Targeting the hidden chromitite using geochemical vectoring for Bophivum area, northwestern Myanmar

2020 ◽  
Author(s):  
Chulho Heo ◽  
Ilhwan Oh ◽  
Seokjun Yang ◽  
Jaeho Lee ◽  
Sungwon Park ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Chromian Spinel ◽  
Melting Points ◽  
Portable Xrf ◽  
Al Content ◽  
Genetic Process ◽  
Ore Body ◽  
Reaction Result ◽  
Mantle Harzburgite ◽  
Podiform Chromitite

<p>Harzburgite are the rocks that make up the mantle and consist of olivine, orthopyroxene, and clinopyroxene (<5 %). Clinopyroxene contain Ca, Al, and Ti, while orthopyroxene contain Al. On the other hand, olivine contains almost zero contents of Ca, Al and Ti. When the rising melt from the lower mantle passes through the mantle harzburgite, the clinopyroxene and orthopyroxene with lower melting points compared with olivine are fused into the melt, and the olivine is crystallized from the melt. In this genetic process, harzburgite gradually change into dunite consisting of only olivine, and Ca, Al and Ti of pyroxene in harzburgite will escape into the melt. And, as the melting point of clinopyroxene is lower than that of orhopyroxene, the Ca, Al, and Ti in clinopyroxene are escaped into the melt earlier than those in orthopyroxene. The melt with changed composition formed by melting the pyroxene are mixed with the newly rising melt with pyroxene, so that the chromian spinel in the melt becomes saturated and the chromitite are formed. By the above-mentioned mechanism, chromitite occurs with dunite and pyroxene-deficient harzburgite formed by the reaction result between melt and harzburgite. In other words, in the genetic process of high Cr chromitite, the presence of melt that fused the pyroxene within harzburgite is essential. And, in order to make high Cr chromitite, the melt must have been fused more pyroxene in harzburgite. As a result, the Ti, Ca, and Al content of harzburgite will be decreased. Therefore, considering the representative chemical composition of podiform chromitite(Robinson et al., 1997), we assumed that as we approached into harzburgite bearing high Cr chromitite(probably hidden ore body), the Ti, Ca and Al content within harzburgite will be likely to converge toward the specific contents(Ti<180ppm, Ca<0.9%, Al<0.7%). In case of Bophivum chromitite in northwestern Myanmar, it corresponds well with the representative chemical composition of high Cr chromitite in terms of the above-mentioned data. Therefore, we monitored to see whether Ti, Ca, and Al contents systematically change by the distance from the center with chromitite outcrop or high Cr anomaly zone confirmed through soil and rock geochemical exploration toward the surrounding harzburgite outcrop or not and tried to select the target element for geochemical vectoring using portable XRF. Conclusively, Ca is considered to be a more meaningful geochemical vectoring indicator than Al in terms of portable XRF measurements in the survey area.</p>

scholarly journals MINERALOGY OF CHROMITITE, BULQIZA ULTRAMAFIC MASSIF, ALBANIAN OPHIOLITIC COMPLEX

2017 ◽  
Vol 43 (5) ◽  
pp. 2577
Author(s):  
A. Çina
Keyword(s):  
Physical Properties ◽  
Upper Mantle ◽  
Ore Body ◽  
Ultramafic Massif ◽  
Ore Bodies ◽  
Partial Fusion ◽  
Equilibrium Process ◽  
Mantle Harzburgite ◽  
Ophiolitic Complex ◽  
Different Parts

Ultramafic massif of Bulqiza belongs to Eastern Jurassic Albanian ophiolite belt of IAT-BSV- type. This massif is the most important chromite-bearing ore. The mantle ultramafics have extremely refractory nature. This is due to the high partial fusion of upper mantle which is depleted in CaO and Al2 O3 . The chromitite is situated to different parts of ultramafic pile, from bottom Cpx harzburgites up to massive dunites and cumulate ultramafic but the mainly chromite potential belongs to mantle harzburgite –dunite level and to transition dunites partly. The chromite is chiefly of Cr-rich metallurgical type. The atomic ratios of chromite , Fo of olivine and some physical properties of them vary according to the chromitite setting and reflects the evolution of Ol-Sp equilibrium process depended of the chromite concentration, from baren dunitic lenses towards dunite envelops of the ore bodies and the interstitial and inclusions of olivine within chromite grains. Two particular chromite deposits are the Bulqiza- Batra tabular folded ore body and Shkalla, pencil –like ore body.

