N & C Minerals (P) Ltd, Baudha, Kathmandu , Nepal
E-mail: kpkaphle@gmail.com
ABSTRACT
Thoshe
Iron deposit is located at about 200km east of Kathmandu in Thoshe VDC of Ramechhap District, Central Nepal . Small scale mines were in operation
from 1864 onwards till 1952 or so. Existence
of over 1000 of old working pits in the deposit site, few smelting places
around and the remnants of a gun factory at Thoshe Megchan are the solid evidences
of the operations of small scale mines. Local minors used to smelt the iron
ore and the blacksmiths make agricultural tools, utensils, knives, iron chains
etc. The government had established a gun factory based on the refined iron
from Thoshe.
Geological
study of Thoshe iron prospect and preliminary evaluation of the deposit was
carried out by Kaphle and Khan (1995 & 1996) from Department of Mines and
Geology (DMG). Thoshe prospect area is represented by Dorje Khola Formation of
Nawakot Complex. This Formation is divided into Arubote Schist Member and
Dorjekhola Phyllite Member. Arubote Schist member is further divided into (i)
Calc Mica Schist unit which is represented by medium to coarse grained light
gray to gray calc mica schist locally with few siliceous crystalline dolomite/
marble bands and (ii) Chloritic Mica Schist unit which is represented by fine
to medium grained, greenish gray chloritic mica schist occasionally with few
minor basic rock bodies and quartz chlorite veins. 1-3m thick two mineralized
bands/ ore body lie at the upper part of this unit.
N
& C Minerals (P.) Ltd. explored it in four phases. A Regional Geological
map covering the whole lease area, semi detail geological map of the prospect
area (at 1: 10,000 scale) are prepared and traced the ore body by additional
trenching and pitting works. During Second and Third phase, Topographic maps and detail Geological maps
(scale 1:1000 scale) of two separate blocks (Arubote - Sanodadakharka sector
and Singati - Barappu sector) covering just over 100 hectare and geological
cross sections were prepared. The area was extended further south from Jhoreni to Singati and further west from
Singati to Barappu. Chip, channel and bulk samples were collected and analyzed.
On the basis of geology, nature of mineralization, size and shape of the ore
body, it has recalculated the possible Geological reserve as 15.91 million
metric tons with an average grade of 45.3%Fe including all the three blocks.
During 4th phase of exploration a Mining plan, EIA study and Feasibility study
of the deposit is prepared. N&C Minerals Pvt. Ltd. is ready to start mining
activities at the earliest. The Dadakharka - Bhosbhose Sector is under
very thick overburden of rock mass and earth materials. Therefore, first open cat
mining will be started in Singati - Barappu and Arubote - Sanodadakharka
sectors and later start underground mining in Dadakharka - Bhosbhose sector.
Preliminary
beneficiation by simple washing of selected ore samples to remove some unwanted
gangue minerals like chlorite, mica, quartz etc. helped to up grade the low to
medium grade ore (32 - 45%Fe) up to 62%Fe. It is recommended
for metallurgical and industrial testing of the ore
just to confirm that the ore is suitable for making sponge iron which is
demanded by local iron and steel industries.
Thoshe
Iron deposit lies in between Latitude 27o32’30’’ to 27o
35’ 30’’ North and Longitude 86o16’00’’ to 86o18’15’’East
Toposheet no. 2786 06. It is located at Ward No.1 and 2 of Thoshe VDC and Ward
no. 1 of Priti VDC in Ramechhap district in Central Nepal .
The prospect area can be accessed from Jiri via Thoshe Megchan to Singati by 26km
seasonal rough road (Fig.1). Jiri is linked with Kathmandu by Kathmandu
– Jiri road via Khadichaur and Charikot. The nearest airstrip is in
Manthali, the District Headquarter of Ramechhap. A small air strip for Pilates
Aircraft also exists at Jiri. Suitable Helipads are also possible at Chautari
Danda near Arubote and Pokhari near Singati. The iron
deposit is situated about 20 - 26km south east of Jiri (Fig.1) and about 200km
east of Kathmandu . There is a regular
public bus service from Kathmandu to Bhandara
which passes through Singati mine area.
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Fig.1: Location Map of Thoshe
Iron Prospect Area, Ramechhap district (Scale 1: 50,000).
The
highest point of the lease area is 3109m at Tabe
Dada and the lowest point is the junction of Dorje Khola and Khimti Khola (1722m).
The elevation of the deposit area ranges from 2480m to almost 3000m above
msl (Fig.1). Except at some cliff faces Most of the area has low to
moderate slope towards west, southwest and south east and south. The main
drainage of the area is Dorje Khola which joins Khimti River
Previous Works
Jhingran
(1941), Suwal (1956), Manandhar (1965), Weise (1960), Good (1963), Rana (1964
& 1965), Talalov (1972), Kaphle and Khan (1995 & 1996) visited the area
and did some exploration works. Nepal Bureau of Mines (NBM) preliminary
feasibility report (1965), DMG/ ESCAP Geology and Mineral Resources of Nepal
(1993), Mineral Resources of Nepal (2004), and N&C Minerals P. Ltd.'s First
phase Preliminary exploration (2008) and Follow up semi detail and detail
exploration (2009), the old people of Thoshe and Priti villages who were
directly or indirectly involved in mining activities in this area are the main
sources of information.
Fig.2: Northern and Central Parts of Thoshe Iron Deposit (Arubote - Silili - Sanodadakharka - Kopu
Bhalukuna - Kopu - Pahare - Jhoreni -
Kuwakopakha -Bhosbhose Sector (Old working mine sites).
Fig.3: Singati - Ghyangdada - Barappu
sector of Thoshe Iron Deposit (Old working sites)
Preliminary
geological field investigation and assessment of Thosey Iron prospect was
carried out by Kaphle and Khan (1995 & 1996). They prepared a regional geological
map of 100sq km around Thoshe and small part of Khimti Khola area (in 1:63,360
scale), and Semi detail Geological map of Thoshe Iron Prospect area (in
1:16,000 scale) covering about 24sq km and also a detail geological map of 2sq.km
all along the mineralized zone by Compass and Tape survey at 1:2500 scale. Iron
mineralization bands extend at about 4km strike length (roughly north - south
direction) from Arubote to Singati were traced by digging 16 trenches, 2 pits
and locating existing numerous old working pits. 47 chip & channel, 34
grab, 15 bulk samples from the ore body as well as 35 Rock, 102 Stream
sediments and 20 Heavy concentrate samples were
collected
for chemical analysis, petrographic/ mineralogical studies. This field
investigation was successful to trace a 1 - 3m thick (combined) hematite ore
body locally with some magnetite layers/ bands and rarely minor quartz ilmenite
lenses. They reported that the iron content in the ore varies from <30% to
66%.
Fig.4: Geological Map of Thoshe Iron
Prospect area.
N &
C Minerals P. Ltd. after obtaining the prospecting license from DMG has conducted a Preliminary field investigation (Phase -
I exploration) and prepared a Semi-detail Geological map of Thosey Iron
prospect area (12 km2) at 1:10,000 scale (Fig.4) and did some
additional trenching and pitting works to expose the mineralized band and collect
fresh 6 chip, 26 channel, 20 grab and 20 bulk samples of
the ore for chemical analysis, mineralogical study, beneficiation and
metallurgical testing. It was also able to calculate geological ore reserve
roughly 10.5 million ton ore with average grade 42.5% iron. About 3 tons of
bulk and grab samples (ore) were collected from old and new trenches and pits
to perform beneficiation, metallurgical and industrial tests. Some bulk samples
were also prepared by mixing channel and chip samples from the same trench.
BACKGROUND HISTORY AND MINING
ACTIVITIES
From
the literature study it is known that a small scale domestic mining operation
of Thoshe iron deposit was started somewhere in 1921BS (i.e.1864AD), about 145
years before and continued till 2022BS (1966AD).
