Strata in the area and its mineralization characteristics

The strata exposed in the study area mainly include Neoarchean, Yuanguyu, Paleozoic, Mesozoic and Cenozoic. Now from the old to the new, as described below.

I. Neoarchean

The oldest stratigraphic unit and basement rock series in the NeoArchean region are mainly exposed intermittently in Taibusiqi and the south of Chifeng City along the uplift of Inner Mongolia, which constitutes a regional east-west basement volcanic-sedimentary formation. The regional stratigraphic names mainly include "Hongqi Ruth Group, Anshan Group and Jianping Group", and the corresponding strata are Wulashan Group in western Wulashan and Daqingshan area. According to "Regional Geology of Inner Mongolia Autonomous Region" (199 1), Taibus Banner area belongs to Hongqiying subgroup, and the stratum should be below Anshan Group or Jianping Group, which is equivalent to the upper part of Neoarchean Jining Group. The northern part of Zhenglan Banner is biotite plagioclase gneiss of Wulashan Group, with occasional outcrops. The southern part of Chifeng City belongs to Anshan Group or Jianping Group. Due to the Mesozoic and Cenozoic sedimentary caprocks and the structural transformation between Cathaysian and Neocathaysian, this stratum is divided into three rhombic blocks with northeast distribution.

The lower part of Hongqi Ruth Group is composed of garnet biotite granulite mixed with feldspar quartzite, graphite granulite, sillimanite garnet granulite and graphite marble.

Wang Shiqi et al. (1994) divided the metamorphic rocks in the south of Chifeng into Jianping metamorphic complex (equivalent to Xiaotazigou Formation of Jianping Group) and Dayingzi Group (equivalent to Dayingzi Formation of Jianping Group).

According to the characteristics of existing rock assemblage, Jianping metamorphic complex can be divided into three types: ① gneiss+amphibolite+granulite+magnetite quartzite assemblage, which is distributed in the southeast of Nuruhushan uplift belt, namely, Zhulike-Jianping-Lingyuan, Hebei Province; ② Oblique amphibolite+gneiss+magnetite quartzite, with occasional granulite, distributed in Beizifu area in the north of Nuruhushan uplift belt and south of Heilihe fault in the south of Maanshan uplift belt; ③ Oblique amphibolite+gneiss+a little marble, with occasional basic granulite, mainly distributed in Honghuagou and other areas in the famous mountain uplift zone.

Metamorphic rocks can be divided into upper crustal rocks and intrusive rocks. The rocks in the upper crust include magnetite quartzite, marble, amphibole and biotite monzogneiss. Intrusive rocks include gabbro, tonalite invaded in different stages, augite and granodiorite (TTG). Among them, TTG rocks account for more than 60% of the exposed area of metamorphic rocks, and the rocks in the upper crust only exist in the form of solitary xenoliths.

The whole rock Sm-Nd age of the metamorphic rock is 2847Ma (supracrustal rock series), and the zircon U-Pb age of the intrusive rock of TTG rock series is 2600～2500ma. Zircon U-Pb age of biotite plagioclase gneiss (tonalite) collected from Honghuagou area of Chifeng is 2575Ma (Cui,1991; Wang Shiqi et al., 1994) represents the emplacement age of TTG rocks in the study area. Taking 29001000 Ma as the dividing age between Archean (middle) and NeoArchean, the exposed basement rocks in the study area belong to NeoArchean (Li Yonggang et al., 2003).

Dayingzi Group is mainly distributed in the central part of Nuruhushan uplift belt and Dayingzi and Jinchanggouliang areas in the north-central part of Maanshan uplift belt. According to rock assemblage, it can be divided into two types: ① gneiss (granite gneiss, amphibole plagioclase gneiss, plagioclase gneiss)+amphibole+crystalline schist (amphibole schist, amphibole plagioclase schist, chlorite schist, actinolite schist, biotite quartz schist)+marble assemblage, distributed in Heili River in the middle of Nuruhushan uplift belt and the south of Maanshan uplift belt. ② Gneiss+amphibolite assemblage, marble is rare, distributed in Louzidian-Dachengzi area in the middle of Maanshan uplift belt.