Sur la notion de "types" de gisements metalliferes

1958 ◽  
Vol S6-VIII (3) ◽  
pp. 237-244
Author(s):  
Pierre Routhier
Keyword(s):  
Chemical Composition ◽  
Host Rock ◽  
Country Rock ◽  
Ore Deposits ◽  
Igneous Rocks ◽  
Ore Deposit ◽  
Ore Body ◽  
Enclosing Rocks

Abstract Limitations of existing classifications of ore deposits are examined, and a new "natural" classificationis proposed, based on "types." The types are based on the mineralogic and geologic characteristics of the ore deposit itself and of the host rock. Among the characteristics to be determined for the ore deposit itself are its hypogene paragenesis, superficial alteration, and the chemical composition and ore content of both the hypogene and supergene ore. The characteristics to be determined for the host rock relate to the lithology and stratigraphy of the enclosing rocks and the presence of contact alteration, if any; the form of the ore body in relation to the structure of the country rock; the nearby presence of igneous rocks; and age, if determinable. Descriptions can be completed by giving a list of examples of similar deposits with their age, if known, and pertinent genetic hypotheses.

Mineralogy and petrology of ultramafic section of Kukesi Massif, Mirdita Ophiolite (Albania) – preliminary results

2020 ◽  
Author(s):  
Jakub Mikrut ◽  
Magdalena Matusiak-Małek ◽  
Jacek Puziewicz ◽  
Kujtim Onuzi
Keyword(s):  
Chemical Composition ◽  
Chemical Diversity ◽  
Troodos Ophiolite ◽  
Melt Extraction ◽  
Al Content ◽  
Mantle Peridotites ◽  
Wide Range ◽  
Scientific Project ◽  
Composition Of Minerals ◽  
High Degree

