultraphyric basalts (PUBs) erupted on the Southwest Indian Ridge (SWIR) (51°E) to investigate the geochemical changes in order to better understand the magmatic processes occurring under ultraslow spreading ridges and to provide insights into the thermal and dynamic regi...

The nature of upper mantle is important to understand the evolution of the South China Sea (SCS); thus, we need better constrains on its mantle heterogeneity. Magma water concentration is a good indicator, but few data have been reported. However, the rarity of glass and melt inclusions and the special genesis for phenocrysts in SCS basalts present...

Magmatic sulfide formation and oxidative dissolution are effective in metal pre-enrichment and remobilization during magmatic processes, and are considered to be a prerequisite for the formation of magmatic–hydrothermal ore deposits in subduction zones. However, this sequential process and sulfide oxidation mechanism are poorly understood. In this...

The northern Lau back-arc basin (NLB) lavas display a diverse geochemical nature caused by complex geological processes in this region. Independent component (IC) analysis was applied to investigate the nature of mantle sources in the NLB, based on a compiled geochemical data set from the NLB, central-southern Lau Basin (C-SLB), Pacific and Indian...

Sulphur isotopes can be used as a powerful tool to trace fluid evolution and explore the formation of chimneys. To clarify the in situ S isotopic variations of sulphides at the micro-scale, we analyzed a sulphide chimney collected from the hydrothermal field in the East Pacific Rise 1–2° S using a sensitive high-mass-resolution ion micro-probe for...

Significant Zn isotope fractionation occurs during seafloor hydrothermal activities. Therefore, exploring variations in Zn isotope composition affected by hydrothermal fluids and oxidative processes would help to better understand hydrothermal fluid cycling and sulfide deposition on mid-ocean ridges. In this paper, the Zn isotope compositions of di...

Considerable Cu isotopic fractionation occurs during the formation of mineral deposits and the oxidative weathering processes of modern seafloor hydrothermal sulfides. This report is the first to describe Cu isotopic compositions of Curich and Zn-rich sulfides, and their oxidation products collected from hydrothermal fields along the South Mid-Atla...

Lipid biomarkers were investigated to reveal the microbial life preserved in sulfide and Si-rich chimney from the 49.6°E hydrothermal vent field. In sulfide chimney, iso-/anteiso- fatty aicd and H-shaped glycerol dialkyl glycerol teraethers(GDGTs) are the primary microbial biomarkers. In Si-rich chimney, monounsaturated fatty acid(C16:1n7,C18:1n7)...

The 15.2°S hydrothermal field is located at 15.2°S, 13.4°W within the Mid-Atlantic Ridge (MAR) and was initially discovered during Cruise DY125-22 by the Chinese expedition during R/V Dayangyihao in 2011. Here, we provide detailed mineralogical, bulk geochemical, and Sr–Pb isotopic data for massive sulfides and basalts from the 15.2°S hydrothermal...

Significant Fe isotopic fractionation occurs during the precipitation and oxidative weathering of modern seafloor hydrothermal sulfides, which has an important impact on the cycling of Fe isotopes in the ocean. This study reports the Fe-isotope compositions of whole-rock sulfides and single-mineral pyrite collected from hydrothermal fields at the M...

Shallow water hydrothermal vents are a source of heavy metals leading to their accumulation in marine organisms that manage to live under extreme environmental conditions. This is the case at Kueishantao (KST) shallow-sea vents system offshore northeast Taiwan, where the heavy metal distribution in vent fluids and ambient seawater is poorly underst...

The chemical and isotopic compositions of gases discharging from shallow-water hydrothermal vents at Kueishantao (KST, northeast Taiwan) have been studied since 2000. In this paper, we present new data gathered from 2010 to 2014. The main component is CO2 (162–882 mmol/mol), followed by N2 (33–634 mmol/mol), CH4 (18–190 mmol/mol), and H2S (b.d.l.–1...

Hydrothermal materials in deep-sea sediments provide a robust tracer to the localized hydrothermal activity at mid-ocean ridges. Major, trace and rare earth element (REE) data for surface sediments collected from the ultraslow spreading Southwest Indian Ridge are presented to examine the existence of hydrothermal component. Biogenic carbonate oozes...

It has long been recognized that magmatic fluids exsolved from the arc-like submarine magmas of immature back-arc basins can directly contribute metals such as Cu and Au to seafloor hydrothermal systems. The extent of this magmatic contribution, however, varies from basin to basin. In order to explain this variation, we make a comparative study of...

A chronological study of seamount rocks in the South China Sea basin provides a great opportunity to understand the expansion and evolution history of the sea basin. In this paper, we analyzed the 40Ar/39Ar age of trachytic samples collected from the Shuangfeng seamounts in the northwestern sub-basin of the South China Sea. The two samples yielded...

Heavy metal contamination was the main environmental problem around the Jinchang Ni–Cu mine area of Gansu, Northwest China. The concentration of heavy metals (Cr, Cu, Ni, Pb, and Zn) in various environmental mediums around the Jinchang Ni–Cu mine area were analyzed using atomic absorption spectrometry (AAS). The different chemical speciation of hea...