The protolith formation of this metamorphic rock is equivalent to ultrabasic volcanic rock series, basalt, andesite and Komatite with tholeiite and andesite intermediate-basic volcanic rock series, and intermediate-acid volcanic-sedimentary rock series of rhyolite, andesite, pyroclastic rock and ferrosilite, belonging to the Neoarchean geosyncline volcanic island arc formation in North China block.

Generally speaking, the basement metamorphic rock series in this area constitutes a part of the Neoarchean granite-greenstone belt. The metamorphic degree of Jianping metamorphic complex is high amphibolite facies-granulite facies, which is characterized by quartzite and magnetite amphibole and contains a large number of magnets. The metamorphic degree of Dayingzi Group and Hongqiyingzi Group is low amphibolite facies-greenschist facies.

This set of metamorphic rocks is the most important host rock and one of the most important source rocks for gold deposits in the study area. The main large and medium-sized gold deposits in the area and more than 7 1% of gold reserves are concentrated in this stratum. In addition, some sedimentary metamorphic iron ores are mainly developed in this metamorphic rock series.

Second, Yuangu language.

Yuanguyu involved in this area is scattered in the following two areas: First, the Proterozoic Erdaowa Group and the Mesoproterozoic Huade Group, which are mainly marble with schists, are distributed in the island-like Hongqiying subgroup of Archean Valley; Secondly, Mesoproterozoic, which is exposed in the Heilihe area in the south and the Liao Yan subsidence zone in the southeast, includes the Great Wall Group in the lower part and the Jixian Group in the upper part. Sedimentary formations are mainly carbonate-argillaceous rocks and terrigenous clastic rocks. According to the relationship between horizons, it can be divided into Changzhougou Formation, Chuanlinggou Formation and Dahongyu Formation from bottom to top. The Changzhougou Formation is quartzite with a visible thickness of more than 200 meters. Chuanlinggou Formation is composed of sandstone, slate and quartzite, containing layered magnetite, with a visible thickness of 40m. Dahongyu Formation is composed of dolomite marble, banded marble intercalated with sandstone, quartzite and slate. It belongs to shallow marine sediments with a thickness of more than 426 meters. ..

In addition, in the Ming 'anshan area of Harqin Banner, there is a set of crystalline limestone and banded limestone, with a small amount of sand and slate, and the thickness is above1439 m. There is a set of schist, gneiss and marble series in the south of Zheshanzi Gold Mine. In the geological report of1∶ 200,000 (Harqin Banner), it is divided into Ordovician Mingganshan Group and Lower Paleozoic Ordovician Silurian System respectively. Now it is classified as Mesoproterozoic in the national geological map database1∶ 500,000, and this book adopts the latter division scheme.

According to the data in this area, Yuanguyu is an important source rock series of polymetallic minerals such as lead, zinc, molybdenum and iron in this area and its adjacent areas. The Proterozoic Erdaoao Group in Duolun area in the west is the main sedimentary formation and source rock series of sedimentary metamorphic iron ore and skarn iron ore in this area. Xiaojiayingzi large-scale molybdenum deposit occurs in Mesoproterozoic in the Yan-Liao subsidence zone adjacent to the southeast of the study area.

