Investigation of effective factors in mineralization at Dalli porphyry Cu-Au deposit, Markazi province: base on geological, mineralogical and geochemical evidences

The Dalli porphyry Cu-Au deposit is located in Delijan city, Markazi province, Iran. The deposit, structurally, is placed in the central part of the Urumieh-Dokhtar magmatic arc (UDMA) and consists of two parts, the South Part and the North Part with andesite to andesite basalt wall-rock intruded by granitoids (diorite, quartz diorite and monzodiorite). The aim of this study is the investigation of geologic, mineralogic and geochemical characteristics of the Dalli deposit in order to understand the mineralization factors effective in productive parts. For this purposes, in addition to field observations as well as mineralogical investigations, sampling was done from unaltered, mineralized and less-altered portions for geochemical studies using LA-ICP-MS. Mineralogical and geological evidences indicate that the presence of phyllic, argillic and supergene alterations with more abundance of hornblende, biotite and magnetite in the South Part are effective parameters in increasing the mineralization potential of the Southern Part. As the presence of hornblende, magnetite and lesser abundance of plagioclase indicate high ƒH2O and ƒO2 during magma evolutions and the phyllic and supergene alterations provide conditions for copper precipitation by creating heat loss and copper solution, respectively. This is also supported by high Eu/Eu*, [Dy/Yb]n, [La/Sm]n values and REEs trend with a upward concavity for the South Part.