Smelting of mined ores was continued till 2028BS. Some of the excavated loose
ores are still lying in Bhosbhose Khani area. In those days 15 mines in Thoshe
(e.g. (1) Singati (2) Ghyangdanda (3) Barappu (4) Kawako Pakha (5) Salleni (6)
Bhosbhose (7) Pokhari, (8) Jhoreni (9) Pahare (10) Lapchane, (11) Kopu (12)
Patale (13) Arubote (14) Dangadinger (15) Sotre and other three mines in (16)
Majuwa Khani (17) Soleban Khani in Priti and one in (18) Ghunsa (Dolakha) were
in operation. In early days the annual production of the ore was around 50 tons
and later extended up to 500 tons ore (150 to
200tons sponge iron) per year. Old miners informed that they use to hand crush the
ore to about minus - 40 mesh size fraction and wash them in slow running water
to get the clean concentrate for smelting. It was the process to upgrade the
iron ore. The ore collected from these 18 mines used to smelt in 29 smelting
places in the surrounding areas. Charcoal prepared from local fire woods were
used for smelting. Such smelting procedure took 12 – 14 hours to smelt about
225kg ore into a sponge iron (about 65 - 100kg) depending on the quality of the
ore. The minors use to pay the revenue to the government by the finished iron
itself. The minor use to give the iron to blacksmiths who used to make various
agricultural tools/ instruments like Kodalo, Bancharo, Phali, Khukuri, Ansi,
Tapke, Dadu, Paniyo, Hammer, Chain (Sikri, Fig.5), Nail etc.
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In
those days the people go to Dumja and Haleshi to sell their finished iron
products and get necessary food grains in exchange. The Talukdar of the
government use to collect the revenue from Raitis in the form of Iron Based on
Thoshe Iron deposit the government had also established a small gun factory in
Thosey Megchan in 1921BS. The factory was capable to produce nine barrels of
the gun every day and submit to the military authority. The factory totally closed
in 2007BS. The remnants of the factory are still lying at different parts of
Thosey Megchan (Fig.6). The mining activities were totally closed since 2022 BS
due to government’s new policy, shortage of fuel wood, technical difficulty in
mining at depth and easily availability of finished iron in the free market at
cheap price.
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Old Mining and Smelting Activities
Mining activities were carried out by the local miners
(mainly by Tamang community) since 1864BS only in the easily mineable, rich and
best part of the mineralization from more than 18 mines. More than 1000 such
old working pits apart from exposed ore body can be seen there. At present most
of the pits and few short tunnels are already collapsed and the remaining ones
are also filled with loose debris materials and decay parts of the plants.
Present measurements of some of the pits found to be 5 –18m deep. They have
mined the ore in NE – SW direction along a strip of 30 to 70m wide zone.
Generally the pits are 1.5 to 2 m wide on the surface and much wider at mining
depth. The distance from one pit to another pit is generally 3 to 5m x 5 to 10m
apart. Old miners informed that some of the
pits are interlinked at mining depth to transport ore and manage ventilation in
the pits. They also informed that Gairi Khani at Singati was more than 65ft
deep where three mineralized horizons exist. In this case the total thickness
of the ore body/ bands could reach 4 - 6m (combined). But it has to be
confirmed by test drilling.
The
iron ore collected from different mines used to smelt in smelting places
located in the surrounding regions e.g. at Aahal Dada (Fig.7A) where smelters use to get necessary water from a
pond located near by (Fig 7B). With the help of charcoal as a fuel and red clay
as flux they used to smelt the ore in well managed smelting places. Such
smelting procedure normally took 12 – 14 hours to smelt about 225kg ore into a
sponge iron (about 65 - 100kg) depending on the quality of the ore. From the sponge
iron the blacksmith used to prepare different agricultural tools, dagger, and
utensils. Iron chains, nails etc.
Fig.7A: Old Iron Ore Smelting Place
PRESENT FIELD INVESTIGATION
The
main objective of the present investigation was to do detail Topographical and
Geological mapping, over all assessment of the deposit and compile all the
results of the exploration activities so far completed and present them in this
paper.
All
existing information and data were reviewed and present investigation was planned.
The work was mainly concentrated to explore Thoshe Iron deposit and it was
completed in four different stages of exploration. At the very first stage a topographic
map of 100 hectare (in 1: 1000 scale) was prepared; In Second stage a detail
Geological map of the same 100hectare in the same scale was prepared by
Geological investigation team along with surveyor; and in the third stage
supervision of all the works was done by the Senior Group members along with
their subordinates in December 2009. Overall supervision of the exploration
work was done by the author and Team Leader who is well familiar with Thoshe
Iron deposit. The field supervision included Geological traverse of the lease
area (30km2); field check up of previously prepared Semi-Detail Geological
Map of 12sq km (in 1: 10,000 scale); Trial check
up of detail Topographic map (1:1000 scale) in the field, and also finalize the
detail geological map (1:1000scale) of Arubote
- Silili - Sanodadakharka Block and, Singati - Ghyangdada - Barappu Block. At this time they also did additional trenching/
pitting (240.5m3) and collected 20 channel/ chip samples and 5 grab samples
from the ore body for chemical analysis and beneficiation tests. Detail map
area is shown in Fig. 2 & 3. Dadakharka - Kopu - Pahare - Jhoreni -
Kuwako pakha - Bhosbhose - Singati Block is under very thick overburden of
overlying rocks and it lies in between the other blocks has yet to be mapped in
detail. The team also did rapid assessment of possible mining waste dumping
sites, mined ore storage/ stockpiling sites, possibility of ropeway to
transport ore from the mine to the treatment/ beneficiation site, industrial
site at Hekang Phedi for ore treatment and smelting and storage of sponge iron. They also tried to find the possibility of
generating hydroelectric power from the nearby rivers.
Detail
Geological map (scale 1:1000) was prepared with the help of topographic map and
detail field observations and use of Brunton compass and other field equipments.
Because of thick overburden of residual soil and collapsed earth materials it
was possible to find only outcrops/ exposures to measure their strike, dip and
dip direction in the map area. 3 more Trenches and 5 Pits were dug to expose
the ore body and get fresh ore samples. Additional 10 Channel, 10 chip and 5
bulk samples were collected from the mineralized body mainly from Singati east,
Singati west, Ghyangdanda and Barappu area and one each from Arubote Dil and
Bhosbhose. Samples representing the ore from each pit were analyzed by AAS to verify
the iron content in each sample. All the topographic data and geological information
were digitized and final detail geological map (1:1000scale) was prepared in
electronic format by applying Auto CAD Land Development (compatible with Auto
CAD 2007) and GIS/ Arc info techniques.
GEOLOGY
General Geology
The
regional geological map of this area was prepared by Poudel and Shrestha in
1977 and its adjacent area by Kayastha and Pradhan (1978) and Adhikary (1980). According
to them the area is represented by low to high grade metamorphic rocks which
can be broadly divided into low grade metamorphic rocks of Nawakot Complex and high
grade metamorphic rock of Crystalline Complex separated by Main Central Thrust
(MCT). Lesser Himalayan Gneiss (Ulleri gneiss) occurs towards southern part of
the investigated area. Regional geology of this region is very complex because
of presence of low to very high grade metamorphic rock and a number of
geological structures like thrusts, transverse faults and folds. Kaphle and
Khan (1995 &1996) prepared a regional Geological map of Thosey and part of Khimti
Khola area (100sq km) at 1:63360 scale and compiled various litho-tectonic
units. They also prepared a Semi-detail Geological map of Thoshe area (30sq km)
in 1:16,000scale. For the present work the name of the rock units are taken
from previous works of Kaphle and Khan (1995 & 1996) with further
modification during detail geological mapping (Table-1). N & C Minerals Pvt. Ltd. in its Phase -I mineral exploration
did the geological assessment of the whole lease area (30sq km) and prepared a
Semi-detail Geological map (1:10,000scale) of Thoshe Prospect area (12sq.km).
Geology of Thoshe Iron Prospect
Since
this paper deals mainly with the detail exploration of Thosey Iron deposit,
therefore only the local geology of Thoshe Prospect is described.
Dorje Khola Formation
Dorje
Khola Formation overlies the Thoshe Magchan Quartzite. An anticline structure
is formed and its axis more or less follows Dorje Khola (Fig.4). In the
prospect, rocks of this formation are well exposed on both limbs of the
anticline. The thickness of the formation and lithology slightly varies at
different sections. This Formation is represented by thinly bedded, fine to
medium grained, shining gray calcareous mica schist and crystalline dolomite/
marble towards upper part and gray to dark gray (black) slaty phyllite,
quartzite and green to greenish gray chloritic mica schist and thin layers of
quartzite towards basal part. Locally minor basic rock bodies (amphibolites)
and barren chlorite and quartz veins are recorded. Quartz + Ilmenite and quartz
+ Pyrite + Pyrrhotite lenses and veins are also recorded close to or within the
mineralization bands at Arubote area. At places mica schist is poorly
garnetiferous. Hematite with some magnetite bands occur at the basal part of
calc mica schist and upper part of chloritic mica schist. Isolated crystalline dolomite/
dolomitic limestone blocks and bands are also recorded near Arubote, Patale and
Barappu within this unit.