Third, Paleozoic

The Paleozoic in this area is mainly distributed in the north and east of Chifeng, which is an active volcanic-sedimentary rock series formed along the northern margin of North China block, including typical flysch formation, spilite porphyry formation and siliceous rock formation. This area belongs to the Caledonian fold belt of Wendumiao-Onniute Banner. Including CAMBRIAN, Ordovician-SILURIAN, SILURIAN, Devonian, Carboniferous and Permian, with obvious regional zonation. Among them, from the southeast of Onniute Banner to the west of Aohan Banner, the core and wings of Duolun anticlinorium and Aohan Banner syncline were formed by the outcrops of Ordovician-Silurian in the early Paleozoic respectively. From the eastern part of Aohan Banner to Xiawa, Carboniferous is widely exposed. Permian is widely exposed from east to west. The Paleozoic characteristics in this area are as follows.

(1) Ordovician-Lower Silurian (O-S 1)

This set of strata is exposed sporadically in Banlashan-Baiyinban Goumen area on both sides of Xilamulun River, Banboluogou, Mujiadian and Qigan Temple in the south-southwest of wudan, and on both sides of Shaolang River and Yangchangzi River in Jiefangying. The total thickness of the stratum is 700 ~ 2,865 meters, and the general strike of the stratum is near east-west, and the local strike is northwest. This stratum generally suffers from intermediate regional metamorphism. According to the metamorphic degree and lithologic combination, the system is divided into three parts: the upper part is biotite quartz schist, dolomite quartz schist, eryun plagioclase schist mixed with thin limestone slate; The middle part is amphibole plagioclase gneiss, biotite granite gneiss and sugar marble; The lower part is marble, amphibole gneiss and amphibole gneiss.

There are still different opinions on the division of this set of strata. In the lithostratigraphy of Inner Mongolia Autonomous Region, it is considered that this set of schist and marble should belong to Proterozoic products. In some mineral exploration reports, the strata are still divided into Lower Silurian Shuangjing Formation, Middle Silurian Shuiquangou Formation and Middle-upper Shaibusu Formation. But there is no doubt that this stratum is one of the main surrounding rocks of lead-zinc mine in the study area.

(2) Upper Middle Silurian (S2+3)

This set of strata is mostly related to Ordovician-Lower Silurian, mainly distributed in Jiefangyingzi in the south of Onniute Banner uplift, Chenjiayingzi-Bahrain Bridge in the middle reaches of Xilamulun River and Xiashibei in Naiman Banner in the south of Hure Banner. Lithofacies change greatly in the horizontal direction, but the stratum extension is relatively stable and the distribution is relatively regular. The Middle-Upper Silurian (S2+3) is the main stratum, which is a set of medium-low metamorphic sedimentary rocks and volcanic rocks. The Middle Silurian Shawusu Formation (S2s) is exposed along the Yangchangzi River in the south of Onniute Banner. According to the lithostratigraphic units currently adopted, this formation is a set of shallow-sea carbonate rock series, with the lithology mainly consisting of crystalline limestone, reef limestone and marl, with a small amount of porphyry locally, and the thickness is more than 600 meters. The volcanic rocks of Badangshan Formation (S2bν) and Xibiehe Formation (S-DX) are integrated on the Shawusu Formation. Among them, the volcanic rocks in Badangshan are mainly rhyolite porphyry plywood with a thickness of 1064m, belonging to Middle Silurian; Xibiehe Formation is a rock assemblage composed of shallow-sea sandstone, limestone, slate, metamorphic mudstone and reef, and its age belongs to the product from Late Silurian to Devonian. Silurian strata are continuous deposits, which are in contact with the underlying strata (O-S 1) as a whole. Generally speaking, this set of strata is east-west, but it is northeast-east or northeast-east locally. Together, they form a part of the syncline of anticlinorium and Aohan Banner in Onniute Banner.

(3) Lower Devonian (D 1)

Only the Lower Devonian Gankuntougou Formation is exposed in this area, which is isolated in Gankuntougou area of Aohan Banner. The stratum is composed of shallow marine clastic rocks mixed with limestone, mainly including grayish brown and grayish green clastic rocks (miscellaneous sandstone), slate mixed with limestone and basic volcanic rocks. The stratum can be divided into upper and lower parts. Among them, the upper part consists of complex sandstone, slate and basic volcanic rocks; The middle part is sandy slate, phyllite mixed with sandstone and limestone; The lower part consists of composite sandstone, plywood, calcareous siltstone and fine sandstone. The incomplete thickness is 1438m. The strike of strata is near NW-SE, and the dip angle is generally around 70. It is in fault contact with the overlying Permian Qingfeng Formation.

