A geochronological investigation of the Precambrian rocks of Rajasthan, India, was undertaken to decipher the Precambrian geology of Rajasthan in general and the ages of the three episodes of granitization and metamorphism observed in Precambrian rocks in particular. / Discordant zircon ages from granites of the Precambrian rocks of Rajasthan suggest three periods of granitization. The ages of these three periods of granitization in ascending order are, 2600 m. y., 1700 m. y. and 800 m. y. Only 2600 m. y. old granites suggest an episodic lead loss at 710 m.y., probably due to a regional thermal event. The 1700 m. y. and 800 m. y. old granites give a lower intercept age of approximately 70 m. y. / The 2600 m. y. old tectonic event which seems to be confined to the central Aravalli range in Rajasthan, probably the core of the Aravalli mountain, and dates the Aravalli regional tectonic event. / The 1700 m. y. old regional tectonic event is recognized on a much wider area and dates the Delhi regional tectonic event. The granites of this period are either co-folded with the Delhi system of rocks or are post-Aravalli. / The latest regional tectonic event in the Precambrian of Rajasthan is the 800 m. y. old "Erinpura" type event and it is post-Delhi and are represented by massive granitization especially in the southwestern part of Rajasthan (Mt. Abu). / It appears that Malani rhyolites might have inherited some zircons from older rocks and a discordant zircon age of 863 m. y. obtained for these rhyolites is a maximum age for the Malani rhyolites. / Zircons from three different granitic plutons plot on a discordia chord with a crystallization age of approximately 1680 m. y. and a lower intercept age of approximately 70 m. y. It also appears that the 800 m. y. old granitic plutons of "Erinpura" type also give a lower intercept age of approximately 70 m. y. Zircons from these plutons do not fit a 1680 m. y. or any other diffusion curve, suggesting that these zircons represent a mixture of a concordant phase and a discordant phase. In the absence of independent geological evidence, the 70 m. y. old lower intercept age probably represents the age of uplift for the granitic plutons in the Precambrian rocks of Rajasthan. / Source: Dissertation Abstracts International, Volume: 44-07, Section: B, page: 2091. / Thesis (Ph.D.)--The Florida State University, 1983.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_75158 |
| Contributors | SIVARAMAN, T. V., Florida State University |
| Source Sets | Florida State University |
| Detected Language | English |
| Type | Text |
| Format | 148 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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