Foliated
specular hematite is the main ore. The mineralized body which locally also
consists of massive magnetite lenses which is highly magnetic and quite hard,
compact and also comparatively rich in iron content (up to 66% Fe). On the
basis of lithology, grade of metamorphism and mineral content Dorje Khola
Formation is subdivided into two members like (a) Dorje Khola Phyllite Member
and (b) Arubote Schist Member (Table -1).
(A) Dorje Khola Phyllite Member
This
unit is well exposed along Dorje Khola section and forms the core of the
anticline (Fig.4). It consists mainly of gray phyllite and gray to black
carbonaceous slaty phyllite with greenish gray chloritic sericitic phyllite.
Bands of mica schist and quartzite are fairly common.
(B) Arubote Schist Member
This
unit overlies the Dorje Khola Phyllite Member and well exposed on both the
limbs of the anticline. It consists of fine to medium grained greenish gray
chlorite schist and chloritic mica schist, calcareous mica schist with
crystalline dolomite/ marble layers. The
hematite ore body can be traced in 5km strike length (Fig.4) from Arubote to
Singati and further to Barappu.
During
Detail Geological mapping Arubote schist member is further divided into two
Sub-Members/ units (B1) Chloritic mica schist (CLS) and (B2) Calcareous mica
schist (CAS). The hematite mineralization band locally with few magnetite and
rarely ilmenite is located towards the upper part of chloritic mica schist
below the Calcareous mica schist.
Table-1: Lithological Units in Thosey Iron Prospects Area (Kaphle and
Khan 1996 modified by Kaphle, 2010).
Complex/ Group
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Formation/ Member
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Sub Members/ units
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Lithological description
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Nawakot Complex
(?)
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III. Yalung
Formation
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Medium
to coarse grained chloritic garnet mica schist, quartzite, and calcareous
mica schist and silicified marble bands.
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II. Dorje Khola Formation
(B) Arubote Schist Member
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(A) Dorje Khola
Phyllite Member
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(B.2)
Calcareous Mica schist with silicious dolomite bands (CAS)
(B.1)
Chloritic mica schist (CLS)
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Fine
to medium grained chloritic mica schist, calcareous mica schist with crystalline
dolomite/ marble layers and bands. Hematite bands are located below calc mica
schist with crystalline dolomite/ marble. At very few places minor
amphibolite bodies also recorded.
Medium
to coarse grained light gray to gray calc mica schist locally with few
silicious crystalline dolomite/marble bands. (The Hematite mineralization
band lies below this sub member.)
Fine
to medium grained, greenish gray chloritic mica schist occasionally with few
minor basic rock bodies and quartz chlorite veins. The Hematite mineralized
ore body lies at the upper part of the unit below the calcareous mica schist.
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Fine
grained gray to dark gray carbonaceous slaty phyllite, green to greenish gray
chloritic sericitic phyllite, quartzite and chloritic mica schist..
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I. Thosey Magchan Quartzite
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Fine
to medium grained sericitic white to grayish white quartzite. At places
feebly calcareous quartzite bands and silicious dolomite with talc lenses.
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(B.1) Chloritic Mica Schist Sub Member (CLS)
Well
foliated, medium grained, soft, greenish gray to gray chloritic mica schist
occasionally with thin quartzite layers and bands. At places minor basic rock
bodies/ Amphibolite are also recorded within this unit. The Specular (micaceous)
shining silver gray hematite ore body at places with few magnetite lenses and
rarely ilmenite is located at the upper part of this unit.
(B.2) Calcareous Mica Schist Sub Member (CAS)
It comprises of well foliated,
medium grained, light gray to almost white calcareous mica schist occasionally
with few crystalline dolomite/ marble bands layers/ bands (Fig.8). The mineralization
band lies below this unit.
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Regional
geological structures are described by Kaphle and Khan (1995 & 1996). Only
local geological structures are described in this paper. General trend of the
rock is in NW – SE direction and dip 10o - 40o towards
north east or south west. However, at places the trend and the dip direction/ amount
changes locally due to local geological structures like fault and fold and some
other local disturbances. Dorje Khola Anticline is a prominent structure in the
prospect area. Its axis more or less passes through Dorje Khola. The mineralization bands are clearly visible and can
be traced only in the eastern limb and crest of the anticline. Whereas only
isolated local patchy mineralization is recorded at Salleni in the western
limb. Few local transverse faults e.g. Arubote fault, Kopu fault, Singati fault,
Ghyangdada fault, Barappu fault and Kapase faults
have locally affected the mineralized body and displaced it at certain distance.
MINERAL EXPLORATION
Mineral
exploration activities includes detail topographic survey (1:1000scala), Semi
detail (1:16,000 and 1:10,000 scale) and Detail Geological Mapping
(1:1000scale), Trenching Pitting, Chip/ Channel, Bulk and Grab sampling of the
ore and get them analyzed to know the iron content in them. Ore
Trenching, Pitting and Ore
The
hematite ore body is not exposed throughout the prospect area. Therefore to
expose the ore body/ mineralization bands and collect fresh and representative
ore samples, altogether 1792.5m3 (35 Trenches and 15 Pits) earth materials were excavated (Fig.4, 9, 10) during 4 different stages of exploration. On the
whole about 86 channel, 123 chip, 74 grab samples, and 55 bulk samples from the
ore bodies were collected for microscopic study, chemical analysis and
metallurgical testing. Simple beneficiation test of 17 bulk/ grab ore samples were
carried out to upgrade the quality of the ore.
Mineralization
Scattered small scale mines were in operation by
local minors for about 100 years but no proper geological study of deposit was
carried out before in spite of many visits of Mining Engineers and
Metallurgists of than Bureau of Mines. For the first time Kaphle and Khan from
DMG did the preliminary geological assessment of Thoshe Iron prospect in 1995.
In the following year (1996) they did the Preliminary Follow up exploration and
assessment of the deposit and prepared a Semi-detail Geological map of Thoshe
iron prospect and surrounding area at 1: 16,000scale, and also tried to trace
the mineralized ore body by compass - tape survey /
Fig.9: Mineralized bands exposed by Trench-10 in Kopu
Devithan, Trench-8, Kopu Bhalukuna, and Pit in Arubote.
Fig.10: Pit dug to expose ore body in
Ghyangdanda. Fig.11: Part Barappu old working site
traverse as well as by digging 16
trenches and 2 pits. Only after these studies it is clearly known that Thosey iron deposit occurs within the
low dipping chloritic mica schist (Host rock) of Dorje Khola Formation. It is
overlain by calcareous mica schist locally with silicious crystalline dolomite/
marble and underlain by green chloritic sericitic mica schist and carbonaceous
chloritic schist (Fig.4). The mineralized bands lie on
the upper most part of the chloritic sericitic quartz mica schist. At places, especially in Bhosbhose, Singati, Ghyangdada and Barappu area (Fig.10 & 11) the mineralized body is
covered either by loose residual soil or collapse earth materials and old
mining dumps.
Detail
geological mapping of the deposit was able to trace shining silver gray 2 - 3m thick hematite
bodies (locally with some magnetite) which are at places combined as one and
other places two to three as separated by few cm to 6m thick incipiently
mineralized ferruginous sericitic quartz mica schist and green chloritic mica
schist bands. Therefore, the combined thickness of the ore body appears to be
around 2.5 - 3m thick which can be traced over 5km strike length from Arubote
to Singati (4km) and from Singati to Barappu (1km). The ore body was exposed by
digging more than 35 shallow trenches and 15 pits as well as with the help of
existing old working pits scattered within a 30m to 70m wide zone along the
mineralization bands (at Arubote, Silili, Sanodadakharka/Patale, Dadakharka,
Kopu Bhalukuna, Kopu, Pahare, Jhoreni, Kuwakopakha, Bhosbhose, Singati,
Ghyangdada and Barappu (Fig. 2, 3, 4, 9, 10, 11).
Iron concentration within the ore body is not uniform and varies considerably
from 20 to 66%. However, for reserve calculation only the ore having >30%
iron is taken as ore. Kaphle and Khan (1995 & 1996) have also analyzed few
selected samples for Ag, Ni, Ti, and Cr (Table-2). The iron content in the ore
appears better in Arubote, Singati and Barappu as compared to Ghyangdada,
Bhosbhose, Jhoreni and Pahare. Hematite mineralization are also known from nearby
areas at Salleni, Dangadinger, Sotre and Ghunsa area which is yet to be studied
in detail.
