Amerika Birleşik Devletleri Jeolojik Araştırmalar Kurumu (USGS), aşağıdaki tabloda gösterildiği gibi, krom içeriğine ve ilgili diğer özelliklerine göre farklı ticari kaliteleri sınıflandırmıştır.
TRANSFORMING VULNERABILITY INTO VALUE: A STRATEGIC ROADMAP FOR PAKISTAN’S CHROMITE INDUSTRY
INTRODUCTION TO CHROMITE:- Being the only viable commercial ore for extracting metallic grade of chromite, it is a brittle, dark grey to black mineral most commonly found in igneous and metamorphic rocks. Chemically it is an oxide mineral composed of iron, chromium and oxygen with its molecular formula as Cr2O3. The United States Geological Survey (USGS) has classified different commercial grades according to its chromium contents along with associated other properties as shown in the table below.
TYPES OF CHROMITE DEPOSITS: Based on the geological formation and shape, the globally existing chromite deposits are predominantly classified as Stratiform and Alpine/Podiform types. Stratiform types of deposits form massive, tabular and or sheet like bodies in large mafic to ultramafic igneous intrusions. They are commonly found as continuous interlayers within their specific host rocks stretching for kilometers linear distances, thereby constituting 98% of the current global chromite reserves. On the other hand the Alpine types of chromite deposits, vary widely in grade which occur as haphazardly shaped pods, lenses, pipes etc. in the ophiolite belts formed in oceanic crust and subduction zone settings.
PROJECTED GLOBAL MARKET OF CHROMITE BEYOND 2026: The global chromite requirement, according to the market experts is projected to undergo consistent expansion beyond 2026 mainly due to vast and rapid expanding stainless steel production and rapid infrastructural development in the Asia-Pacific region, particularly China, India, and Indonesia which accounts for over 60% of global chromite consumption. Other significant emerging opportunity in the chromite demand as forecasted by the experts is for specialty applications in aerospace, chemical catalyst and high performance pigments. Therefore In the light of aforementioned, and also by considering the supply-side constraints including geopolitical tension and environmental regulations, influencing market stability and pricing dynamics, the economic wizards have estimated a Compound Annual Growth Rate (CAGR) of chromite market beyond 2027 to 2033 between 5.59 to 9.33%
LOW GRADE CHROMITE ORES: It is a type of specified mineral aggregate that contains less than 40% chromium trioxide (Cr2 O3) which can not be used directly in industrial manufacturing without extensive processing for the reason that it contain a high concentration of unwanted impurities. Other key characteristics of a low grade chromite ore are that:
- Its Cr:Fe ratio is commonly below 1.5:1 making it inefficient for direct smelting into high-quality ferrochrome alloys.
- It is heavily mixed with gangue minerals like silica, alumina, iron oxides, serpentine, olivine and pyroxene.
- The chromite grains are frequently very finely scattered/disseminated through host rocks instead of being found in solid heavy lumps.
UPGRADATION OF LOW GRADE CHROMITE ORE - A PERVASIVE GLOBAL TREND: The speedily dwindling high-grade chromite deposits, rising stainless steel production, emerging high-tech applications like lithium ion battery cathods, resource sustainability etc. have forced the global mining industry to shift towards the upgradation of low-grade chromite ores and even ultrafine mine tailings to meet the growing demand of industrially required chromite concentrates of different categories. The low-grade ores typically being complex in their mineral composition, i.e. the individual chromite grains often trapped in silicate or serpentine matrices, are not susceptible to traditional simple washing or single upgradation process. Therefore depending upon the available low-grade chromite ore specific to a region are subjected to specialized upgradation techniques consequent to conducting lab./bench scale studies on selected predetermined low-grade chromite ore of the particular region and ultimately designng a flow diagram. The resultant flow diagram, specific for a particluar region is thus followed for establishing a commercial upgradation plant ensuring the maximum recovery and manimum wastage of chromite through tailing. Leading edge pathways being in practice in the aforementioned context after the comminution of chromite ore are the use of advanced gravity spiral concentrators, multi-gravity separators, advanced magnetic separators, wet high-intensity magnetic separators, dry high-intensity magnetic separators and even up to the extent of applying pyro metallurgical and chemical leaching upgradation process. The table given below portray essential technical details of several low-grade chromite upgradation plants presently in operation throughout in various parts of the world.
