Volcanic and sedimentary rocks of the Sinclair Supergroup occur in the Konkiep
Terrane of Southern Namibia. Three volcanic and sedimentary cycles are recognised.
The Barby Formation belongs to the second cycle which consists of the Kunjas
Formation, Barby Formation and the Guperas Formation. In this work, the volcanic
rocks of the Barby Formation, a key unit in the Sinclair area are described and dated.
The coeval Spes Bona Syenite and the Tiras Granite are also described and dated. The
rock types in the Barby Formation are rhyolites, basaltic trachyandesites, trachybasalts
and trachydacites as well as volcanoclastic rocks. The rocks are largely undeformed
and partly altered by deuteric processes and also mildly metamorphosed. Based on
geochemistry of the rock samples and previous work, the bulk of rock types are calcalkaline
although some alkaline rocks are present. U-Pb dating and Lu-Hf isotopic
microbeam analyses were made on zircon and baddeleyite grains from four samples
using cathodoluminescent images. A Barby rhomb porphyry sample gives an U-Pb
baddeleyite age of 1217 ±2 Ma and a Barby felsic tuff has an 207Pb/206Pb zircon age of
1214 ±5 Ma. The Spes Bona Syenite which intrudes the Barby formation has a U-Pb
baddeleyite age of 1217 ±3 Ma and an indistinguishable Rb-Sr biotite isochron age of
1238 ±20 Ma, showing that there was no regional metamorphic event. Subduction zone
assemblages are generally made of high potassium basalts or calc-alkaline association.
The Barby Formation records such assemblages. The Barby Formation reflects a
subduction event which took place during the assembly of the Rodinia supercontinent.
It is slightly younger at 1204 ±9 Ma and reflects the end of subduction-related
volcanism due to the collision of Namaqua terranes with the Konkiep Terrane. The
Spes Bona syenite and the Barby units have Lu-Hf crustal residence ages between
1682 and 1873 Ma suggesting the two units probably formed from a mixture of
juvenile and older crustal material.
SSA, R (2021). The Geochemistry And Geochronology Of The Barby Formation In The Sinclair Area, Southern Namibia. Afribary.com: Retrieved May 10, 2021, from https://afribary.com/works/the-geochemistry-and-geochronology-of-the-barby-formation-in-the-sinclair-area-southern-namibia
Research, SSA. "The Geochemistry And Geochronology Of The Barby Formation In The Sinclair Area, Southern Namibia" Afribary.com. Afribary.com, 27 Apr. 2021, https://afribary.com/works/the-geochemistry-and-geochronology-of-the-barby-formation-in-the-sinclair-area-southern-namibia . Accessed 10 May. 2021.
Research, SSA. "The Geochemistry And Geochronology Of The Barby Formation In The Sinclair Area, Southern Namibia". Afribary.com, Afribary.com, 27 Apr. 2021. Web. 10 May. 2021. < https://afribary.com/works/the-geochemistry-and-geochronology-of-the-barby-formation-in-the-sinclair-area-southern-namibia >.
Research, SSA. "The Geochemistry And Geochronology Of The Barby Formation In The Sinclair Area, Southern Namibia" Afribary.com (2021). Accessed May 10, 2021. https://afribary.com/works/the-geochemistry-and-geochronology-of-the-barby-formation-in-the-sinclair-area-southern-namibia