Polymagmatic processes at monogenetic volcanoes: insights from Baossi monogenetic lava flows, Adamawa Plateau, Cameroon Volcanic Line

  •  Anicet Tiabou    
  •  Robert Temdjim    
  •  Caroline Ngwa    
  •  Vivian Che    
  •  François Xavier Mebara    



This paper presents principally the textural and geothermometric evidence of polymagmatic activity at a monogenetic volcano along the Cameroon Volcanic Line (CVL) in a bid to contribute to the global understanding of how such volume-limited basaltic magmatic systems operate. Preliminary geochemical data presented show that the lavas are alkali basalt and basanite (SiO2: 40.42 – 47.59 wt%, MgO: 7.61 – 9.13 wt%) and are petrographically indistinguishable. They outcrop as low mounds of columnar basalts associated with sparse pyroclastic materials. The lavas are fine porphyritic with phenocrysts of olivine and clinopyroxene set in a plagioclase microlite-dominated hypocrystalline groundmass. Olivine has two distinct populations: grains that are anhedral to glomerocrystic with spinel and plagioclase inclusions and usually have resorbed margins (olivine 1); and grains that are euhedral, sometimes skeletal, with a thin and well preserved rim (olivine 2). Similarly two clinopyroxene crystal populations are recognizable: clinopyroxene grains that are resorbed, dismembered, with sieve-textured cores and irregular core-rim margins (clinopyroxene 1); and euhedral clinopyroxene grains partially enclosing olivine phenocrysts with hour glass and sector zoning (clinopyroxene 2). These textural features suggest that the eruption was caused by an influx of a fresh batch of magma (that crystallized olivine 2 and clinopyroxene 2) into a fractionated crystal mush (olivine 1 and clinopyroxene 1) in the chamber. The crystal mush was re-heated by the intruding basaltic magma resulting in a broad pre-eruption liquidus temperature of 1040 – 1156oC calculated using mineral chemistry of equilibrium olivine-clinopyroxene pairs.


Keywords: Cameroon volcanic line, geothermometry, monogenetic volcano, olivine-clinopyroxene pairs

This work is licensed under a Creative Commons Attribution 4.0 License.
  • ISSN(Print): 1916-9779
  • ISSN(Online): 1916-9787
  • Started: 2009
  • Frequency: semiannual

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