Nature of Mineralization
In
Thoshe three types of nature of mineralization are observed as (1) The massive
to poorly foliated hematite with some crystalline magnetite (medium to high
grade ore), (2) Foliated specular hematite with few thin sericite and quartz
lamina (low to medium grade ore), and (3) Incipiently mineralized foliated
micaceous hematite (low grade ore/ schistose hematite). Second type of
mineralization is more common in Thoshe deposit. Iron content in first type is
comparatively higher than the other two types. The mineralized bands/ bodies
are well exposed in Jhoreni, Pahare, Kopu Bhalukuna, Kopu Devisthan,
Sanodadakhark (Patale), and partly in Arubote. But in other localities like in
Kuwakopakha, Bhosbhose, Singati, Ghyangdanda, Barappu and part of Arubote
mineralized bands are covered either by thick residual soil or by thick old
mine dump and slided debris materials. 4 to 20m deep pits are required to hit
the mineralized band in this area.
Mineralization Bands
(a) Upper Mineralization Band
It
consists of 30cm to 1.5m thick, medium to coarse grained foliated shining silver
gray to brownish gray hematite (Fig.12 & 13) with cherry red streak and locally
lenses/ bands of shining steel gray to silver gray massive to poorly foliated magnetite
with gray streak. In Arubote and Sotre (outside the area) section some
pyrrhotite and pyrite are also recorded along with the quartz lenses in magnetite
that indicate some local hydrothermal effects as well. Highly magnetic massive
magnetite ore with minor association of pyrrhotite in Arubote are very rich in
iron (Up to 66%Fe). The upper mineralization band is separated from the lower
by a 32cm - 6m thick incipiently mineralized ferrugenous sericitic quartz mica
schist band.
(b) Lower Mineralization Band
It
is less than 1m to 2.15m thick, foliated, specular hematite band locally with
very few magnetites. It is rich in mineralization towards upper and lower part.
At places basal part is less mineralized. The thickness of mineralized body and
the concentration of iron in them vary considerably in different sections as
confirm by trenching (Fig.12 & 14). However, the ore minerals are the same
shining gray micaceous hematite with or without magnetite. At few places flaky
shining steel gray to silver gray ilmenite are recorded in some of the quartz +
ilmenite veins in the mineralized body.
Fig. 12: Upper & Lower Mineralization bands occur
together. Both are exposed by Trench No.8, in Kopu Bhalukuna
Fig.13: Upper Mineralization band (Tr.2) and Fig.14:
Lower Mineralization band (Tr-2) at Pahare Khani.
(c) Third Mineralization Band
According
to the local old people/ miners the third mineralization band is lying just
below the second mineralization band. It is 1.5 to 2.5 m thick and becomes rich
in iron content in Bhosbhose and Gairi Khani at Singati area. They also claim
that because of foliated and brittle nature of the specular hematite ore it can
be easily excavated in Singati and Bhosbhose. However, the investigations so
far carried out were not enough to trace the third possible mineralization band
due to thick overburden of overlying rock, old mine dumps, slided debris. It
needs deep trenching, tunnel drive or 75 – 120 m deep test drill holes to
confirm the thickness of the third mineralized body and its grad. Proposed
Geophysical exploration (Magnetic or IP survey) will be able to trace all the
mineralized bodies and also roughly tell about the size, shape and depth of
mineralization. Once it is traced and include in the calculation then the
overall geological ore reserve exceeds to 16milion tons.
(d) Ore
Study
of hematite ore under the ore microscope revealed that it consists of mainly
hematite (60-80%), magnetite (3-10%), iron sulphide (0 - 3%), ilmenite (0 -
<1%) as ore minerals and the gangue minerals (8 – 25%). Locally hematite is
replaced by magnetite. Chief gangue minerals are quartz, biotite, muscovite/
sericite and chlorite. Similarly massive magnetite consists of 65-85%
magnetite, 5-10% hematite, 0-3% Ilmenite and 0 – 4% iron sulphide. Quartz,
biotite, chlorite and sericite are the gangue minerals.
Field
observations combined with laboratory investigations and tests as well the nature
of the mineralization clearly revealed that it is a synsedimentary hematite
deposit which was later metamorphosed during regional metamorphism. As a result
the hematite has recrystallized into foliated micaceous shining silver gray specular
hematite with minor amount of magnetite in the south at Jhoreni, Bhosbhose,
Pahare and Kopu khani and gradually becomes less micaceous and locally more or
less massive hematite with few magnetite, pyrite and occasionally pyrrhotite in
Arubote area. It is a stratabound hematite (iron) deposit. Locally minor
hydrothermal effect has indicated by the presence of few small quartz veins and
quartz + magnetite and + ilmenite veins and lenses as well as quartz +
Pyrite ( + ) Pyrrhotite lenses within the hematite bands and lots of
quartz veins in the host rock very close to the contact with the mineralized
bands. The iron content in the ore body varies considerably from <30 to 66%Fe
locally with minor amount of other ferrous metals like titanium (up to
1600ppm), chromium (up to 50ppm), Nickel (up to 60ppm) and rare amount of
Silver (up to 2ppm. (Table-2 &3).
CHEMICAL ANALYSIS RESULTS
Four
types of ore samples (Channel, Chip, Bulk and Grab samples) were collected from
exposed part of the mineralized body after excavating trenches and pits.
Depending on the concentration of iron in the ore (visual expression), samples
were selected and crushed and pulverized to minus -80mesh and analyzed to know
iron content in them.
Out
of 86 channel, 123 chip, 74 grab and 55 bulk samples only 143 samples were analyzed
in DMG Chemical laboratory and 6 samples in NESS
laboratory (for cross checking) and 17 samples in
Soil Test Laboratory to know the iron content in the ore. In all the three laboratories AAS method was used
for all the chemical analysis. Analytical results of 155 hematite ore samples are presented in Table-2, 3, 4 & 5. Beneficiation test of 17
ore samples to upgrade the ore quality was
possible (Table-5). The analytical results
indicate that the distribution of iron (iron content) in the ore is not uniform
and it varies considerably from 20 to 55%. However, Kaphle and Khan (1995/1996)
have reported up to 66% iron. Present study revealed that on average the grade
is just around 45.3%. Because of non-uniform
grade of the ore only selective mines could be possible. However, metallurgical
beneficiation of the low to medium grade ore should help to upgrade the quality
of the ore and make it possible to mine the whole deposit.
Table-2: Chemical Analysis of Hematite ore
samples from Thosey Prospect (DMG, Kaphle
and Khan 1996)
S.N.
