Carbonatitic Volcanic Genesis of Hetaoqing Fe‐Cu Deposit in Central Yunnan, China

Abstract

. The Kunyang rift on western margin of Yangtze Platform is a continental rift, and also a rare Precambrian Fe‐Cu mineralization zone in China. The Wuding‐Lufeng mineralization area in the middle section of the rift is an important part of the zone, and an elliptic‐shaped volcanic collapsed basin, controlled by a ring fracture system with carbonatitic volcanic rocks mainly occurring along the northwestern edge of the basin. The Hetaoqing Fe‐Cu ore deposit at the western side of the basin is hosted in carbonatitic volcanic rocks and pyroclastic sedimentary rocks. The original ore bodies occur as layers, bands and lenses conformable to the host carbonatitic rocks. The ores usually appear as massive, impregnated and granular in carbonatitic rocks, and as brecciform and sandy in pyroclastic sedimentary rocks. Ore‐forming minerals are magnetite, hematite, chalcopy‐rite, bornite, pyrite, carrollite, molybdenite, cobaltite and skinnerite, and secondary minerals limonite, chalcocite, azurite, malachite and tenorite. Gangue minerals are calcite, dolomite, ankerite, common hornblende, arfvedsonite, augite, aegirine‐augite, albite, phlogopite, biotite, chlorite and apatite. Evidences of mineral chemistry, trace elements and isotopic ratios of ores, as well as geological features, suggest that the original ores are igneous in origin. Chemical features of magnetites in the deposit belong to carbonatite type, and are similar to those from the Bayan Obo carbonatites. The ores are rich in iron, titanium, rare earth elements, niobium, tantalum, gold, silver, phosphor and sulfur. These features indicate that the Fe‐Cu deposit associated with volcanic activity in the Wuding‐Lufeng basin is alkali‐carbonatite volcanic type.

Geochemical constraints on the genesis of the Bayan Obo Fe–Nb–REE deposit in Inner Mongolia, China

“…Most ages are Sm-Nd isochron ages published in the Chinese literature, with a clear peak at 1.2-1.6 Ga (Anon, 1988;Philpotts et al, 1991;Wang et al, 1994;Zhang et al, 1994Zhang et al, , 2003Fan et al, 2002;Liu et al, 2005). A zircon U-Pb age of 1925 ± 8 Ma, measured on a Bayan Obo carbonatite dyke was once taken as the age of carbonatite magmatism .…”

Carbonatites in China: A review

“…The main ore minerals are magnetite and hematite with quartz, apatite, bastnäsite-(Ce), monazite-(Ce), allanite, pyrite, chalcopyrite, cobaltite, chalcocite, molybdenite and fluorite also occurring. Values of d 13 C for the carbonatites are K3.0 to C0.9‰ (PDB) and d 18 O 6.0-18.8‰ (SMOW) (Zhang et al, 2003b).…”