GEOCHEMISTRY OF AUTHIGENIC PYRITE MINERALIZATION OF THE NAMKONSON AND FUHAN BASINS OF THE SOUTH CHINA SEA ACCORDING TO THE DATA OF VOYAGE 88 OF THE R/V «AKADEMIK LAVRENTEV»

Abstract

The relevance. Nowadays, special attention is paid to basins that are considered potential for the presence of oil and gas occurrences. In this regard, the Namkomson and Fuhan sedimentary basins (South China Sea) are of interest. They established indirect signs of deep degassing along the rift fault. The formation of oil and gas is closely related to the formation of authigenic sulfide mineralization. Therefore, more and more questions arise about the indication of manifestations of oil and gas content of provinces by associations of authigenic minerals. In this regard, the study of sulfides from continental to oceanic is still a hot topic for research around the world. The aim of this work is to investigate the geochemical features of pyrite formations from bottom sediments of the Namсonson and Fuhan sedimentary basins of the South China Sea. Methods: inductively coupled plasma mass spectrometer; determination of losses after calcination and SiO2 content was performed by gravimetry; atomic emission spectrometer with inductively coupled plasma; optical and scanning electron microscopes; X-ray diffractometry; isotope mass spectrometry. Results. The sulfide formations from this sedimentary basin are hollow tube-shaped aggregates, up to a maximum of 5 cm in length and 5 mm in diameter. Large aggregates in the form of xenomorphic clots, spheroidal formations were also found. The aggregates themselves are composed mainly of pyrite, quartz and albite are also present. Pyrite forms globules and octahedral crystals. High contents of cobalt (16,5...56,8 g/t), nickel (21,4...377 g/t) and molybdenum (20,1...117 g/t) were established in pyrite formations. The Ce anomaly is 0,90...0,93. The isotopic values of δ34S range from –32,9 to –47,0 ‰. These values and the genetic diagrams derived from them indicate a hydrothermal/diagenetic origin for the pyrite formations.

Keywords

• south china sea
• sedimentary basin
• fuhan
• namkonson
• authigenic mineralization
• pyrite formations
• petrogenic elements
• trace elements
• geochemistry