PRESENT STATUS OF THE GEOCHRONOLOGY OF THE PRECAMBRIAN ROCKS OF RAJASTHAN
PRESENT STATUS OF THE GEOCHRONOLOGY OF THE PRECAMBRIAN ROCKS OF RAJASTHAN
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DOI：
10.1016/0040-1951(84)90199-9
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发表时间：
1984-01-01
期刊：
影响因子：
2.9
通讯作者：
SASTRY, CA
中科院分区：
文献类型：
--
作者：
CHOUDHARY, AK;GOPALAN, K;SASTRY, CA
本文总结和讨论了我们和其他人对拉贾斯坦邦前寒武纪岩石的年龄测定，主要是Rb、Sr分析。（1）3000 - 2900百万年的酸性岩浆活动的广泛时期，(2)26 - 25百万年，(3)2000 - 19亿年，(4)17 - 15百万年（5）8.5 - 7.5亿年。被确认了身份该地区最古老的岩石是乌代布尔东部尚未确定日期的带状片麻岩（BGC），由29.5亿年的Untala花岗岩侵入。因此是中太古代的迄今为止，基底状态归因于2600百万年的Berach花岗岩。已经站不住脚了对上覆的Aravalli超群的开始和持续时间的放射性控制尚不令人满意，尽管下限为2000百万年。表示。苍鹭的原始德里岩石记录了两次在空间和时间上相距甚远的岩浆事件。而最早的花岗岩活动在1600百万年。仅在东北部的Alwar盆地有记录，较年轻的活动在8.5 - 7.5亿年之间。Aravalli山脉的“Erinpura型”花岗岩沿着Aravalli山脉和Aravalli山脉西部平原的Malani流纹的年代几乎一致。
Age determinations, mostly by RbSr analyses, of the Precambrian rocks of Rajasthan by us and by others are summarized and discussed. Broad periods of acid magmatism at (1) 3000−2900 m.y., (2) 2600−2500 m.y., (3) 2000−1900 m.y., (4) 1700−1500 m.y. and (5) 850−750 m.y. were identified. The oldest rocks in the area are the yet undated banded gneisses (BGC) east of Udaipur, intruded by the Untala granite dated at 2950 m.y. and hence of mid-Archean age. The basal status hitherto attributed to the Berach granite dated at 2600 m.y. is no longer tenable. The radiometric control on the beginning and duration of the overlying Aravalli Supergroup is not yet satisfactory, though a lower limit at 2000 m.y. is indicated. Heron's original Delhi rocks have recorded two magmatic events widely separate in space and time. While the earliest granitic activity at 1600 m.y. is recorded only in the Alwar basin in the northeast, the younger activity between 850-750 m.y. is widespread, as shown by the nearly concordant ages of “Erinpura-type” granites along the Aravalli mountain Range and the Malani rhyolites in the western plains of the Aravalli Range.