 |
| Titel |
The 40Ar/39Ar age record and geodynamic significance of Indo-Madagascar and Deccan flood basalt volcanism in the Sarnu-Dandali alkaline complex, Rajasthan, northwestern India |
| VerfasserIn |
Anjali Vijayan, Kanchan Pande, Hetu Sheth, Kamal Kant Sharma |
| Konferenz |
EGU General Assembly 2017
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250137589
|
| Publikation (Nr.) |
 EGU/EGU2017-351.pdf |
|
|
|
|
|
| Zusammenfassung |
| The Sarnu-Dandali alkaline complex in Rajasthan, northwestern India, is considered to
represent early, pre-tholeiite magmatism in the Deccan Traps continental flood basalt (CFB)
province, based on a single 40Ar/39Ar age of 68.57 Ma. Rhyolites found in the
complex are considered to be 750 Ma Malani basement. Our new 40Ar/39Ar ages of
88.9-86.8 Ma (for syenites, nephelinite, phonolite and rhyolite) and 66.3 ± 0.4 Ma (2σ,
melanephelinite) provide clear evidence that whereas the Sarnu-Dandali complex has
Deccan-age components, it is dominantly an older (by ∼20 million years) alkaline
complex, with rhyolites included. Sarnu-Dandali is thus an alkaline igneous center
active at least twice in the Late Cretaceous, and also much before as suggested by
a basalt flow underlying the Early Cretaceous Sarnu Sandstone. The 89-86 Ma
40Ar/39Ar ages fully overlap with those for the Indo-Madagascar CFB province formed
during continental break-up between India (plus Seychelles) and Madagascar. Recent
40Ar/39Ar work has shown polychronous emplacement (over ≥ 45 million years) of
the Mundwara alkaline complex in Rajasthan, 100 km from Sarnu-Dandali, and
84-80 Ma ages obtained from Mundwara also arguably represent late stages of the
Indo-Madagascar CFB volcanism. Remnants of the Indo-Madagascar CFB province
are known from several localities in southern India but hitherto unknown from
northwestern India 2000 km away. Additional equivalents buried under the vast Deccan
Traps are highly likely. We relate the Sarnu-Dandali and Mundwara complexes to
decompression melting of ancient, subduction-fluxed, enriched mantle lithosphere due to
periodic lithospheric extension during much of the Cretaceous, and hundreds of
kilometers inland from the India-Madagascar and India-Seychelles rifted margins. |
|
|
|
|
|
|