TY - JOUR

T1 - Texture and composition of ferrian ilmenite from hornblende andesites of the timok magmatic complex, Serbia

AU - Luković, Aleksandar

AU - Vulić, Predrag

AU - Zavašnik, Janez

AU - Cvetković, Vladica

AU - Šarić, Kristina

AU - Banješević, Miodrag

AU - Lazarov, Marina

AU - Pačevski, Aleksandar

N1 - Funding Information: This study was supported by the project OI_176016 of the Ministry of Education, Science and Technological Development of the Republic of Serbia and by the bilateral project between Serbia and Slovenia: “Micro-to nanoscale textures of ore minerals: methods of study and significance”, BI-RS/18-19-035. We are thankful to the Zijin, Rakita and Tilva companies for the permit to use samples and data from the Nikoličevo licence area in this study, and to Dr. Danica Bajuk-Bogdanović for obtaining the micro-Raman spectroscopy results. The authors are also grateful to two anonymous reviewers and Associate Editor Dr. Ivan Savov for helpful comments and suggestions which considerably improved the manuscript.

PY - 2021/1/29

Y1 - 2021/1/29

N2 - Ferrian ilmenite, representing an intermediate member of the hematite-ilmenite solid solution, is frequently present as an accessory mineral in hornblende andesites of the Timok Magmatic Complex (Serbia), which host world-class porphyry copper systems of the Bor Metallogenic Zone. In Krivelj, a type locality of this rock, ferrian ilmenite occurs in homogenous crystals without exsolutions present. Its unit cell parameters are a = 5.062(1) Å, c = 13.895(4) Å, V = 308.4(1) Å3 and according to the dependence of unit volume with composition, studied ferrian ilmenite corresponds to an intermediate member of the series with 53 mole% ilmenite (Xilm = 0.53). Transmission electron microscopy investigations show that this mineral is homogenous in terms of hematite-ilmenite solid solution and presence of exsolutions, even at the nanoscale level. Ferrian ilmenite from other localities (Majdanpek and Nikoličevo) shows various patterns of exsolution texture. Thus, ferrian ilmenite from Majdanpek shows very fine exsolutions of hematite-ilmenite phases. X-ray diffraction analysis confirms that initial ferrian ilmenite is broken down to two phases: a predominant host phase (ilmenohematite) with Xilm = 0.31 and a second exsolved phase (hemoilmenite) with Xilm = 0.78. Average grain compositions of this decomposed ferrian ilmenite correspond to a large degree to the previous homogenous ferrian ilmenite from Krivelj. However, due to slower cooling of andesite from the Majdanpek locality, a subsequent breakdown of the initial ferrian ilmenite was played out resulting in the formation of exsolution textures, that also caused changes in the magnetic properties of this mineral. In general, differences in ferrian ilmenite textures can imply the local variability in the conditions of the formation of the host volcanic rock and/or indicate that subsequent alteration processes have occurred.

AB - Ferrian ilmenite, representing an intermediate member of the hematite-ilmenite solid solution, is frequently present as an accessory mineral in hornblende andesites of the Timok Magmatic Complex (Serbia), which host world-class porphyry copper systems of the Bor Metallogenic Zone. In Krivelj, a type locality of this rock, ferrian ilmenite occurs in homogenous crystals without exsolutions present. Its unit cell parameters are a = 5.062(1) Å, c = 13.895(4) Å, V = 308.4(1) Å3 and according to the dependence of unit volume with composition, studied ferrian ilmenite corresponds to an intermediate member of the series with 53 mole% ilmenite (Xilm = 0.53). Transmission electron microscopy investigations show that this mineral is homogenous in terms of hematite-ilmenite solid solution and presence of exsolutions, even at the nanoscale level. Ferrian ilmenite from other localities (Majdanpek and Nikoličevo) shows various patterns of exsolution texture. Thus, ferrian ilmenite from Majdanpek shows very fine exsolutions of hematite-ilmenite phases. X-ray diffraction analysis confirms that initial ferrian ilmenite is broken down to two phases: a predominant host phase (ilmenohematite) with Xilm = 0.31 and a second exsolved phase (hemoilmenite) with Xilm = 0.78. Average grain compositions of this decomposed ferrian ilmenite correspond to a large degree to the previous homogenous ferrian ilmenite from Krivelj. However, due to slower cooling of andesite from the Majdanpek locality, a subsequent breakdown of the initial ferrian ilmenite was played out resulting in the formation of exsolution textures, that also caused changes in the magnetic properties of this mineral. In general, differences in ferrian ilmenite textures can imply the local variability in the conditions of the formation of the host volcanic rock and/or indicate that subsequent alteration processes have occurred.

KW - Andesite

KW - Exsolutions

KW - Hematite

KW - Hemoilmenite

KW - Ilmenite

KW - Ilmenohematite

KW - Nikoličevo

KW - Porphyry copper

KW - Solid solution

KW - Texture

KW - Timocite, Krivelj

UR - http://www.scopus.com/inward/record.url?scp=85100680709&partnerID=8YFLogxK

U2 - 10.1127/njma/2021/0240

DO - 10.1127/njma/2021/0240

M3 - Article

AN - SCOPUS:85100680709

VL - 197

SP - 65

EP - 83

JO - Neues Jahrbuch fur Mineralogie, Abhandlungen

JF - Neues Jahrbuch fur Mineralogie, Abhandlungen

SN - 0077-7757

IS - 1

ER -