Quartz porphyry of rhyolitic composition though a volumetrically minor is an important component of metavolcanic successions in the Gadag schist belt in the western Dharwar craton. The quartz porphyries are calc-alkaline, enriched in light rare earth elements (La_n/Yb_n ~ 10–20) and with a strong negative Eu anomaly (Eu/Eu*_N=0.45–0.58). These features, coupled with high K₂O/Na₂O (0.8 to 1.46), low Nb/Th (<1), and La_n/Sm_n ratios of 4.2 to 6.0, suggest that rhyolitic magma formed from melt generated by partial melting of basaltic crust, subsequently modified by crustal assimilation and crystal fractionation. The geological setting of the quartz porphyries and the geochemical relationships suggest magmatism at a convergent plate tectonic setting. The zircon U-Pb age of 2588.0 ± 2.4 Ma for the quartz porphyry, together with an age of 2732 Ma for similar volcanic rocks in the Chitradurga schist belt further south, and 2614 Ma for felsic volcanics from the Shimoga schist belt, point to an extended period with episodic arc magmatism in the western Dharwar craton of at least ~144myr.

流变质组成的石英斑岩虽然体积较小，但却是西部Dharwar克拉通Gadag片岩带中超火山演替的重要组成部分。石英斑岩是钙碱性，在轻稀土元素富集的（拉_ñ /镱_Ñ〜10-20）和具有强烈的负Eu异常（EU / EU * _Ñ = 0.45-0.58）。这些特征以及高K ₂ O / Na ₂ O（0.8至1.46），低Nb / Th（<1）和La _n / Sm _n比率为4.2到6.0，表明由玄武岩壳部分熔融产生的熔体形成的流纹岩浆，随后被地壳同化和晶体分馏所修饰。石英斑岩的地质环境和地球化学关系表明，在汇聚的板块构造环境中存在岩浆作用。石英斑岩的锆石U-Pb年龄为2588.0±2.4 Ma，而更南部的Chitradurga片岩带中类似的火山岩的年龄为2732 Ma，而Shimoga片岩带的长石火山的年龄为2614 Ma。达瓦尔克拉通西部至少约144myr的偶发弧岩浆作用延长了一段时期。