|
Sample Number
(Chip/Channel samples)
|
Location/ Remarks
|
Fe (%)
|
Cr
ppm)
|
Ti
(ppm)
|
Ni
(ppm)
|
Ag (pap)
|
Remarks
|
||||
1
|
RM/2052/53
KK/Th/Jh/Tr-1/Cp-1
|
Jhoreni
Khani/ LG ore
|
32.50
|
-
|
-
|
-
|
-
|
Result
compiled
|
||||
2
|
“ “
Jh/Tr-1/Cp-2
|
Jhoreni
Khani/ LG ore
|
40.00
|
-
|
-
|
-
|
-
|
|||||
3
|
‘’ “ Jh/ Tr-1//Cp-3
|
Jhoreni
Khani/ LG ore
|
37.50
|
-
|
-
|
-
|
-
|
|||||
4
|
“ “
Ph/Tr-2/Cp-4
|
Pahare
Khani/ MG ore
|
42.50
|
-
|
-
|
-
|
<1
|
|||||
5
|
“ “
Ph/Tr-2/Cp-5
|
Pahare
Khani/ LG ore
|
37.50
|
-
|
-
|
-
|
<1
|
|||||
6
|
“ “
Ph/Tr-2/Cp-6
|
Pahare
Khani/ MG ore
|
45.00
|
-
|
-
|
-
|
-
|
|||||
7
|
“ “
Ph/Tr-2/Cp-7
|
Pahare
Khani/LG ore
|
40.00
|
-
|
-
|
-
|
||||||
8
|
“ “ Ph/Tr-3/Cp-8
|
Pahare
Khani/ MG ore
|
47.50
|
-
|
-
|
-
|
-
|
|||||
9
|
“ “ Ph/Tr-3/Cp-9
|
" " "
|
45.00
|
-
|
-
|
-
|
-
|
|||||
10
|
" "Kp/Tr-5/Cp-10
|
Kopu
Khani/ LG ore
|
30.00
|
-
|
-
|
-
|
-
|
|||||
11
|
" " /Kp.Tr-5/Cp.11
|
Kopu
Khani/ LG ore
|
40.00
|
-
|
-
|
-
|
-
|
|||||
12
|
“ “’Kp/Tr-5/Cp-12
|
Kopu
Khani/ LG ore
|
40.00
|
-
|
-
|
-
|
-
|
|||||
13
|
“ “
“ Tr-6/Cp-13
|
Kopu
Khani / MG ore
|
32.50
|
-
|
-
|
-
|
-
|
|||||
14
|
“ “
“ Tr-7/Cp-14
|
Kopu
Khani/ MG ore
|
47.50
|
-
|
-
|
-
|
-
|
|||||
15
|
“ “
“ Tr-7/Cp-15
|
Kopu
Khani/ LG ore
|
32.50
|
-
|
-
|
-
|
-
|
|||||
16
|
“ “ Kp/Tr-7/Cp-16
|
Kopu
Khani/ MG ore
|
47.50
|
-
|
-
|
-
|
-
|
|||||
17
|
“ “
“ Tr-8/Cp-17
|
Kopu-Bhalu
Kuna/LG
|
32.50
|
-
|
-
|
-
|
<1
|
|||||
18
|
“ “
“ Tr-8/Cp-18
|
" " "
|
32.50
|
-
|
-
|
-
|
<1
|
|||||
19
|
“ “
“ Tr-8/Cp-19
|
" " "
|
4.00
|
-
|
-
|
-
|
<1
|
|||||
20
|
“
“ “ Tr-8/Cp-20
|
" "/ HG ore
|
52.50
|
-
|
-
|
-
|
<1
|
|||||
21
|
"
" Tr-9/Cp-21
|
" "/ LG ore
|
32.50
|
-
|
-
|
-
|
-
|
|||||
22
|
“ “
“ Tr-9/Cp-22
|
" "/ LG ore
|
37.50
|
-
|
-
|
-
|
-
|
|||||
23
|
“ “
“ Tr-10/Cp-23
|
Kopu
Devisthan/ LG ore
|
30.00
|
-
|
-
|
-
|
2
|
|||||
24
|
“ “
“ Tr-10/Cp-24
|
" "/ MG ore
|
45.00
|
-
|
-
|
-
|
<1
|
|||||
25
|
“ “
Dk/Cp-25
|
Dandakharka/
LG ore
|
35.00
|
-
|
-
|
<1
|
||||||
26
|
“ “
Dk/Cp-26
|
" "/ LG ore
|
35.00
|
-
|
-
|
-
|
-
|
|||||
27
|
“ “
Dk/Cp-27
|
" "/ MG ore
|
45.00
|
-
|
-
|
-
|
-
|
|||||
28
|
“ “ SDkTr-12/Cp-28
|
Sano
" " / LG ore
|
40.00
|
-
|
-
|
-
|
-
|
|||||
29
|
“ “
Tr-12/Cp-29
|
" " "/ LG ore
|
37.5
|
-
|
-
|
-
|
-
|
|||||
30
|
“ “ “
Tr-12/Cp-30
|
" " "/LG ore
|
35.00
|
-
|
-
|
-
|
-
|
|||||
31
|
“ “ “
Tr-13/Cp-31
|
" " " / LG ore
|
37.50
|
-
|
-
|
-
|
<1
|
|||||
32
|
“ “ “
Tr-13/Cp-32
|
" " " / LG ore
|
40.00
|
-
|
-
|
<1
|
||||||
33
|
“ “ Sl//Pt-1//Cp-33
|
Silili
/ HG ore
|
50.00
|
-
|
-
|
<1
|
||||||
34
|
“
“ Sl/Pt-1/Cp-34
|
“ “ / HG
ore
|
52.50
|
-
|
-
|
<1
|
||||||
35
|
“
Ab/Tr-14/Pt-2/Cp-35
|
Arubote/
LG ore
|
27.50
|
-
|
-
|
-
|
||||||
36
|
“
“Ab/ Tr-14/Cp-36
|
Arubote
Khani/ HG ore
|
52.50
|
-
|
-
|
-
|
||||||
37
|
“
“ Tr-14/ Cp/36A
|
" " / LG ore
|
33.70
|
-
|
-
|
-
|
-
|
|||||
38
|
“
“ Tr-15/Cp-37
|
" " / HG ore
|
55.00
|
-
|
-
|
-
|
-
|
|||||
39
|
“ “ Tr-15/Cp-38
|
" " / MG ore
|
45.00
|
-
|
-
|
-
|
-
|
|||||
40
|
“
“Tr-15/Cp-39
|
" " / HG ore
|
55.00
|
-
|
-
|
-
|
<1
|
|||||
41
|
KK/Th
/Cps-16A
|
" " / LG ore
|
40.00
|
-
|
-
|
-
|
-
|
|||||
42
|
KK/Boll/Cps-40
|
Guns/
LG(?)
|
20.00
|
-
|
-
|
-
|
-
|
|||||
43
|
KK/Th
/Sll/Cp-41
|
Salleni
Khani/ MG ore
|
47.50
|
-
|
-
|
-
|
<1
|
|||||
44
|
KK/Th
/Sll/Cp-42
|
" " / LG ore
|
27.50
|
-
|
-
|
-
|
<1
|
|||||
45
|
KK/Bml /Cps-43
|
Barmasthali/
HG ore
|
55.00
|
-
|
-
|
-
|
-
|
|||||
46
|
Cp-44
|
(?0
|
NA
|
-
|
-
|
-
|
-
|
|||||
47
|
CP-45
|
(?)
|
37.50
|
-
|
-
|
-
|
-
|
|||||
Bulk Samples
|
Location/Remarks
|
-
|
||||||||||
48
|
KK/Th
/Jr/Tr-1/Blk-1
|
Jhoreni
Khani/ LG ore
|
31.50
|
-
|
-
|
-
|
-
|
|||||
49
|
" " Ph/Tr-2/Blk-2A
|
Pahare
Khani /MG ore
|
42.50
|
-
|
-
|
-
|
-
|
|||||
50
|
" " Ph /Tr-2/Blk-2B
|
Pahare
Khani/ LG ore
|
40.00
|
-
|
-
|
-
|
-
|
|||||
51
|
" "
Kp/Tr-5/Blk-3A
|
Kopu " / MG ore
|
42.50
|
-
|
-
|
-
|
-
|
|||||
52
|
" "
Kp/Tr-5/Blk-3B
|
Kopu " / LG ore
|
40.00
|
-
|
-
|
-
|
-
|
|||||
53
|
" "/ Kp/Tr-7/Blk-4A
|
Kopu “ /LG ore
|
35.00
|
-
|
-
|
-
|
-
|
|||||
54
|
" " Kp/Tr-8/Blk-5A
|
Kopu
Bhalukuwa/LG ore
|
32.50
|
-
|
-
|
-
|
-
|
|||||
55
|
" " Kp/Tr-8/Blk-5B
|
" " / LG ore
|
22.50
|
-
|
-
|
-
|
-
|
|||||
56
|
" " /Kp/Tr-8/Blk-5C
|
Kopu
Bhalukuwa/ MG ore
|
45.00
|
-
|
-
|
-
|
-
|
|||||
57
|
" " /Kp/Tr-10/Blk-6A
|
Kopu
Division/ LG ore
|
28.70
|
-
|
-
|
-
|
||||||
58
|
" "/Kp/Tr-10/Blk-6B
|
Kopu
Devithan/ LG ore
|
25.00
|
-
|
-
|
-
|
-
|
|||||
59
|
" Sd/Tr-11/Blk-7
|
Sanodadakharka/
LG ore
|
37.50
|
-
|
-
|
-
|
-
|
|||||
60
|
" "/Sd/Tr-12/Blk-8
|
Sanodadakhark/
LG ore
|
33.75
|
-
|
-
|
-
|
-
|
|||||
61
|
" " /Sil/Tr-13/Blk-9
|
Silili
Khani/ LG ore
|
22.50
|
-
|
-
|
-
|
<1
|
|||||
62
|
" " /Ab/Tr-14/Blk-10
|
Arubote
Khani (?)
|
NA
|
-
|
-
|
-
|
-
|
|||||
63
|
" " " Tr.16 Blk-11
|
Arubote
|
NA
|
-
|
-
|
-
|
-
|
|||||
Table-3:
Analytical Results of Grab Samples (DMG, Kaphle and Khan, 1995)
|
||||||||||||
S.N.