(4) Carboniferous (C)

It is widely exposed and has complete types, mostly belonging to shallow to marine sedimentary rocks, volcanic sedimentary rocks and volcanic rocks. Discontinuously distributed in Qiaotou, Aohan Banner in the north of Chifeng and Xiashi North Line in Naiman Banner in the east. According to dichotomy, it can be divided into Chaotugou Formation (C 1ch), Baijiadian Formation (C 1b) and Shizuizi Formation (C 1s) from bottom to top. Upper Carboniferous Jiujuzi Formation (C2jj). All groups are integrated.

Lower Carboniferous Chaotugou Formation (C 1ch): distributed in Chaoyanggou, Qifa, Erdaozhang, Mujianggou to Banshaoguo in Aohan Banner. It is a set of rock assemblage dominated by metamorphic volcanic rocks, consisting of metamorphic basic to intermediate acid lava, metamorphic pyroclastic rocks with sericite schist and a small amount of quartzite, with a thickness greater than 22 15m.

Baijiadian Formation (C 1b): refers to a set of marine carbonate rock series distributed in Aohan Banner and located above Chaotugou Formation, overlapping with Shizuizi Formation and showing dog-tooth phase transformation relationship with some sandstone in Shizuizi Formation, so there can be different numbers of sandstone interlayers in different sections. The limestone thickness of Baijiadian Formation in this area changes greatly. The limestone of Baijiadian Formation in Yangjiazhangzi area of Aohan Banner is 2533.3 meters thick, and the thickness extending around it gradually decreases, and the clastic rock interlayer increases. The thickness of Baijiadian is about 500 meters, and the thickness of Fanghougounao area in Naiman Banner changes to 230 meters.

Shizuizi Formation (C 1s): This area refers to the Carboniferous marine sandstone and mudstone (slate) assemblage distributed in Chifeng area, which is distributed in Nanshan, Jiadaogou and Fanghougounao of Baijiadian, Aohan Banner. It is interlaced with the limestone of Baijiadian Formation, and multiple limestone interlayers can appear at the junction.

Jiujuya Formation (C2jj) of Upper Carboniferous: distributed in Jiadaogou, Fanjiazhangzi, Daogelangyingzi, Sanguanyingzi, Tortoise Shell Gully, Xiangyang Institute of Hure Banner, etc. The lithology is a set of continental or marine sandstone (slate) rocks, containing coal, locally intercalated with limestone lens and intermediate acid tuff, with a thickness of135 ~ 664 m.

Generally speaking, this set of strata is dominated by volcanic sedimentary rocks, which gradually decrease or even disappear from bottom to top, with clear sedimentary rhythm; Generally, rocks are subjected to shallow metamorphism, generally slate and phyllite, with schistosity and greenschism locally. Contact metamorphism often occurs in the contact zone of rock mass, resulting in andalusite slate and keratinization.

(5) Permian

Mainly for the lower Permian, a small number of upper Permian, widely distributed. It is a set of extremely thick shallow marine facies or marine-continental sedimentary-volcanic strata, with great changes in lithofacies and slight metamorphism. According to the currently adopted lithostratigraphic division scheme, the Permian in this area mainly includes Sanmianjing Formation, Ertu Formation and Yujiabeigou Formation.