<p>Mirdita Ophiolite in northern Albania is a part of 30-40 km wide ophiolitic Pindos Zone in Dinaride-Hellenide part of the Alpine orogenic system (e.g. Dilek & Furnes 2009, Lithos). Mantle and crustal sections in the eastern part of this zone have Supra-Subduction Zone geochemical affinities. The goal of our study is to examine chemical diversity of rocks within Kukesi Massif and to decipher its evolution.</p><p>The Kukesi Massif is composed mostly of coarse- to medium-grained spinel harzburgites and dunite with chromite layers (e.g. Morishita et al. 2011, Lithos), locally  cross-cut by orthopyroxenite veins. Uppermost part of the sequence consist of cumulate pyroxenites and peridotites (composed of olivine, orthopyroxene, clinopyroxene and spinel). Most of the rocks are pervasively serpentinised, but degree of serpentinisation varies within the massive. Samples of peridotites and pyroxenites from over a dozen localities within the massif were collected.</p><p>Olivine occurring in the lower sections of the ophiolite has composition of Fo<sub>89.5-91.2</sub> (NiO 0.28-0.52 wt.%) in peridotites and Fo<sub>90.6-92 </sub>(NiO 0.38-0.52 wt.%) in orthopyroxenite veins. Olivine forming cumulates has Fo<sub>82.4-83.3</sub> and NiO content=0.12-0.23 wt. %. Orthopyroxene (enstatite) in mantle peridotites is Al-poor (0.05-0.08 Al a.p.f.u.) and has Mg# 90.5-91.5. Orthopyroxene from peridotite cut by orthopyroxenite veins is even poorer in Al (0.03-0.04 a.pfu) and has lower Mg# 91.1-91.7 and is chemically indistinguishable from pyroxenitic orthopyroxene. Orthopyroxene forming cumulates has Mg#=82.3-84.0 and the highest Al content among all the lithologies (0.12-0.14 a.p.f.u.). Peridotitic clinopyroxene (diopside) has Al=0.02-0.08 a.p.f.u. which corresponds well to this in orthopyroxene, but Mg# is higher – 92.5-95.4. Clinopyroxene in cumulate rocks has Al content=0.13-0.16 a.p.f.u. and Mg#=87-88. Spinel in mantle peridotites has Cr#=0.47-0.80 and is negatively correlated with Mg# (0.38 to 0.56). The cumulative spinel has lower Cr# (0.18-0.27), but the  Mg# is similar to that forming peridotite (0.38-0.45). </p><p>The orthopyroxene equilibration temperatures calculated with Witt-Eickschen & Seck (1991, CMP) algorithm, yield wide range of temperatures (800-950˚C in mantle peridotites and 950-1020˚C in cumulate peridotites suggesting its magmatic origin). Low Al content in orthopyroxene suggest that peridotites suffered from high degree of melt extraction.</p><p>Chemical composition of minerals forming rocks of Kukesi Massif is typical  for mantle sections of SSZ ophiolites (e.g. Troodos ophiolite, Batanova & Sobolev 2000, Geology). Our preliminary mineral chemical data for Kukesi ultramafics have a wider range than those previously obtained by Morishita et al. (2011, Lithos). The chemical composition of ultramafic rocks within this massif varies, which may result from variable geochemical history, but further studies are required to fully characterize the composition of Kukesi ultramafics and to reconstruct its geochemical and tectonic evolution.</p><p>This study was financed from scientific funds for years 2018-2022 as a scientific project within program “Diamond Grant” (DI 024748).</p>

Spinel-free and spinel-poor dunite veins crosscutting the Wadi Rajmi ophiolite chromitite (northern Oman ophiolite)

2013 ◽  
Vol 184 (3) ◽  
pp. 261-266
Author(s):  
Khadidja Abbou-Kebir ◽  
Shoji Arai ◽  
Ahmed Hassan Ahmed ◽  
Georges Ceuleneer
Keyword(s):  
Mantle Source ◽  
Cooling Rates ◽  
Oman Ophiolite ◽  
Tectonic Regime ◽  
Ore Body ◽  
Depleted Mantle ◽  
History Of ◽  
Podiform Chromitite

Abstract Peculiar dunitic veins almost or totally free of spinels crosscut a podiform chromitite ore body in the Wadi Rajmi, northern Oman ophiolite. They probably originated from a komatiitic melt which was oversaturated in Fo≤94 olivines and which evolved to precipitate simultaneously both chromian spinels, with Cr# ranging from 0.6 to 0.8, and Fo91-93 olivines. The absence or the low modal amounts of spinels are possibly governed by a Cr-undersaturation state of the involved melt which crystallized under relatively low cooling rates to generate the spinel-free and the spinel-poor dunites. A shallow and highly depleted mantle source for this komatiitic melt was envisaged during a converging tectonic regime, initiated earlier in the dynamic history of the Oman ophiolite.

