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Geochemistry, Petrogenesis and Metallogenesis of the Panzhihua Gabbroic Layered Intrusion and Associated Fe-Ti-V Oxide Deposits, Sichuan Province, SW China |
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| Authors: | ZHOU MEI-FU; ROBINSON PAUL T; LESHER C MICHAEL; KEAYS REID R; ZHANG CHENG-JIANG; MALPAS JOHN |
| Affiliation: | 1 DEPARTMENT OF EARTH SCIENCES, UNIVERSITY OF HONG KONG, POKFULAM ROAD, HONG KONG, PEOPLE'S REPUBLIC OF CHINA 2 MINERAL EXPLORATION RESEARCH CENTRE, DEPARTMENT OF EARTH SCIENCES, LAURENTIAN UNIVERSITY, SUDBURY, ONTARIO, CANADA P3E 2C6 3 VIEPS, SCHOOL OF GEOSCIENCES, MONASH UNIVERSITY, VIC. 3800, AUSTRALIA 4 THIRD DEPARTMENT, CHENGDU UNIVERSITY OF TECHNOLOGY, CHENGDU, PEOPLE'S REPUBLIC OF CHINA |
| Abstract: | The Panzhihua gabbroic layered intrusion is associated withthe 260 Ma Emeishan Large Igneous Province in SW China. Thissill-like body hosts a giant Fe–Ti–V oxide depositwith 1333 million ton ore reserves, which makes China a majorproducer of these metals. The intrusion has a Marginal zoneof fine-grained hornblende-bearing gabbro and olivine gabbro,followed upward by Lower, Middle, and Upper zones. The Lowerand Middle zones consist of layered melanogabbro and gabbrocomposed of cumulate clinopyroxene, plagioclase, and olivine.These zones also contain magnetite layers. The Upper zone consistschiefly of leucogabbro composed of plagioclase and clinopyroxenewith minor olivine. Most rocks in the body show variable-scalerhythmic modal layering in which dark minerals, primarily clinopyroxene,dominate in the lower parts of each layer, and lighter minerals,primarily plagioclase, dominate in the upper parts. The oxideores occur as layers and lenses within the gabbros and are concentratedin the lower parts of the intrusion. Ore textures and associatedmineral assemblages indicate that the ore bodies formed by verylate-stage crystallization of V-rich titanomagnetite from animmiscible oxide liquid in a fluid-rich environment. The rocksof the Panzhihua intrusion become more evolved in chemistryupward and follow a tholeiitic differentiation trend with enrichmentin Fe, Ti, and V. They are enriched in light rare earth elementsrelative to heavy rare earth elements, and exhibit positiveNb, Ta, and Ti anomalies and negative Zr and Hf anomalies. Thesilicate rocks and oxide ores of the Panzhihua intrusion formedfrom highly evolved Fe–Ti–V-rich ferrobasaltic orferropicritic magmas. The textures of the ores and the abundanceof minor hydrous phases indicate that addition of fluids fromupper crustal wall-rocks induced the separation of the immiscibleoxide melts from which the Fe–Ti–V oxide ore bodiesin the lower part of the intrusion crystallized. KEY WORDS: magnetite; Fe–Ti-rich gabbro; layered intrusion; Panzhihua; SW China |
| Keywords: | : magnetite Fe– Ti-rich gabbro layered intrusion Panzhihua SW China |
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