|
Sample Number
|
Location
|
Fe(%)
|
Cr (ppm)
|
Ti
(ppm)
|
Ni
(ppm)
|
Ag (ppm)
|
Remarks
|
||||
64
|
RM/2051/052 KK/S-6A
|
Arubote
Khani
Very High grade ore
|
66.00
|
-
|
<800
|
40
|
-
|
Near
Tr-14
|
||||
65
|
“
KK/S-6B
|
Arubote
Khani/ MG ore
|
45.00
|
NA
|
1600
|
60
|
NA
|
Near
Tr-13
|
||||
66
|
“ KK/S-8A
|
Pahare
Khani/ HG ore
|
57.00
|
40
|
<800
|
40
|
NA
|
|||||
67
|
“
KK/S-8A-1
|
Pahare
Khani/ MG ore
|
48.00
|
40
|
800
|
50
|
NA
|
|||||
68
|
“
KK/S-8B
|
Pahare
Khani/ LG ore
|
31.00
|
-
|
<800
|
40
|
-
|
|||||
69
|
“
KK/S- 23A
|
Bhosbhose
Khani/ LG ore
|
30.50
|
-
|
-
|
-
|
-
|
|||||
70
|
“
KK/S- 23B
|
Bhosbhose
Khani/MG ore
|
49.50
|
-
|
1600
|
-
|
-
|
|||||
71
|
“
KK/S- 23C
|
Bhosbhose
Khani/MG ore
|
50.00
|
50
|
<800
|
-
|
-
|
|||||
72
|
“
KK/S- 25
|
Singati
Khani/ MG ore
|
45.00
|
-
|
-
|
-
|
-
|
|||||
73
|
“
KK/S- 26
|
Singati
Khani/ MG ore
|
45.00
|
-
|
-
|
-
|
-
|
|||||
74
|
“
KK/S- 26A
|
Singati
Khani/ LG ore
|
34.00
|
30
|
<800
|
20
|
-
|
|||||
5
|
“
KK/S- 28
|
Barappu
Khani/ LG ore
|
38.00
|
-
|
-
|
-
|
-
|
|||||
76
|
“
KK/S - 30
|
Salleni
Khani/ LG ore
|
31.50
|
-
|
-
|
-
|
-
|
|||||
77
|
“
KK/S - 30A
|
Salleni
Khani/ LG ore
|
NA
|
-
|
-
|
-
|
-
|
|||||
78
|
“
KK/S - 31
|
Pahare
Khani/ LG ore
|
33.50
|
-
|
-
|
-
|
-
|
|||||
79
|
“
KK/S - 32
|
Pahare
Khani/ LG ore
|
NA
|
-
|
-
|
-
|
-
|
|||||
80
|
“
KK/S - 34
|
Jhoreni
Khani/ LG ore
|
32.00
|
-
|
-
|
-
|
-
|
|||||
81
|
“
KK/S - 35
|
Jhoreni
Khani / LG ore
|
40.00
|
-
|
-
|
-
|
-
|
|||||
82
|
“
KK/S - 36
|
Kuwa
Khani/ MG ore
|
43.00
|
-
|
800
|
-
|
NA
|
|||||
83
|
“ KK/S - 38B
|
Pahare
Khani/ LG ore
|
34.50
|
-
|
-
|
-
|
-
|
|||||
84
|
“ KK/S - 39A
|
Darim
Danda/ MG ore
|
42.00
|
-
|
800
|
40
|
-
|
|||||
85
|
“ KK/S - 39B
|
Darim
Danda/ LG ore
|
40.00
|
-
|
-
|
-
|
-
|
|||||
86
|
“ KK/S - 41
|
Kopu
Khani/ LG ore
|
29.50
|
800
|
-
|
|||||||
87
|
“ KK/S -42A
|
Kopu
Bhalukuna/ LG ore
|
37.00
|
-
|
-
|
-
|
-
|
|||||
88
|
“ KK/S -42B
|
Kopu
Bhalukuna/ HG ore
|
55.50
|
-
|
800
|
-
|
-
|
|||||
89
|
“ KK/S -43
|
Kopu
khani/ LG ore
|
38.00
|
-
|
-
|
-
|
-
|
|||||
90
|
“ KK/S
-66
|
Silili
Khani/ LG ore
|
NA
|
-
|
-
|
-
|
-
|
|||||
91
|
“ KK/S
-67
|
Sano
Dandakharka/MG ore
|
49.50
|
50
|
<800
|
<20
|
-
|
|||||
92
|
“ KK/S-
67A
|
Sanodandakharka/LG
ore
|
35.00
|
-
|
-
|
-
|
-
|
|||||
93
|
“ KK/S-
70
|
Danger
Dinger/ LG ore
|
31.50
|
-
|
-
|
-
|
-
|
|||||
94
|
“ KK/S-
78
|
-
|
-
|
-
|
-
|
-
|
-
|
|||||
95
|
“
KK/S- 001
|
-
|
-
|
-
|
-
|
-
|
-
|
|||||
96
|
“ KK/S-
117
|
-
MG ore
|
-
|
-
|
-
|
-
|
-
|
|||||
97
|
“ KK/S
-141B
|
-
LG ore
|
-
|
-
|
-
|
-
|
-
|
|||||
Ch = Channel sample, Cp = Chip sample, Blk = Bulk sample, S = Grab sample, Low grade =31- 40%Fe, MG =
Medium grade = 41- 50%Fe, HG =High grade = 51-60%Fe, Very High grade >60%Fe.
Table-4: Chemical Analysis of the Ore
S.N.
|
Sample No.
|
Location
|
Sample type
|
Thickness
of channel(m)
|
Fe Content (%)
DMG Lab
|
Fe % after Beneficiation
|
Remarks
|
1
|
TH/TR-1/Ch-1
(TR-8)
|
Pahare Khani
(Kopu Bhalukuna)
|
Channel
|
0.46
|
45.16
|
-
|
Medium
|
2
|
TR-1/Ch-2
|
Pahare Khani
|
Channel
|
0.32
|
32.67
|
-
|
Low
|
3
|
TR 1/Ch-3
|
Pahare Khani
|
Channel
|
0.30
|
42.28
|
-
|
Low – Med
|
4
|
TR-1/Ch-4
|
Pahare Khani
|
Channel
|
0.30
|
37.58
|
-
|
Low
|
5
|
TR-1/Ch-5
|
Pahare Khani
|
Channel
|
0.36
|
45.87
|
-
|
Medium
|
6
|
TR-1/Ch-6
|
Pahare Khani
|
Channel
|
0.40
|
51.94
|
-
|
Med – High
|
7
|
TR-1/Ch-7
|
Pahare Khani
|
Channel
|
0.44
|
47.15
|
-
|
Medium
|
8
|
TR-2/ Cp-1
(TR-6)
|
Pahare Khani
(Kopu Khani)
|
Chip
|
0.50
|
10.63 (?)
|
-
|
Very low/ Recheck
|
9
|
TR-3/Ch-1
(TR-15)
|
Arubote Khani
|
Channel
|
0.68
|
39.94
|
-
|
Low
|
10
|
TR-3/Ch-2
|
Arubote Khani
|
Channel
|
0.40
|
51.52
|
-
|
Med - high
|
11
|
TR-4/Ch-1
(TR-12)
|
Arubote Khani
(Sanodadakharka
|
Channel
|
0.48
|
49.01
|
-
|
Medium
|
12
|
TR-5/Ch-1
(TR-11)
|
Arubote Khani
(Sanodadakharka)
|
Channel
|
1.50
|
16.89 (?)