Sanmianjing Formation (Ps) refers to a set of shallow-sea to coastal clastic rocks distributed in Xianghuang Banner to Duolun area in the south of Xilin Gol League, which is unconformity in rock mass or Carboniferous system. The lower part often contains hard limestone and bioclastic limestone, and the upper boundary is in integral contact with the Eritrean Formation or covered by Mesozoic volcanic rocks. The area is mainly distributed in the second branch of Eltu Ranch in Zhengxiangbai Banner in the west, with a total thickness of about 269 meters. The sedimentary time limit of this formation is early Early Permian.

Ertu Formation (Pe): East-west distribution in places such as Xianghuang Banner, Zhengbaiqi Banner, Zhenglan Banner, Duolun County, Hexigten Banner and Onniute Banner. Lithology and thickness change greatly, and the thickness decreases obviously from west to east, with less normal clastic rocks and more volcanic rocks. In Yujiabeigou area of Hexigten Banner, the formation is dominated by andesite mixed with tuff, with granite intrusion at the bottom and contact with Yujiabeigou formation at the top. Nanshan in Wujiagou, Wengniute Banner is a set of intermediate-acid pyroclastic rocks containing andesite. The lower boundary is unclear, and the upper boundary is in contact with Yujiabeigou Formation as a whole. The geological time limit of Ertu Formation is the late Early Permian, and its total thickness is greater than1544.7m.. ..

Yujiabeigou Formation (Py): It now refers to a set of land-sea interactive deposits between Mesozoic volcanic rocks south of Xilamulun River and intermediate-acid volcanic rocks in Ertu Formation, mainly exposed from Zhengxiangbaiqi to Wengniute Banner. The rocks are composed of gray-green and yellow-green tuffaceous sandstone, glutenite, conglomerate, siltstone slice and pyroclastic rock. The upper boundary is unconformity contact with Manketou Aobao Formation, and the lower boundary is integration contact with Ereitu Formation. The sedimentary time limit of Yujiabeigou Formation is from late Early Permian to early Late Permian.

Paleozoic is one of the important source rocks of lead, zinc and copper in this area, especially Ordovician-Silurian and Permian, and large and medium-sized lead-zinc mines such as Xiaoyingzi in this area are all produced in this set of strata. The Paleozoic strata of Zheshanzi gold deposit have also become the direct host rocks of gold deposits. It is also the direct ore-bearing surrounding rock in the area of Beidashan-Fengshui Mountain.

In addition, Paleozoic strata are widely exposed in the southeast neighborhood of the study area (Yanliao subsidence zone), but their sedimentary formation characteristics are different from those in the area. Yanliao subsidence zone is mainly a set of stable caprock deposits, mainly composed of carbonate rocks and clastic rocks.

Fourth, the middle class

At the end of the Late Permian, after the Sino-Korean plate and the Siberian plate merged to form Eurasia, the eastern part of China was influenced by the coastal Pacific tectonic domain since Mesozoic and Cenozoic, forming a series of NE-NNE uplift belts and depression belts, accompanied by strong volcanic activity and magma intrusion. During the intermission of volcanic eruption, clastic rock-argillaceous rock series and coal-bearing clastic rock series dominated by inland lake facies developed. Mesozoic includes Triassic, Jurassic and Cretaceous, among which Cretaceous is the most developed. Among them, for the division of Jurassic and Cretaceous, we refer to the latest international stratigraphic table (2004) and take145.5 4ma as the dividing line between them. Now according to the order from old to new, the Mesozoic in this area is described as follows.

(1) Triassic

It is only found sporadically in the southeast of the research area in western Liaoning, and its lithology is feldspathic sandstone, conglomerate and sandy shale.

(2) Jurassic (J)

The Jurassic is mainly distributed in the western Liaoning area in the southeast of the study area and the Yanliao subsidence zone in the south (northern Hebei-western Liaoning area). Among them, Beipiao Formation of Lower Jurassic is dominated by sedimentary rocks with a small amount of volcanic rocks. The Middle Jurassic is dominated by intermediate-acid volcanic rocks in Lan Qi Formation. Only sporadic Upper Jurassic sediments were found in this area. Tuchengzi Formation of Upper Jurassic-Lower Cretaceous is dominated by purplish red sandstone and conglomerate, and unconformity covers the lower Jurassic.

