Genesis of Manganese Deposits in the Ali Khanzai Block of the Zhob Ophiolite, Pakistan: Inferences from Geochemistry and Mineralogy

• 作者: Andrew C. Kerr Khalid Mahmood Liaqat Ali Muhammad Ayoub Khan Muhammad Ishaq Kakar Rehanul Haq Siddiqui Thomas Ulrich
• 来源期刊: 地球科学学刊（英文版）
• 年，卷（期）: 2020,（5）
• 页码范围: 884-895
• 页数: 12页
• 语种: 英文

摘要

The Zhob ophiolite comprises the Naweoba, Omzha and Ali Khanzai blocks, which are sur-rounded by the sediments of the Alozai Group and Loralai Formation. The Ali Khanzai Block contains met-amorphic, ultramafic, gabbroic, volcanic and volcaniclastic rocks with associated chert. The Zhob manganese deposits found in the Ali Khanzai Block, occur in banded, lenticular and massive forms within red to brown coloured metachert. Braunite and pyrolusite are the main constituent manganese-bearing minerals with mi-nor hausmannite, hematite and barite while quartz is the major gangue mineral with some carbonate miner-als. Geochemical evidence from the major oxides indicates that the manganese mineralization and associated metachert at Zhob were formed by hydrothermal activity with little contribution from contemporaneous volcanic materials and this is confirmed by high Fe/Mn and low Co/Zn ratios and trace element patterns. These deposits formed along with seafloor spreading centres and were later obducted as part of Ali Khanzai Block of Zhob ophiolite.