|
Anshan-Benxi District - Gongchangling, Xianshan, Yanqianshan, Qidashan, Yingtaoyuan, Waitoushan, Nanfen, Dagushan |
|
|
Liaoning, China |
| Main commodities:
Fe
|
|
 |
|
|
 |
Super Porphyry Cu and Au
|
IOCG Deposits - 70 papers
|
All papers now Open Access.
Available as Full Text for direct download or on request. |
|
|
The Gongchangling, Yanqianshan, Qidashan, Yingtaoyuan, Waitoushan, Xi'anshan, Nanfen and Dagushan iron deposits define an ENE trending belt over an interval of near 100 km in the vicinity of the cities of Anshan and Benxi in Liaoning Province, north-eastern China.
These 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. 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 largest of these is the ~2.54 to 2.51 Ga Dataigou Iron Formation, which in the Anshan-Benxi area has a proven reserve of >5.0 Gt of Fe and an average grade of 35%, the most extensive BIF in China (Wang et al., 2016b). The rocks of the host groups to these iron formations 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).
Iron deposits within the Anshan and Benxi District are hosted within the ~2.56 to 2.51 Ga Anshan Group (e.g., Song et al., 1996; Wan et al., 2012, 2015; Dai et al., 2013; Zhu et al., 2015; Wang et al., 2017; Tong et al., 2019), a metavolcanic-sedimentary sequence that has been divided into two units based on their ages, rock assemblages and metamorphic grade, namely: i). the lower Benxi unit, that was metamorphosed to upper amphibolite facies and mostly comprises ~2563 to 2530 Ma BIFs such as Gongchangling, Waitoushan, Nanfen and Dagushan, and contains mafic to felsic volcanic rocks with lesser volcaniclastic and siliciclastic sedimentary rocks (Zhou, 1994; Wang et al., 2017); and ii). the upper Anshan unit, which is characterised by an upper greenschist to lower amphibolite facies metamorphic assemblage and is dominated by ~2530 Ma BIFs such as Xi'anshan, Dong'anshan and Qidashan, siliciclastic metasedimentary and minor metavolcanic rocks (Zhou, 1994).
The Xi'anshan deposit has been exploited since 1958 and has proved ore reserves of 1.70 Gt, equivalent to 0.68 Gt @ 34.22% Fe (Li et al., 2015). The deposit is hosted by the Neoarchaean Anshan Group, and is unconformably overlain by Sinian (Neoproterozoic) qufrtzite and Quaternary cover. The immediate host rocks are chlorite-, sericite- and carbon-rich phyllite, mica-rich granulite, sericite-quartz schist and banded iron formations (BIFs) of the Yingtaoyuan Formation of the Anshan Group. The Anshan Group is typically migmatised. The Yingtaoyuan Formation at Xi'anshan exhibits a low metamorphic grade, considered to represent a retrograde overprint (Zhai et al., 1990). Ores comprises martite quartzite and magnetite-quartzite, with lesser magnetite chlorite schist, and iron-bearing chlorite phyllite at depth. The deposit occurs as a homocline that forms the western section of the southern limb of the Anshan Synclinorium.
Two fault episodes are recognised. The first is pre-Sinian and strike parallel to the Anshan Group stratigraphy, and includes reverse faults dipping N or NE at an angle of 64 to 74°, accompanied by normal faults dipping at ~ 25°NE. The second comprises an oblique fault set, which also cut the Sinian strata.
A migmatised granite batholith and migmatised metamorphic rocks occur along the southern side of the deposit. No dykes have been recognised within the deposit, other than some metamorphosed lamprophyres.
The orebody is 2600 m long, persists to depths of >1000 m, and has an average thickness of 230 m. It widens from shallow to deep. The eastern section of the deposit strikes nearly east-west, whilst the western part trends almost NW and dips NE. The upper part of the orebody dips at 15 to 25°, whereas at depth this angle has steepened to 40 to 55° and is locally as steep as 60°. Faults locally offset the deposit.
Ore minerals include magnetite, martite and hematite, with lesser magnesian siderite, siderite and ankerite, as well as pyrite veinlets filling fractures in the Fe-bearing minerals. At the surface, secondary limonite is developed which may be schistose, pitted and grooved, and botryoidal. Gangue minerals are quartz, with lesser chlorite, tremolite, actinolite, talc, sericite and calcite, whilst, overall, the ores are fine-grained, granoblastic, banded and low grade. The lower grade ores are composed of martite and quartz, or magnetite and quartz, or tremolite, actinolite, magnetite and quartz, or carbonate, magnetite and quartz, or chlorite, magnetite and quartz. Weathered ores are mainly composed of martite or of limonite, and are distributed on the surface and to depths of 500 m. The transition between weathered and fresh iron formation is characterised by alternating weathered and primary ores. The latter dominate at >600 m. Ore grades ranges from 2 to 42% FeTotal, with an average of 34.22 % FeTotal. Other components include 38 to 66% SiO2, with an average of 47.32%; averages of 0.19% S, 0.04% P and 0.10% Mn. Summarised from Li et al. (2015).