|
-
|
Very low/ Recheck
|
13
|
TR-6/Ch-1
(TR-10)
|
Pahare Khani
(Kopu Devithan)
|
Channel
|
0.60
|
29.56
|
-
|
Low grade
|
14
|
TR-6 /Ch-2
|
Pahare Khani
|
Channel
|
1.14
|
30.18
|
-
|
Low grade
|
15
|
TR-6/Ch-3
|
Pahare Khani
|
Channel
|
0.40
|
46.22
|
-
|
Medium
|
16
|
TR-6/Cp-1
|
Pahare Khani
|
Chip
|
0.60
|
42.54
|
-
|
Medium grade
|
17
|
TR-7/Ch-1
(TR-5)
|
Kopu Khani
|
Channel
|
0.40
|
43.37
|
-
|
Medium grade
|
18
|
TR-7/Ch-2
|
Kopu Khani
|
Channel
|
0.36
|
45.26
|
-
|
Medium
|
19
|
TR-8/Cp-1
(TR-4)
|
Kopu Khani
|
Chip
|
0.30
|
34.51
|
-
|
Low grade
|
20
|
TR-9/Ch-1
(TR-2)
|
Kopu Khani
(Pahare Khani)
|
Channel
|
0.36
|
29.15
|
-
|
Low grade
|
21
|
TR-9/Ch-2
|
Kopu Khani
|
Channel
|
0.28
|
45.13
|
-
|
Medium
|
22
|
TR-9/Ch-3
|
Kopu Khani
|
Channel
|
0.30
|
43.45
|
-
|
Low – Med
|
23
|
TR-9/Ch-4
|
Kopu Khani
|
Channel
|
0.32
|
34.62
|
-
|
Low grade
|
24
|
TR-10/Ch-1
(Tr-7D)
|
Pahare Khani
(Kopu Khani)
|
Channel
|
1.00
|
34.77
|
-
|
Low grade
|
25
|
TR-10/Ch-2
|
Pahare Khani
|
Channel
|
0.36
|
49.52
|
-
|
Medium
|
26
|
TR-10/Ch-3
|
Pahare Khani
|
Channel
|
0.20
|
34.95
|
-
|
Low grade
|
27
|
TR-11/Cp-1
(TR-7C)
|
Pahare Khani
(Kopu Khani)
|
Chip
|
0.36
|
49.07
|
-
|
Medium
|
28
|
TR-11/Cp-2
|
Pahare Khani
|
Chip
|
0.34
|
44.87
|
-
|
Medium
|
29
|
TR-12/Ch-1
(TR-7B)
|
Pahare Khani
(Kopu Khani)
|
Channel
|
0.48
|
38.66
|
-
|
Low grade
|
30
|
TR-12/Ch-2
|
Pahare Khani
|
Channel
|
0.42
|
39.22
|
-
|
Low grade
|
31
|
TR-13/Ch-1
(TR-7A)
|
Pahare Khani
(Kopu Khani)
|
Channel
|
0.90
|
42.08
|
-
|
Low -Med
|
32
|
Pt.1/Cp-1
(Pit3)
|
Jhoreni
|
Chip
|
0.50
|
44.54
|
-
|
Medium
|
33
|
TH/S-53
|
Jhoreni Khani
|
1.00 (?)
|
53.33
|
-
|
Med - High
|
|
34
|
TH/S-55
|
Singati Khani
|
1.00 (?)
|
52.34
|
-
|
Med - High
|
|
35
|
TH/Bds-75
|
Singati Khani
|
x
|
48.59
|
-
|
Medium
|
|
36
|
TR-1/Ch/Blk-2*
|
Pahare Khani
|
Bulk
|
(6kg)
|
NA
|
Report not received
|
Ch
= Channel Sample Cp = Chip
Sample Blk = Bulk Sample * Bulk sample from total channel
Very high = >60% High = 56 - 60% Med = 41 - 55% Low = 31 - 40% Very Low <30%
Note:
All samples were analyzed by AAS method.
BENIFICIATION AND METALLURGICAL TESTS
Upgrading of the low to medium grade hematite ore
of Thoshe by a cheap and simple beneficiation technique is necessary to prove
it as an economic deposit. Therefore, a simple beneficiation (crushing and
washing) method was applied at small scale to upgrade few ore samples. By this
method it was possible to remove some unwanted gangue minerals like mica and
quartz to upgrade hematite ore. Such simple beneficiation tests of 17 selected
samples were performed by hand crushing and washing of the crushed sample to
remove 20 to 30 % of gangue minerals from the original ore sample with a view
to upgrade the ore. This process was successful to upgrade the ore of 42%Fe to
50%Fe, 45%Fe to 60%Fe, 47.5%Fe to 60%Fe and 50.5%Fe to 62.5% Fe (Table-5). It is
also known that the Metallurgical beneficiation test of bulk iron ore
samples (Fe = 48.4%) carried out by UNDP, MED/ DMG, Nepal, National Mineral
Development Corporation Limited, Hyderabad, India in September 1987, could
upgrade it first up to Fe = 54.22% and Pilot scale Beneficiation up to 63.04%
Iron (Manandhar 2044BS) which is quite suitable to produce sponge iron.
Table-5: Ore
S.N.
|
Sample no.
|
Sample Type
|
Iron
content %
(Before
beneficiation)
|
Iron
content % (After beneficiation)
|
Remarks
|
1
|
TH/Tr-1/Ch-1-7
(7
samples mixed)
|
Bulk
ore
sample
|
45.00
|
50.00
|
Out
of 1700g only 1000g washed to 750g
|
2
|
TH/Tr-3-6/Ch-1-3
(3
samples mixed)
|
“
|
42.00
|
50.00
|
Out
of 200 only 1000g washed to 750g
|
3
|
TH/Tr-7-9/Ch-1-3
(3
samples mixed)
|
“
|
45.00
|
60.00
|
Out
of 1500g only 1000g washed to 850g
|
4
|
Tr-10&12/Ch1-4
(4
samples mixed)
|
“
|
42.0
(?)
|
47.50
|
Out
of 1550g only 1000g washed to 800g
|
5
|
TH/Tr.1/Ch-Blk
|
‘
|
47.50
|
60.00
|
Out
of 1000 all 1000g washed to 800g
|
6
|
TH/Tr-7&9/Ch2
2
samples mixed)
|
“
|
52.50
(?)
|
62.5
|
Out
of 1000g all 100g washed to 650g
|
7
|
TH/Tr-11/Blk-7
|
37.50
|
Analysis
in process
|
Out
of 500g all 500g washed to 300g (Sanodadakhark)
|
|
8
|
TH/
Blk/S-36
|
“
|
43.00
|
" "
|
Out
of 500g all 500g washed to 400g Jhoreni
|
9
|
TH/
Tr-5/Blk
|
“
|
43.37
|
" "
|
Out
of 500g all 500g washed to 400g (Kopu)
|
10
|
TH/Grab/S-55
|
“
|
52.34
|
" "
|
Out
of 500g all 500g washed to 400g
(Singati)
|
11
|
TH/Pt.6/
S-401
|
Bulk
sample
|
47.50
|
55.00
|
Out
of 500g all 500g washed to 400g (Singati West)
|
12
|
TH/Pt.7/S-402
|
“
|
40.00
|
45.00
|
Out
of 500g all 500g washed to 400g (Ghyangdada East)
|
13
|
TH/Pt.9/S-405
|
“
|
52.50
|
60.00
|
Out
of 500g all 500g washed to 400g Barappu
|
14
|
TH/Pt.4/S-406
|
“
|
52.50
|
55.00
|
Out
of 500g all 500g washed to 400g (Bhosbhose)
|
15
|
TH/Pt.5/S-408
|
“
|
50.00
|
57.00
|
Out
of 500g all 500g washed to 400g (Singati East)
|
16
|
TH/Pt.2/S-413
|
“
|
47.50
|
57.00
|
Out
of 500g all 500g washed to 350g (Arubotedil)
|
17
|
TH/Pt.8/S-415
|
“
|
52.50
|
55.00
|
Out
of 500g all 500g washed to 400g (Ghyangdada West)
|
Note:
Sample analyzed by AAS method in Soil Test Laboratory.
These results
are the positive indication for Thoshe iron deposit. However, it is necessary to
conduct additional beneficiation and metallurgical testing of the ore
(industrial testing) in one of the well known metallurgical laboratory. All
these test results will help to the company for economic calculation and make
the deposit feasible for mining.
GEOLOGICAL ORE
During Third
Phase of investigation Topographic map (at 1:1000 scale), Detail Geological map
and cross sections at the same scale were prepared and traced the south and
westward continuation of the mineralized body from Jhoreni to Kuwakopakha,
Bhosbhose and Singati in the south and from Singati east, Singati west,
Ghyangdada and Barappu to the west. The mineralization band is not exposed in
this area. However, presence of numerous old working pits within a strip/ zone
of 30 to 70m width and their cleaning works helped us to trace the mineralized
body almost throughout. Chemical analysis of the ore from Barappu, Ghyangdada
and Singati show that the ore contains up to 52.50%, 46.25% and 50.00% iron respectively. Now the left out Jhoreni - Kuwakopakha- Bhosbhose
sector (strike length 600m) and then Singati - Ghyangdada - Barappu sector
(strike length 1025m) were added and recalculated for possible Geological
reserve. The available data of Singati - Ghyangdada - Barappu sector and calculation
clearly indicates that additional 4.536 million
tons of iron ore is possible in this sector.
