Mineralogical and Geochemical Characteristics of Al-rich Clays from the Longqi Hydrothermal Field, Southwest Indian Ridge

Kai-jun CAO; Zhong-wei WU; Xiao-ming SUN; Yan WANG; Xiao LIN

doi:10.15898/j.cnki.11-2131/td.201804040036

2018 Vol. 37, No. 6

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Article navigation > Rock and Mineral Analysis > 2018 > 37(6): 607-617

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Kai-jun CAO, Zhong-wei WU, Xiao-ming SUN, Yan WANG, Xiao LIN. Mineralogical and Geochemical Characteristics of Al-rich Clays from the Longqi Hydrothermal Field, Southwest Indian Ridge[J]. Rock and Mineral Analysis, 2018, 37(6): 607-617. doi: 10.15898/j.cnki.11-2131/td.201804040036

Citation:

Kai-jun CAO, Zhong-wei WU, Xiao-ming SUN, Yan WANG, Xiao LIN. Mineralogical and Geochemical Characteristics of Al-rich Clays from the Longqi Hydrothermal Field, Southwest Indian Ridge[J]. Rock and Mineral Analysis, 2018, 37(6): 607-617. doi: 10.15898/j.cnki.11-2131/td.201804040036

Mineralogical and Geochemical Characteristics of Al-rich Clays from the Longqi Hydrothermal Field, Southwest Indian Ridge

1.
School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou 510275, China
2.
School of Marine Sciences, Sun Yat-sen University, Guangzhou 510006, China
3.
Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, Guangzhou 510006, China
4.
South China Sea Branch, State Oceanic Administration, Guangzhou 510310, China

More Information

Corresponding author: Xiao-ming SUN, eessxm@mail.sysu.edu.cn

Received Date: 04 April 2018

Revised Date: 16 July 2018

Accepted Date: 20 July 2018

Abstract

Abstract

BACKGROUNDThe mineralogy, chemistry and crystal structure of hydrothermal clay minerals from various geologic settings have been studied to reflect the fluid-rock interaction and physico-chemical evolution of fluids in hydrothermal environments. However, clay minerals in the ultraslow-spreading Southwest Indian Ridge have received less attention. OBJECTIVESTo obtain a better understanding of the features of clay minerals and to constrain hydrothermal alteration processes in the SWIR. METHODSA fragment of massive sulfide ore with irregular-shaped breccia was collected from the Longqi hydrothermal field and studied using SEM-EDS, XRD, FT-IR, EPMA and LA-ICP-MS to determine its mineralogical and geochemical characteristics. RESULTSThe breccia sample contains disseminated micro-sized TiO₂ and is mainly composed of Al-rich dioctahedral smectite (i.e., beidellite) and amorphous opal. The total content of REE (2.43 to 43.45 μg/g) in such Al-rich, Mg-poor and Fe-poor smectite is commonly low and the REE fractionation patterns exhibit no significant Ce anomaly (1.09-1.16) but yield negative δEu values (0.31-0.53). It has been suggested that continuous ore-forming fluids (typical of low-temperature, acidicity and relatively reduced solutions) might be responsible for extensive leaching and remobilization of all elements except Al and Ti, thus promoting the formation of Al-rich smectite at the periphery of the Longqi hydrothermal system. CONCLUSIONSThe altered clay mineral and its geochemical characteristics have been studied, reflecting the pervasive development of low-temperature hydrothermal alteration at the Longqi hydrothermal field. This study provides a basis for further discussion of the fluid-rock interaction in the ultraslow-spreading SWIR.
- Southwest Indian Ridge /
- Al-rich smectite /
- beidellite /
- low-temperature hydrothermal alteration

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