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Marquesado - Alquife, Las Piletas |
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Spain |
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Fe
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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The Marquesado area of the Betic Cordillera of south-eastern Spain contains two iron deposits, Alquife and Las Piletas, which are located approximately 50 km east of Granada. Drilling has indicated the two deposits are continuous below the Quaternary cover that separates the two.
The Betic Cordillera is the westernmost of the Mediterranean Alpine chains and is divided into a metamorphosed internal and an un-metamorphosed external domain. Both deposits are within the Nevado-Filábride Complex comprising a series of stacked thrust sheets of Proterozoic to Palaeozoic basement graphitic metapelite with intercalated quartzite and small bodies of meta-granite and orthogneiss, and an overlying Permo-Triassic cover sequence of meta-pelite, quartzite and marble with subordinate mafic lavas and intrusives as well as local orthogneiss sheets in the upper sections of the pile.
Two main nappe packages are interpretted in the Nevado-Filábride Complex,namely the lower Veleta and upper Mulhacé nappe. The latter, which hosts the mineralisation, includes a basement of graphitic mica-schist and quartzite, overlain by three cover sequences, namely: i). the Tahal Schists of alternating quartzite and mica-schist with garnet, chloritoid and/or amphibolite; ii). a formation of meta-evaporites now consisting of scapolitic marble and meta-pelite, and iii). a marble-calc-schist unit composed of calcitic and dolomitic marble with intercalated calc-schist, mica-schist and quartz-feldspar gneiss.
Both deposits are hosted by the Permo-Triassic marble and calc-schist formation of the Mulhacé nappe, within the calcitic and dolomitic marble facies which are 220 m thick at Alquife and 40 m at Las Piletas. The calcitic marbles are found in the middle and upper two thirds of the formation, while dolomitic marbles dominate in the lower third. Both have a granoblastic or schistose-granoblastic texture and are very pure, with minor muscovite, quartz, rutile with accessory pyrite with traces of chlorite, epidote, albite and tourmaline.
The ore at Las Piletas is stratabound and is predominantly composed of specular hematite with minor magnetite, quartz, muscovite, calcite and dolomite, occuring as a single, massive and homogenous layer of alternating marble and specular hematite laminations. The orebody ranges from several cm, up to 10 to 12 m thick and has well defined contacts with the country rocks.
At Alquife the ore occurs as irregular bodies which have sharp contacts with the wall rocks, and range from a few metres in diameter, to the largest which has dimensions of 350x100x60 m. They are composed of hematite and goethite derived from the supergene alteration of primary sideritic marble which is only preserved in the deeper, un-oxidised sections of the deposit. Textures indicate that the hypogene sideritic mineralisation is a replacement of the original calcitic and dolomitic lithologies which have undergone static metamorphic recrystallisation.
Between 1967 and 1996 approximately 90 Mt of iron oxides were mined from Alquife at an average grade of 54 to 55% Fe. In excess of 60 Mt of ore is estimated to remain on the district.
The most recent source geological information used to prepare this decription was dated: 2006.
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.
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Selected References:
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Torres-Ruiz J 2006 - Geochemical constraints on the genesis of the Marquesado iron ore deposits, Betic Cordillera, Spain: REE, C, O, and Sr isotope data: in Econ. Geol. v101 pp 667-677
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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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