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Laoniugou, Banshigou |
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Jilin, China |
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Fe
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Super Porphyry Cu and Au
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The Laoniugou and Banshigou iron deposits are located in southern Jilin Province, north-eastern China. Banshigou is just to the north-east of the city of Hunjian, while Laoniugou is a further 75 km to the ENE.
Both deposits fall within the larger, composite 1000 km long by 100 km wide Archaean Liaoji Metallogenic Belt which is elongated in a NE-SW direction and extends from eastern Liaoning Province to northeastern Jilin Province (including the major deposits of the Anshan - Benxi district in Liaoning Province). The country rocks within the metallogenic belt include marine volcaniclastic and sedimentary rocks and greenstone belts in the Eastern Block 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 (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 Liaoji metallogenic belt contains numerous banded iron formations (BIFs) in the Archaean Anshan, Qingyuan, and Longgang Groups in the Anshan-Benxi area of Liaoning Province. The rocks of these groups have been metamorphosed to amphibolite facies from protoliths of mafic, intermediate and siliceous volcanic and clastic sedimentary rocks that were deposited in small volcanic and sedimentary basins along an ancient continental margin (Rodionov, et al., 2004).
The Laoniugou deposit (#Location: 42° 52' 45"N, 127° 27' 40"E) is hosted by banded iron formations in the upper members of the Sandaogou Formation which belongs to the Archaean Anshan Group. The deposit comprises 200 lenticular banded iron formation (BIF) bodies that are concordant with the host sequence and are clustered into 12 'sectors'.
The metallic minerals of the BIFs comprises predominantly magnetite, with minor ilmenite, pyrite, pyrrhotite, chalcopyrite, Ti-magnetite, rutile, sphalerite and galena and traces of hematite and limonite, in a gangue of quartz, cummingtonite, tremolite, actinolite, hornblende, biotite, almandine, hypersthene, chlorite, epidote, calcite, apatite, titanite and zircon. The mineral textures are granular and fibrous-crystalloblastic, with mainly gneissic, massive or banded structures, although locally the ore may be schistose or disseminated. Weak alteration of host silicates includes biotite, actinolite and epidote alteration of pyroxene and amphibole, chlorite alteration of biotite, and sericite alteration of feldspars. Mineral asemblages are: i). magnetite-quartzite; ii). magnetite-hornblende; iii). magnetite-carbonate; iv). magnetite-garnet; and v). magnetite-chlorite.
The Banshigou deposit (#Location: 42° 02' 40"N, 126° 32' 10"E) comprises a series of lenticular BIF bodies distributed over an east-west elongated 8x3 km area which has been divided into three 'sectors'. The host BIFs are amphibolite rich and are in the Lower Banmiaozhi Formation , which belongs to the Lower section of the Archaean Anshan Group.
The orebodies are lensoid, banded and irregular in shape, but are stratigraphically controlled and concordant with the enclosing suite of biotite gneiss, biotite-amphibole schist, amphibolite, biotite-plagioclase gneiss and mica schist. The ore is composed of magnetite with minor pyrite and chalcopyrite, in a gangue of quartz, amphibole and minor garnet. It has banded, streaky and laminated structures (although the high grade ore is generally massive) and mainly a fine crystalloblastic granular texture.
Published ore reserves are (from USGS Open File 03-220):
Laoniugou - 173 Mt @ 30.5 to 35.12% Fe, 44.11 to 47.57% SiO2, 0.19% Ti, 0.06% Mn, 0.07 to 0.105% S, 0.05 to 0.057% P.
Banshigou - 128 Mt @ 45.05 to 45.38% Fe, 0.05 to 1.11% S, 0.055 to 0.073% P.
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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