Asset Details
Do you wish to reserve the book?
Provenance of passive-margin sand (Southern Africa)
Hey, we have placed the reservation for you!
By the way, why not check out events that you can attend while you pick your title.
Oops! Something went wrong.
Looks like we were not able to place the reservation. Kindly try again later.
Are you sure you want to remove the book from the shelf?
Provenance of passive-margin sand (Southern Africa)
Do you wish to request the book?
Provenance of passive-margin sand (Southern Africa)
Please be aware that the book you have requested cannot be checked out. If you would like to checkout this book, you can reserve another copy
We have requested the book for you!
Your request is successful and it will be processed during the Library working hours. Please check the status of your request in My Requests.
Oops! Something went wrong.
Looks like we were not able to place your request. Kindly try again later.
Journal Article
Provenance of passive-margin sand (Southern Africa)
2014
Overview
This study investigates the petrographic, mineralogical, geochronological, and geochemical signatures of river sands across southern Africa. We single out the several factors that control sand generation, including weathering and recycling, and monitor the compositional changes caused by chemical and physical processes during fluvial transport from cratonic sources to passive-margin sinks. Passive-margin sands have two first-cycle sources. Quartz and feldspars with amphibole, epidote, garnet, staurolite, and kyanite are derived from crystalline basements exposed at the core of ancient orogens and cratonic blocks (dissected continental block provenance). Volcanic rock fragments, plagioclase, and clinopyroxene are derived from flood basalts erupted during the initial phases of rifting (volcanic rift provenance). First-cycle detritus mixes invariably with quartzose detritus recycled from ancient sedimentary successions (undissected continental block provenance) or recent siliciclastic deposits (e.g., Kalahari dune sands; recycled clastic provenance). U-Pb ages of detrital zircons mirror the orogenic events that affected southern Africa since the Archean. Damara (0.5-0.6 Ga) and Namaqua (1 Ga) age peaks are prominent throughout Namibia, from the Orange mouth to the Namib and Skeleton Coast Ergs, and also characterize Kalahari dunes and sands of the Congo, Okavango, and Zambezi Rivers. Instead, sharp old peaks at 2.1 Ga and 2.6 Ga characterize Limpopo and Olifants sands, matching the age of the Bushveld intrusion and the final assembly of the Zimbabwe and Kaapvaal Cratons, respectively; discordant ages indicate Pb loss during the Pan-African event. Chemical indices confirm that weathering is minor throughout the tropical belt from South Africa and Zimbabwe to Namibia and coastal Angola but major for quartzose sands of the Congo, Okavango, and upper Zambezi Rivers, largely produced in humid subequatorial regions. Recycling of quartzose sediments is extensive in all of these catchments. From Congo to Mozambique, along the >5000-km Atlantic and Indian Ocean rifted margins, polycyclic detritus reaches commonly 50% and locally up to 100%, in line with the estimated incidence of recycling worldwide. Quantitative information provided by provenance studies of modern sands helps us to better understand the relationships between sediment composition and plate-tectonic setting and to upgrade the overly simplified and often misleading current provenance models. This is a necessary step if we want to decipher the stratigraphic record of ancient passive margins and reconstruct their paleotectonic and paleoclimatic history with greater accuracy.