The Gongchangling deposit (#Location: 41° 10' 45"N, 123° 30' 10"E) comprises up to eight BIF units within the metamorphic sequence of the Archaean Anshan Group within an anticlinorium that was intruded and reworked during two periods of granite plutonism at about 2300 to 2100 and 1900 to 1700 Ma respectively. The Anshan Group comprises biotite microgneiss, amphibolite, mica schist, biotite gneiss and garnet-chlorite schist. The metamorphic age of the Anshan Group is 2650 to 2500 Ma, while the protoliths are believed to be older than 2800 Ma (Rodionov, et al., 2004).
There are one to eight BIFs present, and variably developed at Gongchangling. The BIFs individually range from several metres to several tens of metres in thickness, with strike lengths of from several hundred metres to 1 km. Textures within the BIFs are banded, paragneissic and massive. The ore minerals are coarse magnetite, quartz and minor amphibole. Moderate tonnages of high grade ores are known, with >50% Fe are mainly composed of magnetite, maghemitite, graphite, quartz, garnet, cummingtonite, pyrite and pyrrhopyrite with dominantly massive textures and local porous zones. The bulk of the BIF hoiwever has not been enriched (Rodionov, et al., 2004).
The Qidashan deposit (#Location: 41° 08' 20"N, 123° 20' 30"E) consists of layered bodies BIF units concordant with the host chlorite schist, mica schist, phyllite and quartzite of the Anshan Group. The BIFs are distributed over a stratigraphic thickness of up to 100 to 300 m and strike length of 15 km longand are composed of banded martite, magnetite and quartz. Most of the deposit has been oxidised and leached, although only about 1% of the orebody was high grade ore with > 50% Fe.
The Yingtaoyuan deposit (#Location: 41° 08' 40"N, 123° 05' 30"E) consists of concordant, BIF bodies within a sequence of sericite-chlorite schist, microgneiss, quartz phyllite and amphibolite which belong to the Upper Anshan Group and represent sedimentary protoliths metamorphosed to chlorite-amphibolite facies. The orebody occurs within one major unit of BIF development that is 100 to 340 m thick and occurs over a strike length of 10 km. The BIF is principally composed of banded magnetite and quartz with minor amphibole. Some zones of high grade banded martite-magnetite-quartz ore with >60% Fe occurs as irregular bodies, usually developed near fault zones. K-Ar isotopic dating of muscovite has yielded and age of 2428 Ma.
The Waitoushan deposit (#Location: 41° 30' 05"N, 123° 41' 15"E) comprises three separate BIF units, concordantly intercalated within a sequence of mild to intensely metamorphosed volcanic and sedimentary rock of the Archean Anshan Group. The following minerals assemblages are recorded within the BIF orebodies: i). actinolite-magnetite-quartzite - the dominant assemblage, which occurs in layers and masses with a fine crystalloblastic texture; ii). magnetite-actinolite (high grade ore); iii). actinolite-magnetite; iv). magnetite-dolostone; and v). magnetite-talc schist. Actinolite-magnetite-quartzite is the main assemblage and occurs in layers and masses with a fine crystalloblastic texture. Chlorite, cummingtonite, pyrite and biotite alteration is well developed, especially on the two limbs that contain high grade ore, on fold noses and adjacent to fault zones. Enrichment to form high grade zones is interpreted to be related to mesothermal hydrothermal processes.
The Nanfen, deposit (#Location: 41° 13' 40'' N, 124° 00' 00"E) is composed of BIF units hosted by the Dayugou Formation of the Archaean Anshan Group. The BIF units are concordant with the enclosing sequence of amphibolite, quartz chlorite schist and mica-quartz schist. The BIF is composed mainly of magnetite and hematite, with lesser pyrite, specularite, siderite and pseudomorphic hematite in a gangue of quartz, tremolite, minor muscovite, calcite, actinolite, talc and ferrodolomite. Accessary minerals are apatite and zircon. The BIFs are banded, laminated, schistose and massive, with mainly non-equagranular crystalloblastic and fibrous crsytalloblastic textures. The following minerals assemblages are recorded within the BIF orebodies: i). magnetite-quartzite; ii). tremolite-magnetite-quartzite; iii). magnetite-hematite-quartzite; iv). hematite-quartzite; and v). siderite-magnetite-quartzite. The wallrock alteration is limited and consists of chlorite, pyrite and muscovite.