(3) Jurassic-Cretaceous (J-K)

To sum up, the lithostratigraphic units in this area mainly include Tuchengzi Formation, Manketou Ebo Formation, Manitu Formation, Baiyaolao Formation, Rehe Formation (meaning County Formation, Jiufotang Formation and Fuxin Formation) and Sunjiawan Formation from bottom to top.

Tuchengzi Formation (JKt) refers to purplish red clastic rocks widely distributed in Daxinganling-Yanshan area, with purple, purplish red, grayish green conglomerate, sandstone, siltstone and silty shale in the lower part. The middle part is grayish purple and yellowish brown composite conglomerate mixed with sandstone and clastic composite sandstone; The upper part is grayish green sandstone and tuff, with occasional purple conglomerate. This area is mainly exposed in Chaoyanggou, Niuniu and Carrot Brain in Harqin Banner, and the thickness is between 197 ~ 1503m ... This group is not integrated on Wanbao Formation and Xinmin Formation, but is covered by the unconformity of Manketou Aobao Formation. Its stratigraphic sedimentary age is from the middle and late Late Jurassic to the early Early Cretaceous.

Manketou Aobao Formation (Kmk) refers to acid lava, acid pyroclastic rock, pyroclastic sedimentary rock and neutral volcanic rock which are not integrated on Linxi Formation, Tuchengzi Formation, Wanbao Formation or Xinmin Formation and are covered by Manitu Formation. It is widely exposed in Daxing 'anling-Yanshan area, and the lithology and thickness change greatly in the transverse direction.

Manitu Formation (Kmn) refers to neutral volcanic lava, intermediate-acid pyroclastic rocks, pyroclastic sedimentary rocks and sedimentary rocks mixed with a small amount of acid volcanic rocks, which are integrated above Manketou Obo Formation and below Baiyinlao Formation. Its lower boundary with Manketou Aobao Formation is a large number of andesite, and its upper boundary with Baiyin Laozu Formation is a large number of acidic volcanic rocks. The main features of this area are a set of gray purple, gray and gray green andesite, coarse andesite, dacite, neutral tuff mixed with tuff and tuff. The thickness is generally several hundred meters, and it can reach 1000m or more locally.

Baiyingaolao Formation (Kb): It is a set of variegated acid pyroclastic rocks, acid lava, acid ignimbrite mixed with intermediate acid pyroclastic rocks, pyroclastic sedimentary rocks, sedimentary rocks and andesite. It is integrated on the neutral volcanic rocks of Manitu Formation and covered by the unconformity of the basic volcanic rocks of Meiletu Formation. Thickness varies from 300 meters to 800 meters.

Jehol group (KR) is a set of volcanic rocks, and sedimentary rocks are located above Tuchengzi Formation and below Sunjiawan Formation, including Yixian Formation, Jiufotang Formation and Fuxin Formation.

Yixian Formation (Ky) refers to intermediate-basic volcanic rocks and pyroclastic rocks, mainly developed in Chifeng area, unconformity with upper and middle Jurassic and above strata, with intermediate-acid and alkaline volcanic rocks, pyroclastic rocks and multi-layer sedimentary rocks in some areas, and conglomerate and Jehol fauna fossils at the bottom. Covered by the parallel unconformity of Jiufotang Formation. This area is concentrated in Ningcheng County, Aohan Banner, damiao town-Wengniute Banner Qiaotou Line in Dongshan District, and western Liaoning. Generally speaking, there are two sets of intermediate-basic volcanic rocks (local phase becomes acidic) mixed sedimentary rocks.

