29 1 : 59 other ore2forming materials and formed a number of gold source beds and protores along certain strata ; Early Paleozoic stage : a number of

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1 Feb., 2010 : (2010) MIN ERAL DEPOSITS 29 1 Vol. 29 No. 1 Ξ,,,, (, ) 2,, ( ),, ( ) ( ) ( ),, 3,, 2, 2, ; ; ; ; ; ; : P :A Geological features and genesis of gold deposits hosted by lo w2grade metamorphic rocks in central2western Inner Mongolia N IE FengJ un, J IAN G SiHong, HOU WanRong, L IU YiFei and XIAO Wei ( Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing , China) Abstract The central2western Inner Mongolia area, located in the western section of the northern margin of the North China Craton, is one of the most important gold metallogenic provinces in North China. The gold deposits and prospects hosted by low2grade metamor2 phic rocks are widely distributed in two parallel EW2trending Protrozoic rift belts, i. e., the Bayan Obo belt in the north, and the Chaiertaishan belt in the south. Up till now, twenty2three ore deposits and prospects have been discovered, of which Changshanhao, Zhulazaga and Saiyinwusu are the largest ones. Gold mineralization occurs in Proterozoic carbonaceous sandstone, siltstone, carbona2 ceous phyllite, phyllite, slate and schist in the stratoid layer, stratiform, stockwork and veinlike forms. All these gold deposits are characterized by shallow burial, large2size, simple composition and easy mining. Systematic geological investigations indicate that wall rocks of these deposits and prospects vary from place to place, but most of them show an intimate spatial2temporal relation with the Caledonian ductile2brittle fracture zone and the Hercynian intrusive dyke swarm. Geometry of individual ore bodies is mainly con2 trolled by interstratified fracture zones. All the geological features of the gold deposits hosted by low2grade metamorphic rocks in cen2 tral2western Inner Mongolia are similar to features of the Muruntau gold deposit in Uzbekistan. The relationship between the regional crustal evolution and gold metallogeny can be summarized as follows : Middle Proterozoic stage : tectono2magmatism caused by the intense rifting occurring within the Early Precambrian continent or along its margin resulted in the spatial preparation of gold and Ξ (2007BAB25B02),, 1956,,, cei. gov. cn ;

2 29 1 : 59 other ore2forming materials and formed a number of gold source beds and protores along certain strata ; Early Paleozoic stage : a number of gold prospects were formed by regional metamorphism and its related hydrothermal event caused by regional tectonic move2 ment and magmatic intrusion, with middle2 to large2sized gold deposits of this stage also identified ; Late Paleozoic stage : gold de2 posits with economic significance are considered to have been caused by the re2working of the early formed deep2rooted faults and its related Hercynian mafic to felsic magmatism. The extensional faulting and high alkaline magmatism might have played the key role during the formation of the ore deposits. Geological and geochemical features of the gold deposit hosted by the low2grade metamorphic rocks occurring in central2western Inner Mongolia have aroused much attention among geologists both in China and abroad. An inte2 grated analysis of the geological setting and geological and geochemical features of these deposits and their related intrusive rocks will greatly upgrade the understanding of the ore2forming processes of the gold deposits and prospects hosted by low2grade metamorphic rocks in central2western Inner Mongolia. Meanwhile, the genetic model and mineral exploration criteria of these deposits and prospects can also be used during the comprehensive evaluation of the concealed gold deposits hosted by low2grade metamorphic rocks in central2western Inner Mongolia and its neighboring areas. Key words : geology, gold deposit, low2grade metamorphic rocks, geological feature, spatial2temporal distribution, ore2forming process, central2western Inner Mongolia ( ) ( ), 2 (,2002 ;,1993 ;,1991 ; 2,,1989),,,, ( ), (,2007) 20 50, ( ), 1 5 ( 2,1996), ( ), ( ), ,,,,,,,, 2, 1 2,, ( 1, 2 ), (,1991 ;,1989) 2 2 2, 800 km, km 2, 2, 6 18, ( H 1 2H 3 ) ( H 4 2H 5 ) ( H 6 2H 8 ) (H 9 2H 10 ) ( H 11 2H 13 ) ( H 14 2H 18 ), ( ),,, m, , 900 km, 2,, 4 9, (C 123 ) (C 425 ) (C 628 ) (C 9 ), ( ), ( ),,, m (,1991 ;,1989), ( )