The Dagushan iron deposit lies within the Dagushan BIF which occurs in the upper part of the metavolcanic- sedimentary sequence of the Anshan unit and is considered to be an Algoma-type BIF that was deposited in an active continental margin setting (Zhou, 1994; Tong et al., 2019). The weighted mean U-Pb ages of the youngest detrital zircons from intercalated metagreywacke within the BIF is 2526 ± 2.5 Ma (Tong et al., 2019), whilst the maximum metamorphic
age for the Anshan-Benxi district is 2512 ±21 Ma (Wang et al., 2016. It has therefore been suggested that the Dagushan BIF was deposited
between 2.53 and 2.51 Ga (Tong et al., 2019), consistent with the ages of other BIFs in the Anshan unit (e.g., Cui, 2014; Wang et al., 2017). Three sedimentary facies are distinguished within the Dagushan BIF: i). oxide facies BIF, with magnetite and quartz being the major minerals; ii). silicate facies BIF, with >20 vol.% silicates with magnetite, cummingtonite, stilpnomelane, chlorite and quartz; and iii). carbonate facies BIF, with prominent siderite, magnetite and quartz. The silicate facies, which is mainly to the south, accounts for ~50 vol.% of the BIF, whilst the oxide facies in the middle is ~30 vol.% and the carbonated facies, accounting for ~20 vol.%, is to the north. Two transitional facies mark the gradation between the three major assemblages.
The Dagushan BIF is conformably interbedded with chlorite-quartz schist, biotite gneiss and minor mica-quartz schist and represents a complete transgressive-regressive cycle from fine-grained metashales through BIF with lesser chlorite-quartz schist to a coarsening upward metagreywacke (Tong et al., 2019). This succession is directly overlain by the Palaeoproterozoic Liaohe Group, which consists mainly of marble and sericite-quartz schist (Zhou, 1994; Wan et al., 2015). The BIF is locally deformed into tight folds with limbs dipping at 40 to 70°NE, and is crosscut by quartz and calcite veins, indicating late-stage hydrothermal alteration. Igneous rocks are widespread within the district, predominantly comprising Mesoarchean granite, Cretaceous granite, granite porphyry, diorite porphyry and dolerite dykes. The ~3.0 Ga Dong'anshan granite (Dai et al., 2014) occurs on the footwall of the Neoarchaean supracrustal sequence hosting the BIF.
Published resource figures are as follows (Rundqvist, et al., Vernadsky SGM, Moscow; Rodionov, et al., 2004, USGS Open File Rept. 2002; and USGS Open File 03-220):
Gongchangling: 760 Mt @ 32.82% Fe
Yanqianshan: 339 Mt @ 30.46% Fe
Qidashan: 470 Mt @ 30.0% Fe
Yingtaoyuan: Large, but not recorded
Waitoushan: 292 Mt @ 31.28% to 33.05% Fe, 0 to 0.15% S, <0.1% P
Nanfen: 1290 Mt @ 31.82% Fe, 49.73% SiO2, 0.38% S, 0.06% P
Xi'anshan - see above.
Those of this group of deposits that are exploited, dominantly Gongchangling, have supplied ore to the steelworks of the Anshan Iron & Steel Company.
The most recent source geological information used to prepare this decription was dated: 2021.
Record last updated: 5/5/2022
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.
|
|
|
|
Dai Y.P., Zhu, Y., Zhang, L. and Zhu, M., 2018 - Meso- and Neoarchean Banded Iron Formations and Genesis of High-Grade Magnetite Ores in the Anshan-Benxi Area, North China Craton - A Reply: in Econ. Geol. v.113, pp. 994-996.
|
Dai Y.P., Zhu, Y., Zhang, L. and Zhu, M., 2017 - Meso- and Neoarchean Banded Iron Formations and Genesis of High-Grade Magnetite Ores in the Anshan-Benxi Area, North China Craton: in Econ. Geol. v.112, pp. 1629-1651.
|
Peng, Z., Tong, X. and Wang, C., 2018 - Meso- and Neoarchean Banded Iron Formations and Genesis of High-Grade Magnetite Ores in the Anshan-Benxi Area, North China Craton - A Discussion: in Econ. Geol. v.113, pp. 989-993.
|
Tong, X., Wang, C., Peng, Z., Li, Y., Hao, W., Mand, K., Robbins, J., Zhang, L., Ke, Q., Zhai, M. and Konhauser, K.O., 2021 - Depositional and Environmental Constraints on the Late Neoarchean Dagushan Deposit (Anshan-Benxi Area, North China Craton): An Algoma-Type Banded Iron Formation: in Econ. Geol. v.116, pp. 1575-1597.
|
Wang, C., Peng, Z., Tong, X., Gao, L. and Zhang, L., 2024 - Geochemistry and Sm-Nd-Fe-Si isotope compositions as insights into the deposition of the late Neoarchean Qidashan banded iron formation, North China Craton: in Mineralium Deposita v.59, pp. 969-993.
|
Wang, C., Zhai, M., Robbins, L.J., Peng, Z., Zhang, X. and Zhang, L., 2024 - Late Archean shelf-to-basin iron shuttle contributes to the formation of the world-class Dataigou banded iron formation: in Econ. Geol. v.119, pp. 725-736. doi: 10.5382/econgeo.5047.
|
|
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.
|
Top | Search Again | PGC Home | Terms & Conditions
|
|