Jiufotang Formation (Kjf) is a sedimentary rock combination of gray and green-gray variegated calcareous silty shale, siltstone mixed with marl, sandstone, conglomerate and oil shale, which is not parallel integrated on Yixian Formation, covered by Fuxin Formation and contains Jehol fauna. This area is mainly distributed in Heping Zhuang Basin of Yuanbaoshan, followed by damiao town in Songshan District of Chifeng City and Changsheng Township in the north of Aohan Banner. Covered by Fuxin Formation unconformity, thickness 100~530m ~ 530m.

Fuxin Formation (Kf) refers to a set of coal-bearing strata integrated on Jiufotang Formation, which is mainly composed of gray-white, gray sandstone and conglomerate mixed with dark gray (locally purplish red) mudstone, carbonaceous shale and multi-layer coal seams, covered by unconformity or parallel unconformity of Sunjiawan Formation, and contains animal and plant fossils. Widely exposed in Yuanbaoshan, Pingzhuang basin and other areas. The thickness is110 ~ 900 m.

Sunjiawan Formation (Ksj): It is only exposed in Yuanbaoshan Basin and Pingzhuang Basin in Inner Mongolia. The rock type is mainly a set of red coarse clastic rocks, with purplish red and yellowish brown conglomerate in the lower part, sandstone and coal line in some parts, and yellowish brown sandstone and conglomerate in the upper part, mixed with mudstone and coal seam. Unconformity contact with the underlying Fuxin Formation or Yixian Formation. The total thickness is more than 600 meters

Mesozoic is one of the important source rocks of gold, lead-zinc and molybdenum in this area, but the mineralization scale is generally small, and some of them reach medium scale. At present, the discovered gold deposits are mainly small-scale gold deposits in Nailingou, and molybdenum deposits are lead, zinc and silver deposits in Youfangxi.

V. New World

The strata involved in Cenozoic include Tertiary (Paleogene) and Quaternary.

(1) Tertiary (Paleogene, Neogene, East and North)

The sedimentary characteristics and distribution direction of Paleogene in this area are strictly controlled by geomorphological conditions. According to the lithologic composition, it can be divided into two layers: Hannuoba Formation and Laoliangdi Formation, both of which belong to Miocene. The Xialaoliangdi Formation is only found in the west of Toulang, Chifeng, and is mainly composed of sandstone, shale with conglomerate, mudstone and thin siltstone. The top is a layer of gravel. The thickness is about 25m. The upper boundary is unconformity contact with Hannuoba Formation; The lower limit is unconformity contact with Yixian Formation or older strata. The Upper Hannuoba Formation consists of a set of gray-black, black and purple-gray olivine basalt, pyroxene basalt, dense massive basalt and porous basalt, with red and brick-red mudstone, gray-white mudstone, sandy clay, sandstone and shale, and sometimes contains coal lines. The thickness varies from tens of meters to hundreds of meters. It is widely distributed in Wudan and the west of Chifeng, forming a flat platform along the banks of the river valley, and its occurrence is nearly horizontal. The lower limit is unconformity with Jiufotang Formation of Lower Cretaceous or Fuxin Formation and Baiyinaolao Formation. The Laoliangdi Village in Chifeng is not integrated on the Laoliangdi Formation, and its thickness is only about 24m. The upper boundary of Hannuoba Formation is covered by Quaternary sediments.

(2) Quaternary (Q)

Mainly mud gravel layer, sandy soil, loam, loess and alluvial, lacustrine deposit, distributed along the river valley. Basalt and ice water deposits are locally exposed.

Regionally, there are placer gold and placer platinum in tertiary gravel layer and quaternary gravel layer. According to the regional survey data of1∶ 200,000, the placer gold in the tertiary (Paleogene) gravel layer reached 200 grains /cm3, but the ore-bearing strata were unstable and controlled by the ancient river channel. In addition, the loose quaternary gravel deposits in Qijiagou, Dayaogou and Xiaoweizigou in the south of Harqin Banner all contain placer gold, which was mined locally, but generally on a small scale.