3 (,2008,2002 ) 1 ; 2 ; 3 ; 4 ; 5 ; 6 ; 7 ; 8 ;9 2 2 ; 10 ; 11 ; 12 ( ) ; 13 ( ) Fig. 1 Simplified geological map showing the distribution of important metallic deposits and prospects in central2western Inner Mongolia (modified from Hu et al., 2008 and Huang et al., 2002) 1 Quaternary ; 2 Low2grade metamorphic rocks of Middle Proterozoic Bayan Obo Group ; 3 Low2grade metamorphic rocks of Middle Protero2 zoic Chaiertai Group ; 4 High2grade metamorphic rocks of Archean Wulashan Group ; 5 Paleozoic ophiolite ; 6 Measured deep2rooted fault ; 7 Inferred deep2rooted fault ; 8 Copper, lead and zinc deposit ; 9 Iron2niobium2REE deposit ; 10 Gold deposit and prospect hosted by lowgrade metamorphic rocks ; 11 Gold deposit and prospect related to intrusive rocks ; 12 Township of Sumt ; 13 City or banner (county),, 6 % (,2002),,, (,2008 ;Jiang et al., 2005 ;,2002),,,, 2,, ( ) (,1991 ;,1989),,, 2, ( ) (Jiang et al., 2005 ;Nie et al., 2002 ;,2001a ;2001b), 2, ( ),,,,

4 29 1 : 61 ( 1),,,, 500 km 1997,,, ( ), 15 t, ,, ( 1) (Jiang et al., 2005 ;,2001a ;2001b) (, ), 50 t,, ( , 1 2), 2 2 (,2001a ;2001b) Ο,, 2 ( ), (291 4) Ma, t, (Jiang et al.,2005), 2 3 km, (,,2008 ;,2007 ;,1999),,,,, 2, 50 m, ( 2) ( 3), Table 1 Basic geological features of Changshanhao, Carlin and Muruntau types gold deposits ( ) ( ), ; ;, Au2Ag2Pb2Zn2As2Sb2Bi2Mo Au2As2Hg2Sb2Ti2W2Mo As2Au2W2Bi2Te2Se2Ag,,, ( ) CH 4 NaCl Cline et al., 2005 Drew et al., Ο

62 2010 2 ( Jiang et al., 2005 ) 1 ; 2 ; 3 ( ; ; ) ; 4 ; 5 ; 6 ; 7 ; 8 Fig. 2 Sketch geological map of the Zhulazaga gold deposit (modified from Jiang et al.

2 lithologic section ; 2 Calcareous sandstone and silt2 stone ; 3 Various intrusive dykes ( Granitoid aplite ; Diorite porphyrite ; Camptovogesite) ; 4 Gold2bearing alteration zone ; 5 Ore body ; 6

5 ( Jiang et al., 2005 ) 1 ; 2 ; 3 ( ; ; ) ; 4 ; 5 ; 6 ; 7 ; 8 Fig. 2 Sketch geological map of the Zhulazaga gold deposit (modified from Jiang et al., 2005) Middle Proterozoic Agulugou Formation : 1 Meta2sandstone, siltstone and limestone of No. 2 lithologic section ; 2 Calcareous sandstone and silt2 stone ; 3 Various intrusive dykes ( Granitoid aplite ; Diorite porphyrite ; Camptovogesite) ; 4 Gold2bearing alteration zone ; 5 Ore body ; 6 Fault ; 7 Attitude of strata ; 8 Ore zone and its serial number 3 P018 ( Jiang et al., 2005 ) 1 ; 2 ; 3 ; 4 ; 5 ; 6 ; 7 Fig. 3 No. P018 geological exploration section of the Zhulazaga gold deposit (modified from Jiang et al., 2005) 1 Meta2sandstone and siltstone ; 2 Diorite porphyrite dyke ; 3 Ore body ; 4 Gold2bearing alteration zone ; 5 Unaltered rock ; 6 Inferred geological boundary ; 7 Drill hole and its serial number

