Geology and diamond provenance of the Proterozoic Banganapalle conglomerates, Kurnool Group, India

The Banganapalle Quartzite Formation occurs in the Cuddapah Basin in India and is characterized by a basal diamond-bearing
conglomerate horizon. The diamonds within this placer are generally thought to have been sourced from the erosion of kimberlites
of the Wajrakurur cluster. De Beers' India's exploration efforts have resulted in the discovery of a number of dykes within
the basin, with petrographical and geochemical similarities to lamproites. It is proposed that far-field stresses related
to the Eastern Ghats Mobile Belt (EGMB) provided extensional sites during the time of lamproite emplacement. The dykes have
not been dated. However, zircons recovered from heavy mineral stream samples in the area exhibit a number of age groupings,
including one in the range of 1287–1370 Ma. This age is interpreted as the emplacement age of the dykes in this region. Kimberlitic
indicator minerals (KIMs), recovered from conglomerate waste dumps, indicate the uniqueness of the garnet population relative
to that of the known kimberlite clusters to the west of the basin. We propose that the emplacement of lamproites occurred
as dyke–sill complexes at 1.4–1.3 Ga and that the lamproites represent the source of the diamonds in the Banganapalle conglomerates.

班加纳帕勒石英岩层位于印度的库达帕盆地，其特征为底部富含钻石的砾岩层。该砾岩层中的钻石普遍认为源自瓦杰拉库鲁尔集群的金伯利岩侵蚀。戴比尔斯印度公司的勘探努力在盆地内发现了多个岩墙，其岩相学和地球化学特征与辉长岩相似。有观点认为，与东高止活动带（EGMB）相关的远场应力在辉长岩沉积时期提供了扩展的地质环境。这些岩墙尚未进行年代测定。然而，从该区域的重矿物流样品中回收的锆石显示出多个年龄组，其中包括1287-1370 Ma的年龄范围。这一年龄被解释为该地区岩墙的沉积年龄。从砾岩废料堆中回收的金伯利岩指示矿物（KIMs）表明，相对于盆地西侧已知金伯利岩集群的石榴石种群而言，其具有独特性。我们提出，辉长岩的沉积是在1.4-1.3 Ga的岩墙-岩床复合体中发生的，并且辉长岩代表了班加纳帕勒砾岩层中钻石的来源。