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Sanheming |
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Inner Mongolia, China |
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Fe
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Super Porphyry Cu and Au
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The Sanheming iron deposit is located some 100 km north-west of Hohhot in the Yinshan Mountains of central Inner Mongolia, north-eastern China (#Location: 41° 26' 00"N, 110° 57' 00"E).
The deposit lies within the 200x30 km Yinshan Metallogenic Belt, hosted by banded iron formations (BIFs) in the Sanminghe Group of the Paleoproterozoic Changcheng System, part of the overlap assemblage overlying the Archaean Yinshain terrane on the northern margin of the North China craton.
The North China Craton is composed of the two older, north-south elongated, Eastern and Western Archaean Blocks, separated by a Central Orogenic Belt. It has been interpreted that the Eastern and Western Blocks collided at 2.5 Ga during an arc/continent collision, forming a foreland basin over the Eastern Block (the Quinglong foreland basin), a granulite facies belt on the western block, and a wide orogen between the two blocks. This was followed by post-orogenic extension and rifting, simultaneous with the development of a major ocean lapping onto the northern margin of the craton during the early Paleoproterozoic (Kusky and Jianghai, 2003).
A magmatic arc terrane, which is indicated to have developed in this ocean and was elongated east-west parallel to the northern margin of the craton, collided with that northern craton margin by 2.3 Ga, to form a 1400 km long orogen known as the Inner Mongolia-Northern Hebei Orogen. A 1600 km long granulite-facies terrane formed on the southern margin of this orogen, representing a 200 km wide uplifted plateau as a result of crustal thickening. This granulite facies terrane comprises a southern belt of reworked Archaean basement and a northern metamorphosed accretionary belt. To the south of this granulite terrane, the Archaean sequences have mainly been subjected to amphibolite facies matamorphism. The orogen was converted to an Andean-style convergent margin from 2.20 to 1.85 Ga, reflected by belts of plutonic rocks, accreted metasedimentary rocks, and a possible back-arc basin. A pulse of convergent deformation is recorded at 1.9 to 1.85 Ga across the northern margin of the craton (Kusky and Jianghai, 2003).
The Sanheming deposit comprises concordant BIFs within the Paleoproterozoic Sanminghe Group that is divided into the following lithological units from the base upwards: i). lower amphibolite, ii). lower magnetite quartzite, iii). schist, iv). middle amphibolite, v). upper magnetite quartzite, and vi). upper amphibolite. These units are cut by a variety of small dykes and have been metamorphosed to amphibolite and greenschist facies.
Two main BIFs occur at Sanheming, composed mainly of magnetite, hematite and limonite, accompanied by minor pyrite, tremolite and biotite, with textures that are typically idiomorphic-hypidiomorphic, xenomorphic granular and granoblastic. The iron minerals are both banded and disseminated within the silica and silicate gangue.
The mineralisation within the BIFs has been divided into: i). quartz-magnetite, ii). quartz-amphibole-magnetite, iii). amphibole-magnetite, and iv). amphibole-rich magnetite types. The second and third types are the most important.
Reserves of 170 Mt @ 34.82% Fe, 42.78% SiO2, 0.2467% S, 0.0102% P, 0.0058% As have been quoted (Rodionov, et al., 2004, USGS Open File Rept. 2002).
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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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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