6 29 1 : 63,,,, 400 m,, 80 m, 13,,, 570 m,, 180 m, 43 ( 2 3),, m,, 170 m, 500 m, 60 m, 415 m, 220 m, ( 3),,, m, m,, (2 10) 10-6, , , ( ) 34 S, (Jiang et al., 2005), 2,,,,, m, 2, 2, (, 2000 ; 2007 ; Jiang et al., 2005 ;, 2001a ; 2001b) 3. 2,, Ο,,,, Ο, 4 : ;, ;, ; 4, ( 4), ( 5),,, ( ), Ο,,, 2,,,,, 70 89, Ο 2 2, 2,, m, m ( 4), 44, 28, 16 44, E2, 55 % ( ),,, m, m, 303 m, 50 m m ; 5 28 m, 12 m, 3 m 48 m ; m, 148 m, 67 m 241 m,,,, m ( 5),, (015 1) 10-6, ,,, ( ) 10-6, Ο

64 2010 4 (,2005 Ο ) A. ; B. 1 ; 2 6 (2 ; 3 ; 4 ; 5 ; 6 ) ; 7 ; 8 ; 9 ( ) Fig.

7 (,2005 Ο ) A. ; B. 1 ; 2 6 (2 ; 3 ; 4 ; 5 ; 6 ) ; 7 ; 8 ; 9 ( ) Fig. 4 Sketch geological map of the Changshanhao gold deposit (modified from Geological Party of Ningxia Nuclear Industry, 2005 Ο ) A. Eastern ore district ; B. Western ore district. 1 Quaternary ; 2 6 Low2grade metamorphic rocks of Middle Proterozoic Agulugou Formation (2 Meta2siltstone ; 3 Phyllite ; 4 Graywacke ; 5 Conglomerate ; 6 Limestone) ; 7 Mafic and Felsic intrusive dyke ; 8 Measured and inferred fault ; 9 Ore body (or mineralized zone) km, 3 40 Ar/ 39 Ar (249 km 2 2 ( 1) 5) Ma, 2 (Nie et al., 2002),, ( ),, (,2008 ;,,2007 ;Nie et al., 2002), 2, ( 6), ( ), ( ) ( ), Ο

29 1 : 65 5 1000E ( 2005 Ο ) 1 ; 2 ; 3 ; 4 ; 5 ; 6 ; 7 ; 8 ( ) Fig. 5 No.

8 29 1 : E ( 2005 Ο ) 1 ; 2 ; 3 ; 4 ; 5 ; 6 ; 7 ; 8 ( ) Fig. 5 No. 1000E geological exploration section of the eastern ore district in Changshanhao 1 Middle Proterozoic phyllite ; 2 Middle Proterozoic meta2sand2 stone; 3 Lamprophyre ; 4 Diorite porphyrite ; 5 Ore body ; 6 Boundary between oxidized and sulfide ore zones ; 7 Drill hole and its serial number ; 8 Unclassified stratigraphic unit Ma Ma , Ma ( Kempe et al.,2001) 21, 5 ( 6 7) ( 32 ) 2 2, , ( ) Ma ( ) (279 18) Ma (Morelli et al.,2007 ; Kempe et al.,2001),,, 80, 500 m, 350 m ; m, 215 m ;, ( Morelli et al., m, 288 m ( ;Drew et al.,1996), ), m, ( ) 9,2 5,,, m, 150 m ; m, 35 m ; m, 85 m,,,,, 2,, (4 18) 10-6, ,, (2 15) 10-6, , , 40 Ar2 39 Ar (249 5) Ma, 40 Ar2 39 Ar (Nie et al.,2002),, 2,,, 4 ( Kyzulkum), t, ( Morelli et al., 2007 ; Drew et al.,1996) 2, ( ) 20 2, 2 2,, ( Kempe et al.,2001),, ( ) 1,,