CHROMITE OCCURRENCES IN PAKISTAN: Predominantly the Alpine type, associated with ophiolitic rocks in their respective basal parts, emplaced along the colliding plate boundaries, chromite bodies are found as pods, lenses and irregularly shaped entities within the dunite as host rocks in Gilgit-Baltistan (GB), Khyber Pakhtunkhwa (KP) and Baluchistan Provinces of Pakistan. A run-down on the respective occurrences is as under:-
1) Chilas, (Diamer Dist. GB):- Chromite bearing ultramafic rocks have been reported near Chilas Town that forms a part of 300 km wide stratiform Chilas Complex within the Kohistan Island Arc. Though not yet explored, the Chilas chromite occurs in form of layers/stringers in the dunite having 26% Cr2 O3 content. On the basis of its structure and mineral chemistry has broader similarity with stratiform type, this so far uneconomic chromite occurrence is hypothetically ascribed as such rather than the alpine type.
2) Jijal (Lower Kohistan Dist. of KP):- Regarded as deep seated Island arc sequence, the rocks of the Jijal Complex are composed of various types of garnet gabros and ultramafic rocks. Several dozens of chromite lenses and pods within the ultramafic suit of rocks from this region have been reported with an estimated reserves of 0.6 million tons having a range of 40 to 45% Cr2O3 contents with Cr:Fe ratio as 2.8:1 to 3.6:1. Important chromite locations of the region are Jijal, Kokial, Shungial, Mani dara, Taghtai, Gabar, Kolai and Serai.
3) Sapat Gali (Dist. Mansehra, KP):-The so far unexplored Sapat complex consists of ultramafic rocks, layered meta-gabbro and gabbro-diorite. The primary chromite mineralization is in a 100 meter thick dunite rock unit and a broader 200 meter thick dunite-pyroxinite layer having chromium oxide around 47.55%
4) Malakand Chromite (Spreading over Dist. Malakand & Dist. Charsadda):- A 30km. east-west elongated, and 3 to 6km. wide obducted ophoilitic slice, known as the Dargai ophiolite complex host significant alpine type chromite ore bodies in the form of pods, lenses and veins. The Dargai ophiolite complex is represented by the oceanic crust of ultramafic rocks as harzburgite, dunite, chromitite, wehrlite, pyroxenite, serpentinite and a 1-2km. thick transition zone of mantle-crust rocks mainly gabbro.on zone of mantle-crust rocks mainly gabbro. These chromite ore bodies, range in Cr2O3 content from 20 to 55% which are being mined in several clusters notable among which are Heroshah, Upper Landi Rud, Badasar and Bajro Kanrhee having an estimated cumulative reserve of 0.67 million tons.
5) Dist. Mohmand, KP:- Thrust slices of ultramafic rocks, similar to Dargai ophiolite zone that may be the westward extension of the Dargai sequence contain lenses, pockets and disseminations of chromite in the ultramafic rocks near the villages of Parai, Yousaf Baba, Auro Khawar, Balala, Bucha and Mamanai Gudar. The region has not been adequately explored therefore it warrant extensive stage wise exploration up to the core drilling stage.
6) Dist. Bajaure, KP:- Chromite occurrences are primarily associated with the ophiolite sequence and ultramafic rock complexes exposed within the geographical boundaries of the Bajaure Dist. exposed along the Main Mantle Thrust zones passing across this District to the west in Afghanistan. Mined out in significant quantities from the locations namely Barang Tehsil, Asil, Targhao, Jurah, Kamangara and Hobani Sar with a recorded annual production of 1550 metric tons. This resource as so far noticed is mostly low grade, i.e. 15 to 30% Cr2O3.
