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Panzhihua |
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Sichuan, China |
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V Fe Ti
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Super Porphyry Cu and Au
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The Panzhihua magnetite, vanadium, titanium deposit is located in Sichuan Province, south-western China (#Location: 26° 37' 10"N, 101° 43' 45"E). It is ~30 km WSW of the similar Hongge deposit.
The deposit occurs within the Panzhihua-Xichang intra-continental rift on the Yangtze Platform, and is hosted by a faulted, layered basic-ultrabasic (gabbroic) complex that is 19 km long and up to 2 km thick, that dips at 50 to 60°NW. It is a member of the extensive 260 Ma Emeishan Large Igneous Province of SW China.
The Panzhihua intrusion is developed parallel to the NNE-SSW regional strike, within the Panzhihua-Xichang rift. Basement, which outcrops to the SE and NW is composed of older Proterozoic metamorphic rocks, overlain by a Neoproterozoic sequence of Sinian quartzites and dolostones, followed by an unconformity and Permian shales, the Permian Emeishan basalts, Permian granite to syenite intrusions that are nearly coeval with the Panzhihua mafic intrusion, and a layer of Triassic siltstones. The SE margin of the intrusion mostly cuts the Sinian sequence, while the NW margin is largely faulted against the Permian Syenite and Triassic siltstones.
Pecher et al. (2013) consider the Panzhihua intrusion to be an irregular, open S-shaped body, essentially comprising a discordant dyke, with near-concordant sill-like segments at either end, expressed at the surface as a flattened 'stair case' shape, as follows:
i). A southern, generally concordant segment (from Nalaqing to Gongshan), where the intrusion is oriented at ~45° although the dip is uncertain due to faulting;
ii). The central discordant. dyke-like segment, where the overall trend of the intrusion is ~15°;
iii). A northern segment (Zujiabaobao pit), where the intrusion is oriented from 60 to 110°.
The intrusion is layered throughout, being characterised by decimetre- to centimetre-scale layers of contrasting mineralogy and grain size. Most of the zones of the complex display variable-scale rhythmic modal layering. This layering within the complex is due to changes in the relative proportions of dark minerals (clinopyroxene, olivine and magnetite) and leucocratic minerals (plagioclase feldspar) and variations in grain size. The dark minerals are predominant in the lower parts of each layer, while lighter minerals dominate the upper parts. The layering is locally cut by the injection of light-coloured veins of leucogabbro, parallel or slightly oblique to the layering. Particularly in the light-coloured bands, a clear preferred orientation of mineral grains is irregularly developed. Locally, this foliation is oblique to the banding but in general it is parallel and there is no evidence that the banding, is also a plane of flattening (Pecher et al., 2013).
Zhou et al. (2005) and Pang et al. (2008) reported that the intrusion is differentiated from highly mafic, often magnetite-rich, melanogabbro at the base, grading through normal gabbro to leucogabbro near the top. It intrudes Neoproterozoic dolostones, marls and quartzites, which, at the contact of the intrusion, have been transformed into marbles and skarns within an up to 300 m wide contact aureole, due to multiple generations of mafic dykes which invaded the carbonate wall rocks during emplacement of the main intrusion. The upper aureole is not observed because the NW margin of the intrusion is cut by a fault and intruded by syenite.
Unlike the northern and southern segments, there is a strong obliquity between the layering and the walls of the intrusion in the central segment. Over the entire intrusion, there is some variation in the orientation of the banding, but overall it strikes ~95° with a dip of 50°N (Pecher et al., 2013).
This is inconsistent with the earlier interpretation that the intrusion is a large sill whose floor was the present-day southeast contact of the intrusion, in which case, the layering should be parallel to the contact.
Pecher et al. (2013) consider that this layering cannot have formed by crystal settling or in-situ growth on the floor of the intrusion, but instead propose it resulted from inward solidification of multiple, individually operating, convection cells, and that ore formation was triggered by interaction of magma with carbonate wall rocks.
The oxide ores are present as layers and lenses within the gabbros and are concentrated in the lower parts of the intrusion. The ore ore textures and associated mineral assemblages have been interpreted to indicate that the ore bodies formed by very late-stage crystallisation of V-rich titanomagnetite from an immiscible oxide liquid in a fluid-rich environment (Mei-Fu Zhou, et al., 2005).
The chemical analyses and petrological descriptions of Zhou et al. (2005) show that the ore bodies contain an average of about 25 wt.% Fe2O3, 6.2 wt.% TiO2 and 1375 ppm V. If the parental magma had a composition like that of the picrites of the Emeishan flood volcanic series - i.e., between 11 and 16 wt.% Fe2O3, 2.4 and 3.9 wt.% TiO2 and 295 and 438 ppm V (Xu et al., 2001), this implies enrichment factors of 2 to 4.
The mineralisation occurs in 9 layers that are individually between 3 and 60 m thick.
Production to date has totalled:
50 Mt @ 31.76% Fe, 16 Mt @ 9% TiO2, 400 Mt @ 0.30% V205.
Reserves are quoted by Rundqvist, et al., Vernadsky SGM, Moscow as:
1084 Mt @ 31.76% Fe, 547 Mt @ 9% TiO2, 18.15 Mt @ 0.30% V205.
Total resource (Pacrim 2015 field trip guide):
1333 Mt @ 43% Fe, 11.7% Ti, 0.3% V .
The most recent source geological information used to prepare this decription was dated: 2013.
Record last updated: 5/3/2015
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
Panzhihua
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Selected References:
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Ganino C, Arndt N T, Zhou M-F, Gaillard F and Chauvel C, 2008 - Interaction of magma with sedimentary wall rock and magnetite ore genesis in the Panzhihua mafic intrusion, SW China: in Mineralium Deposita v.43 pp. 677-694
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Mei-Fu Zhou, Robinson P T, Lesher C M, Keays R R, Cheng-Jiang Zhang and Malpas J, 2005 - Geochemistry, Petrogenesis and Metallogenesis of the Panzhihua Gabbroic Layered Intrusion and Associated Fe–Ti–V Oxide Deposits, Sichuan Province, SW China: in J. of Petrology v46 pp 2253-2280
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Pecher A, Arndt N, Jean A, Bauville A, Ganino C and Athurion C, 2013 - Structure of the Panzhihua intrusion and its Fe-Ti-V deposit, China : in Geoscience Frontiers v.4 pp. 571–581
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Yu, S.-Y.,Song, X.-Y., Ripley, E.M., Li, C., Chen, L.-M., She, Y.-W. and Luan, Y., 2015 - Integrated O-Sr-Nd isotope constraints on the evolution of four important Fe-Ti oxide ore-bearing mafic-ultramafic intrusions in the Emeishan large igneous province, SWChina: in Chemical Geology v.401, pp. 28-42.
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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