Low-T formation of high-Cr spinel with apparently primary chemical characteristics within podiform chromitite from Rayat, northeastern Iraq

2006 ◽  
Vol 70 (5) ◽  
pp. 499-508 ◽  
Author(s):  
S. Arai ◽  
Y. Shimizu ◽  
S. A. Ismail ◽  
A. H. Ahmed
Keyword(s):  
Chemical Properties ◽  
Chromian Spinel ◽  
Chemical Characteristics ◽  
Silicate Matrix ◽  
Mantle Origin ◽  
Ophiolitic Mélange ◽  
Magnesian Olivine ◽  
The Matrix ◽  
Detrital Particles ◽  
Podiform Chromitite

AbstractChemical modification of chromian spinel at low-T alteration was examined in detail for a podiform chromitite from a Tethyan ophiolitic mélange belt at Rayat, northeastern Iraq. The chromitite is highly brecciated and the matrix has been completely altered, producing chlorite and carbonate (dolomite and calcite). High-Cr, low-Fe3+ spinel has formed along the margins and cracks of chromian spinel grains throughout the alteration, associated with unaltered primary spinel and magnetite without ferritchromite. In associated harzburgites, only ferritchromite is found instead of the high-Cr, low-Fe3+ spinel. The high-Cr, low-Fe3+ secondary spinel apparently has chemical properties of mantle origin, plotted at the extension of ordinary mantle spinels on compositional spaces. The character is due to subtraction of Al as chlorite with the addition of an amount of magnetite component from the silicate matrix, which is small in volume relative to peridotite and composed of highly magnesian olivine (up to Fo97). We should treat high-Cr chromian spinels with caution in highly altered mantle-derived rocks, especially chromitite and other rocks with highly magnesian olivine, as well as in detrital particles for provenance study.

scholarly journals Crystal structure of Al2.95Cr0.59, a phase closely related to the η-phase in the binary Al–Cr system

IUCrData ◽  
2020 ◽  
Vol 5 (10) ◽  
Author(s):  
Xu Geng ◽  
Bin Wen ◽  
Changzeng Fan
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Chemical Composition ◽  
Structure Analysis ◽  
Monoclinic Phase ◽  
Site Occupation ◽  
Al Content ◽  
High Pressure Sintering ◽  
Close Relationship ◽  
Cr System

The monoclinic η-phase in the binary Al–Cr system was initially named by Bradley & Lu [Bradley & Lu (1937). J. Inst. Met. 60, 319–337] as having the composition Al11Cr2 (Al:Cr ratio = 5.5:1). Its crystal structure was later refined [Cao & Kuo (2008). J. Alloys Compd. 458, 30, 319–337] to have a slightly lower Al content (Al:Cr ratio = 5.16:1). In the present work, a monoclinic phase with composition Al2.95Cr0.59 (Al:Cr ratio = 5.04:1) was obtained by high-pressure sintering (HPS) of a stoichiometric Al11Cr2 mixture. Structure analysis of this phase, hereafter named η′, revealed a close relationship to the previously reported η-Al11Cr2 structure, but with different mixed-occupied sites. Five fully occupied sites exhibit refined site occupation factors of 0.899 (5), 0.984 (4), 0.977 (5), 0.946 (4) and 0.945 (4) for the corresponding Al atoms. Moreover, there are no split Al sites in the η′-structure as reported for the η-structure. The refined chemical composition of the η′-phase revealed that it comprises two Al atoms fewer and two Cr atoms more than the previously reported η-Al11Cr2 phase.

Anandite, a new barium iron silicate from Wilagedera, North Western Province, Ceylon

1967 ◽  
Vol 36 (277) ◽  
pp. 1-4 ◽  
Author(s):  
D. B. Pattiaratchi ◽  
Esko Saari ◽  
Th. G. Sahama
Keyword(s):  
Chemical Composition ◽  
Iron Ore ◽  
Iron Silicate ◽  
Space Group ◽  
Magnetite Ore ◽  
Western Province ◽  
The North ◽  
Ore Body ◽  
North Western ◽  
Simplified Formula

SummaryAnandite is a new barium iron silicate found in the magnetite ore zone of the Wilagedera iron ore body, in the North Western Province of Ceylon. The mineral is named after the late Dr. Ananda Coomaraswamy, the first director of the Mineral Survey of Ceylon.Anandite is monoclinic, with a 5·412, b 9·434, c 19·953 Å, β 94° 52′, space group C2/c. D 3·94, hardness 3–4. Optically positive, b ‖ β, γ ∧ a 12°, β 1·855, γ > 1·88. Pleochroism: β green, γ brown. Chemical composition corresponds to the simplified formula (Ba,K) (Fe,Mg)a (Si,Al,Fe)4O10 (O,OH)2 with Z = 2. The data available indicate that the mineral has the trioctahedral structure of the brittle micas.