7) Boya (Dist. N. Waziristan):- This Part of the KP Province holds significant and high potential chromite occurrences hosted in an ophiolite Complex specific to it. Chromite bearing ophiolitic rocks occurs west of Razmak, near Boya that is generally associated with the ultramafics and occurs as lenses, segregated stringers and disseminated grains. The chromite lenses are up to 6 meters long and 0.5 to 1.0 meters thick. The lenses are surrounded by a zone of ultramafic rocks up to 30 meters, containing high concentration of accessory chromite. Chromite occurrences have been reported from Mami Rogha, Sherkai, Madar Algad and Tut Nari. Detail exploration work is required to ascertain grade, reserves and workable deposits of the chromite occurrences.
8) The Zhob valley chromite, Districts. Quetta & Zhob, Balochistan:-Several dozen clusters of chromite occurrences are reported from the Zhob ophiolite complex which is a highly fragmented and exposed as three main detached blocks covering cumulative structural area of 150 to 200 square kilometer of exposed ophiolitic crust and mantle units. The larger outcrops are located in the vicinity of Khanozai and Muslim Bagh. The zhob valley chromite occurs in the serpentinized dunite of the ultramafic tectonites and cumulates in different forms and shapes. There are massive chromite ores surrounded by banded ores, grape-shot ores, banded deposits of disseminated ores, cigar-shaped ore bodies, dyke-like ore bodies up to 100 meters long and thin wiggly, irregularly shaped bodies invariably noticed from more than 350 currently operative mines. Being mined since the year 1903, major current operations are near Khanozai Muslimbagh, Saplai, Tor Ghar, Jang, and the Town of Zhob. The Cr2 O3 content of the Zhob chrome ores generally ranges from 37% to 55% with Cr::Fe ratio of 2.1:1 to 3:1.
9) Wad- Sonaro Chromite (Dists. Lasbela-Khuzdar, Balochistan):- Ranging in Cr2O3 contents betwen 38% and 54%, these chromite occurrences are located primarily within the Bela Opheolite Zone, being the largest one in Pakistan extending for a linear distance of 320 km. from the sea to the north across the Khuzdar and Lasbela districts of Balochistan yielding both metallurgical and refractory grades. The Bela ophiolitic complex is mainly comprised of mega-melanges which include fragments and blocks of ultramafics and lava flows. Lenticular or disseminated bodies of chromite are emplaced within the ultramafics, the major deposits of which are near Sonaro, Baran Lak, and Greshak areas of Khuzdar, where more than 15 pods have been identified which are being excavated through open pit mining operations.
CHROMITE MINING SECTOR OF PAKISTAN IS UNDER STAGNATION:- Pakistan holds immense high-grade podiform deposits with the associated low-grade chromite ores across the entire length of its known ophiolitic belts that rank it one of the major global producer and supplier of this mineral commodity. Regardless of the aforementioned fact it has become highly vulnerable to maintain its status as portrayed below by its 10 years production and supply trajectories. The primary obstacles linked to this stagnation inter alia include the following.
- Extraction of chromite is highly selective and being conducted through fragmented, small-scale surface mining or rudimentary underground "dogholes" instead of scientific three-dimensional mapping or core drilling. Consequently, this selective mining method has results in extensive mine waste dumps of low grade chromite as well as untouched low grade chromite deposits.
- Driven primarily by international demand rather than domestic industrial strategy, the sector is experiencing significant shifts influenced by global market changes
- As of now, Pakistan suffers from an overwhelming absence of modern domestic beneficiation (upgrading low grade ore to high-grade concentrate) or smelting plants. High grade ore is exported raw, while the lowe grade ores (which are high in silica) are frequently dumped or sold at throwaway prices because local processing facilities to separate the gangue minerals do not exist.
WAY FORWARD: In addition to the resource depletion, Pakistan's subsurface mining of high-grade chromite has gone very deep and expensive. This is due to the discontinuous nature of podiform deposits and sharply rising haulage costs. Expenses on mitigating and rehabilitating the complex environmental impacts related to under ground mining are yet another financial drain. Therefore upgrading of the surface, near surface and even waste mine dumps containing more than 10% Cr2O3 becomes inevitable for the chromite industry of Pakistan. In this context, it must be kept in mind that due to the unique nature of each deposit type-specifically its chemical and mineralogical composition and grain size liberation- the upgradation flow diagram must be designed after conducting laboratory scale/bench scale studies on bulk representative sample(s) of a particular region.
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