TY - JOUR
T1 - Physical and geochemical reconstruction of a 2.35–2.1 Ga volcanic arc (Toumodi Greenstone Belt, Ivory Coast, West Africa)
AU - Hayman, P. C.
AU - Bolz, P.
AU - Senyah, G.
AU - Tegan, E.
AU - Denyszyn, S.
AU - Murphy, D. T.
AU - Jessell, M. W.
N1 - Funding Information:
This research was funded through AMIRA project P934B – West African Exploration Initiative – Stage 3, under the Volcanology Module 1.2B. We firstly thank all the local people from around Toumodi for their generosity granting us land access. We also thank Toro Gold, Newcrest and Perseus Mining for access to drill core and as hosts, with special thanks deserved for Fulbert Narma Beka, for his knowledge of the local geology and showing us some key outcrops. In a similar manner, we are thankful to Dr Inza Coulibaly for his geological knowledge of the region and for field assistance. Prof Nico Thébaud is thanked for supplying a sample for geochronology. We thank Dr Nils Lenhardt and an anonymous reviewer for helpful comments, and Prof Wilson Teixeira for editorial handling. Most analytical work was enabled by use of the Central Analytical Research Facility (CARF) at the Queensland University of Technology (QUT), especially by help from Karine Harumi Moromizato and Prof Charlotte Allen. PCH is grateful for support of his wife, Dr Sahereh Aivazpourporgou, who looked after two young boys during field work.
Publisher Copyright:
© 2023 The Author(s)
PY - 2023/6/1
Y1 - 2023/6/1
N2 - This study reconstructs the evolution of one of the oldest Paleoproterozoic arcs, which formed shortly after a period of momentous change when the Earth transitioned out of the Archean. We present new stratigraphic, geochemical and geochronological data of the Toumodi Greenstone Belt (Ivory Coast, West Africa) integrated with local and regional data to better constrain its construction and evolution. The belt consists of four main stratigraphic events: [1] A ca. 2345 Ma tholeiitic sequence formed on the sea floor far from any landmass. This juvenile crust is the oldest Birimian supracrustal sequence known and represents either a dismembered oceanic plateau or ridge basalt; [2] Nascent arc formation (ca. 2220–2160 Ma) developed initially in a subaqueous environment and transitions into emergent volcanic centres. Near Toumodi, most deposits consist of volcaniclastic debris emplaced in subaerial to shallow-water environments, but also include minor pyroclastic vent-proximal deposits. Magmas for this event are mainly basaltic andesite to andesite and are enriched in LILE and have negative Nb, Ta and Ti signatures, all of which are consistent with water-fluxed melting typical of arc magmatism. Inherited zircons and mafic xenocrysts/xenoliths together reflect the older history and nature of underlying mid- to lower-crustal rocks, [3] An intra-arc rifting-event marked by a unconformity between events 2 and 4 the correlation with pillowed tholeiitic basalts; and [4] Construction of a mature arc (ca. 2150–2100 Ma) that consists of emergent dacitic volcanic centres and more distal volcaniclastic sediments, and overlain by post-magmatic sedimentation and red-bed formation (ca. 2100–2050 Ma). Magmas for this time period are dominantly dacitic and also display geochemical characteristics of arc magmatism, but also contain high-K, indicative of melting in a thickened volcanic arc.
AB - This study reconstructs the evolution of one of the oldest Paleoproterozoic arcs, which formed shortly after a period of momentous change when the Earth transitioned out of the Archean. We present new stratigraphic, geochemical and geochronological data of the Toumodi Greenstone Belt (Ivory Coast, West Africa) integrated with local and regional data to better constrain its construction and evolution. The belt consists of four main stratigraphic events: [1] A ca. 2345 Ma tholeiitic sequence formed on the sea floor far from any landmass. This juvenile crust is the oldest Birimian supracrustal sequence known and represents either a dismembered oceanic plateau or ridge basalt; [2] Nascent arc formation (ca. 2220–2160 Ma) developed initially in a subaqueous environment and transitions into emergent volcanic centres. Near Toumodi, most deposits consist of volcaniclastic debris emplaced in subaerial to shallow-water environments, but also include minor pyroclastic vent-proximal deposits. Magmas for this event are mainly basaltic andesite to andesite and are enriched in LILE and have negative Nb, Ta and Ti signatures, all of which are consistent with water-fluxed melting typical of arc magmatism. Inherited zircons and mafic xenocrysts/xenoliths together reflect the older history and nature of underlying mid- to lower-crustal rocks, [3] An intra-arc rifting-event marked by a unconformity between events 2 and 4 the correlation with pillowed tholeiitic basalts; and [4] Construction of a mature arc (ca. 2150–2100 Ma) that consists of emergent dacitic volcanic centres and more distal volcaniclastic sediments, and overlain by post-magmatic sedimentation and red-bed formation (ca. 2100–2050 Ma). Magmas for this time period are dominantly dacitic and also display geochemical characteristics of arc magmatism, but also contain high-K, indicative of melting in a thickened volcanic arc.
KW - Geochronology
KW - Ivory Coast Greenstone
KW - Paleoproterozoic
KW - Volcanic Arc
KW - West African Craton
UR - http://www.scopus.com/inward/record.url?scp=85151450465&partnerID=8YFLogxK
U2 - 10.1016/j.precamres.2023.107029
DO - 10.1016/j.precamres.2023.107029
M3 - Article
AN - SCOPUS:85151450465
SN - 0301-9268
VL - 389
JO - Precambrian Research
JF - Precambrian Research
M1 - 107029
ER -