Kinetics of palygorskite hydrolysis in dilute salt solutions

Clay Minerals ◽  
2000 ◽  
Vol 35 (2) ◽  
pp. 433-441 ◽  
Author(s):  
A. Neaman ◽  
A. Singer
Keyword(s):  
Chemical Composition ◽  
Chemical Compositions ◽  
Salt Solutions ◽  
Initial Amount ◽  
Al Content ◽  
Surface Areas ◽  
Soils And Sediments ◽  
High Al Content ◽  
Neutral Conditions ◽  
Kinetics Of

AbstractFive palygorskite samples with different chemical compositions and specific surface areas (SSA) were used for this study. Batch experiments in dilute salt solutions under neutral conditions were conducted to study the kinetics of clay hydrolysis. The rates of release of Mg and Si differ significantly among the palygorskite samples. It was found that differences in release rate of Mg among the palygorskite samples are due to differences in both surface area and chemical composition. The rate of release of Mg was greater in palygorskites with high SSA and high Mg and Fe contents than that in palygorskites with low SSA and high Al content. The rate of release of Si depends on the SSA of the mineral and is not related to chemical composition. The initial amount of Si released increases with SSA, while the Si rate of release decreases with increasing SSA. These data suggest that the decomposition of palygorskite in soils and sediments also takes place under neutral conditions.

Modeling the Kinetics of Saline Minerals Dissolution in Dombrovsky Quarry at the Kalush-Golinsky Potassium Salts Deposit

2020 ◽  
Vol 42 (4) ◽  
pp. 60-68
Author(s):  
Ya.O. MALKOVA ◽  
V.M. BOBKOV ◽  
V.V. DOLIN
Keyword(s):  
Chemical Composition ◽  
Diffusion Process ◽  
Atmospheric Precipitation ◽  
Point Of View ◽  
Concentration Difference ◽  
Hydrated Ions ◽  
Ore Body ◽  
Composition Formation ◽  
Host Rocks ◽  
Concentration Diffusion

The article deals with the peculiarities of the chemical composition formation of brines in the Dombrovsky quarry, primarily due to the dissolution of potash ore minerals and host rocks in water coming from the pebble horizon and atmospheric precipitation. The solubility of the ore body minerals has been studied, and it ranges from 333 to 502 g∙dm–3. The boundary conditions for the formation of a saturated salt solution were determined. The estimated concentration of saturated potash ore solution under normal conditions is 426 g∙dm–3. The mechanism of dissolution is considered from the standpoint of D.I. Mendeleev's chemical theory of solutions. The temporary dynamics of minerals dissolution of the ore body is studied experimentally. The parameters of kinetic-diffusion process are calculated. The rate of the dissolution process, which occurs in the kinetic region, significantly exceeds the rate of concentration diffusion of hydrated ions: from 5 to 400 times depending on the mineral composition of salts. Theoretically from the point of view of multistage process kinetics and experimentally in laboratory conditions it is proved that the process that determines the formation of the chemical composition of brines (the slowest stage) is the concentration diffusion of hydrated ions Na+, K+, Cl–. They enter the liquid phase due to the minerals dissolution of the ore body and host rocks of soil and sides of the quarry, in the direction of overcoming the concentration difference - from the lower layers of the brine to its surface. This conclusion is confirmed by the ratio of weight coefficients а1 and а2. The contribution of the process of the main minerals dissolution of the ore body to the chemical composition formation of the solution is significantly less than the concentration diffusion process.

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