66 2010 6 ( 2007 ) 1 ; 2 ; 3 6 2 (3 ; 4 ; 5 ; 6 ) ; 7 ; 8 ; 9 ; 10 ; 11 ; 12 ; 13 ; 14 ( ) Fig. 6 Sketch geological map of the Saiyinwusu gold deposit (modified from Zhang et al.

9 ( 2007 ) 1 ; 2 ; (3 ; 4 ; 5 ; 6 ) ; 7 ; 8 ; 9 ; 10 ; 11 ; 12 ; 13 ; 14 ( ) Fig. 6 Sketch geological map of the Saiyinwusu gold deposit (modified from Zhang et al., 2007) 1 Quaternary ; 2 Sedimentary rocks of Carboniferous Baoligemiao Formation ; 3 6 Low2grade metamorphic rocks of Middle Proterozoic Bayan Obo Group (3 Bilute Formation ; 4 Halahuogete Formation ; 5 Jianshan Formation ; 6 Dulahala Formation) ; 7 Metamorphic rocks of Archean Wulashan Group ; 8 Hercynian granitoid intrusive dyke ; 9 Hercynian diorite dyke ; 10 Kimberlite dyke ; 11 Normal fault ; 12 Thrust fault ; 13 Unconformity ; 14 Gold ore district (zone, dyke) and its serial number 7 (,2007 ) 1 ; 2 ; 3 Fig. 7 Simplified geological exploration section of the Saiyinwusu gold deposit (modified from Zhang et al., 2007) 1 Location of drill hole ; 2 Measured ore body and its serial number ; 3 Inferred ore body

10 29 1 : 67, ( ), 2 ( Groves et al.,1998 ;2007) 2 ( ), 2,,, (,2007 ; Ren et al.,1999 ;,1991) 2,, 2 ( ),, 2,,, : 2, ( ) 2,,,, ;,,, 2, 2, p H E h, (,2005a) 2,,,,, 2 2, km (,2005b), 2,,, ( ), ( ) CO 2 CH 4 N 2 S As Au Sb,, (,2005a), ( ), ;,,, (?) ; (,,1991 ;,1989),, 2, (,2008 ;,2007 ; (,2006 ;,1999), (,2002),,?) ( ), : ( 2 ),, ; (Jiang et al., 2005 ;,2001a ; ;, 2001b),, (,2007 ; Ren et al., 1999 ;,1991 ;,1989),,,, (,,,2002 ;,1991 ;,1989),, 8 5 (1),, 2

11 Fig. 8 Schematic diagram showing the formation processes of the gold deposits and prospects hosted by low2grade metamorphic rocks in central2western Inner Mongolia (2),,, 2,, 2 (3), 2 2,

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km 5 km Pt 2 x 2 1 Au 65 ~ ~ km 5 km 10 km 2 Au Au

km 5 km Pt 2 x 2 1 Au 65 ~ ~ km 5 km 10 km 2 Au Au 38 1 2015 3 JOURNAL OF EAST CHINA INSTITUTE OF TECHNOLOGY Vol. 38 No. 1 Mar. 2015 doi 10. 3969 /j. issn. 1674-3504. 2015. 01. 002 1 2 1 2 3 1. 471000 2. 471000 3. 510640 9 P618. 51 A 1674-3504 2015 01-0012-11.