On the basis of the topography, overburden, mining
condition, nature of the mineralization and the analytical results the whole
Thoshe iron deposit area is divided into 3 major Blocks e.g. (1) Arubote -
Sanodadakhark Block (2) Dadakharka - Bhosbhose Block and (3) Singati - Barappu Block
for present calculation of the possible Geological ore reserve and average grade
of the ore in each block. All the results of these three blocks are combined
(3.74, 7.63 and 4.54 million tons respectively) and recalculated as possible
total geological ore reserve as 15.91 million tons ore with an average grade of
45.3% iron.
FINDINGS
The
preliminary and follow up investigation/ exploration of Thoshe iron deposit is
able to confirmed that it is the oldest known iron deposit in Nepal which was mined
by the local miners for a long time in the past. Over 1000 iron old working
pits and few smelting places with scattered slag are the solid proof old mining
activities.
Three
stages of exploration of Thoshe iron deposit was completed except test drilling.
Topographic map of 100 hectare at 1:1000 scale and a detail geological map of
the same area in the same scale are prepared. 35 Trenches and 15 Pits were
excavated to expose the ore body and collect fresh ore samples for laboratory
tests.
On
the basis of the nature of the ore, chemical analysis results of all the
samples, geological ore reserve and its grade is calculated as 15.91million tons
with an average of 45.3% iron.
1
- 3 m thick iron ore body with almost 5km strike length are well traced by
geological mapping, trenching and pitting. It is clear that the iron content in
the mineralized body is not uniform. Analytical results of the ore samples show
that the iron content varies considerably from 30% to 66% and combined overall average
is about 45.3%. Therefore, further upgrading of low and medium grade ore by
beneficiation (metallurgical process) and its industrial testing is necessary
to produce Sponge iron which can be used in iron and steel industries and to
judge whether the mining is feasible or not.
Simple
beneficiation of different types of representative ore samples from different
sectors of Thoshe iron deposit indicate that upgrading of Thoshe Hematite ore
up to certain percent is possible e.g. from 52 to 63% iron. Therefore, it is
hoped that proper mechanical beneficiation would be able to upgrade up to 63%
which is quite suitable for the production of sponge iron.
Possible
site for ore storage, beneficiation, metallurgical treatment plant and other
industrial set up as well as possibility to generate electricity from the near
by rivers and tributary streams for industrial use were also looked for and
satisfactory places are identified.
RECOMMENNDATION
It
is a synsedimentary iron deposit which was later affected by regional
metamorphism. Iron ore is a shining silver gray specular hematite locally with
some massive magnetite and rare amount of ilmenite. The nature of the
mineralization, its extension length, combined thickness and over all tonnage
of the deposit appears to be suitable for mining. However, it is necessary to
upgrade the ore to >60%Fe by simple and cheap beneficiation method. It is
recommended to make its use in iron and steel industries and small part in
cement industries.
Topographical
and geological condition of the deposit in (1) Arubote - Silili -
Sanodadakharka Sector and (2) Singati - Ghyangdada - Barappu sector is suitable
for opencast mining although 5 to 18m thick overburden of residual soil,
collapse loose materials and some rock mass have to be removed during mine
development process. The rest part (3) Dandakhark - Kopu - Pahare - Jhoreni -
Bhosbhose area underground mining is recommended.
Geophysical
exploration (Magnetic/ IP) is recommended to trace the mineralized body and
find out its tentative shape and size at depth. It helps not only to confirm
the ore body at depth but also for locating drilling sites and also plan for
mine development. At the same time exploratory drilling (5 to 10 drill holes)
at a depth of 85 to 125 m is recommended to confirm the deposit and calculate
the ore reserve more precisely.
Basic
infrastructure like approach road, electricity line, water supply and telephone
facilities has to be improved to run heavy vehicles to transport heavy
machinery equipments, voluminous ore and other construction materials as well
as necessary power and water supply. Smelting of Hematite into a sponge iron requires
huge amount electricity or coal therefore, these things have to be considered well
in advance before start mining.
Overburden
materials and mine waste can be dump at the lower level in a very low angle to
almost flat ground around by constructing strong retaining wall to control
possible downward flow of the materials.
References
Adhikary, P.P. (1980), Reconnaissance geochemical and
geological mapping of a part of Dolakha
and Ramechhap district 72I/2 and I/6. MEDB/ DMG unpub. report GC/131/80.
N&C Minerals P. Ltd. (2008): Technical Report on Preliminary Follow up Prospection
(Phase-I) of Thoshe Iron Deposit Ramechhap district, Central
Nepal , pp.9, Report no TIP/1/2008.
N&C Minerals P. Ltd (2009): Technical report on
Follow up and Semidetail exploration (Phase II and Phase III) of Thoshe Iron Deposit,
Ramechhap, Central Nepal , pp.. Report no.
TIP/1/ 2009
Good, P.C. (1963), Report and
recommendation, Thoshe iron mines development.
Jhingran, A.G. (1961 ?)-
Report on Hematite in Those area.
Kaphle, K.P. and Khan, H.R.
(1996), Field Report on Preliminary
Follow up Exploration and Assessment of
Thoshe Iron Deposit, Ramechhap district, Central Nepal. DMG unpublished report
(p25).
Kaphle, K.P. and Khan, H.R. (1995), Geological Field
Report on Preliminary Assessment of Thoshe iron deposit Ramechhap District, Central Nepal . DMG, Unpublished report, (p11).
Kayastha, N.B. and Pradhan,
U.M.S. (1978), Report on Geology of Dolakha, Ramechhap area Eastern
Nepal , DMG
unpublished report.
Manandhar, G.R. (1963), Field
trip report on Wapsa copper mine , Solu East No.3 and Those iron mine, Thoshe, East No.2 NBM
unpublished report.
Manandhar, K.(2044BS) Trial
production of Sponge iron from Nepal Iron Ore. DMG un published report pp.20.
Rana, M.N. (1960), A scheme
on the establishment of an iron and steel industry in Nepal
Rana, M.N. (1964), Metallurgy
field trip report on Wapsa copper mine and Thoshe iron mine
(26p).
Rana, M.N. (1965),
Preliminary project report on Thoshe Iron works (19p).
Rana, M.N. (1966), Charcoal
for iron ore reduction in Nepal
Sing, S.P. (2030BS), Report on Phulchoki Iron ore
deposit (Exploration work conducted in
2028/29 and 2029/30. Unpublished report, Nepal Bureau of Mine.
*Suwal, R.N. (1965) Iron old
working in Thoshe.
Talalov, V.A. (1972), Geology
and Ores of Nepal vol.II.
*Upadhaya, R.P. (1956) Report
on Those iron deposit.
*Weise, R.O. (1960), Iron
foundry at Thoshe.
_____________________________________________________________________
Reference with * (star) is
not available in DMG
Figure Caption
Fig.1: Location
Map of Thoshe Iron Prospect Area, Ramechhap
district (Scale 1: 50,000).
Fig.2: Northern and Central Parts of Thoshe Iron Deposit (Arubote - Silili - Sanodadakharka - Kopu
Bhalukuna - Kopu - Pahare - Jhoreni -
Kuwakopakha -Bhosbhose Sector (Old working mine sites).
Fig.3: Singati - Ghyangdada - Barappu
sector of Thoshe Iron Deposit (Old working sites)
(Most part covered by Topographic Survey & Detail Geological
Mapping, 2009)
Fig.4:
Geological Map of Thoshe Iron Deposit
Fig.5: Iron
Chain (Sikri) made up of Thoshe Iron used in suspension bridge (lower level)
over Khimti River
Fig.6: Remnants of a Gun Factory to manufacture the barrels
of the guns from Thoshe Iron.
Fig.7A: Old Iron Ore Smelting Place
Fig.8:
Calc mica schist with crystalline dolomite/marble layers.
Fig.9: Mineralized
bands exposed by Trench-10 in Kopu Devithan, Trench-8, Kopu Bhalukuna, and Pit
in Arubote.
Fig.10:
Pit dug to expose ore body in Ghyangdanda.
Fig.11: Part
Barappu old working site
Fig. 12: Upper & Lower Mineralization bands occur
together. Both are exposed by Trench No.8, in Kopu Bhalukuna
Fig.13: Upper Mineralization band (Tr.2)
Fig.14: Lower Mineralization band (Tr-2) at Pahare Khani.
