| Abstract | Na području magmatsko-metamorfnog kompleksa Motajice, planinskog masiva na sjeveru Bosne i
Hercegovine sakupljeno je i analizirano 17 uzoraka granita. Utvrđeno je da se graniti razlikuju po svome
mineralnom sastavu, teksturi i strukturi prema čemu se mogu svrstati u četiri tipa granita: biotitni granit,
dvotinjčasti granit, leukokratni granit i grajzen. Biotitni granit čine kvarc, ortoklas i biotit, a struktura mu je
zrnata do porfiroidna. Dvotinjčasti se sastoji od kvarca, ortoklasa, mikroklina, muskovita, biotita te klorita,
sericita i limonita, a zrnate je alotriomorfne strukture, ponekad kataklastične. U mineralnom sastavu
leukokratnog granita glavni su kvarc, ortoklas, mikroklin i muskovit, a akcesorni su cirkon, titanit, monacit te
sekundarni minerali klorit i sericit. Prisutna je i limonitizacija. Struktura je zrnata alotriomorfna, ponekad
kataklastična. Grajzen je zrnate alotriomorfne strukture, a u mineralnom sastavu glavni su kvarc i muskovit sa
cirkonom, titanitom i monacitom i sekundarnim sericitom i limonitom. Dvotinjčasti i leukokratni granit su
većinom neizmijenjeni, dok su grajzen i biotitni granit pretrpjeli alteracije kao što su grajzenizacija,
sericitizacija, limonitizacija.
Na temelju mineralnog sastava, struktura i tekstura samih granita, utvrđen je slijed kristalizacije različitih
tipova granita. Cirkon kristalizira pri najvišim temperaturama (uklopak u biotitu), a odmah iza njega slijedi
biotit. Nakon biotita kristaliziraju feldspati, muskovit, titanit, monacit i kvarc, a klorit i sericit kristaliziraju pri
najnižim temperaturama kao produkti alteracija. Limonitizacija se odvija pri površinskim temperaturama. U
svim tipovima granita pojavljuju se isti akcesorni minerali kao što su cirkon, titanit i monacit, što upućuje na
postanak iz istog tipa magme. Najranije kristalizira biotitni granit, slijede ga dvotinjčasti pa leukokratni granit.
Padom temperature odvijaju se pneumatolitske (grajzenizacija), hidrotermalne (sericitizacija i kaolinitizacija)
i površinske izmjene (limonitizacija) u granitnom kompleksu. Lokacije na kojima se nalaze graniti podvrgnuti
sericitizaciji i grajzenizaciji (manje od 1% granitnog kompleksa) su povoljne za nastanak orudnjenja skarnskog
i hidrotermalnog tipa gdje bi se trebala obavljati daljnja istraživanja. |
| Abstract (english) | In the area of Motajica, an igneous-metamorphic mountain complex, in the north Bosnia and Herzegovina, 17
samples of granite were collected and analyzed. The samples were then categorized into 4 types of granites
according to their mineral composition, texture and structure: biotite granite, two-mica granite, leucocratic
granite and greisen. The biotite granite consists of quartz, orthoclase and biotite and its texture is granular to
porphyroid. The two-mica granite is made of quartz, orthoclase, microcline, muscovite, biotite, chlorite, sericite
and limonite and the texture is granular allotriomorphic, sometimes cataclastic and myrmecite. The mineral
composition of leucocratic granite is quartz, microcline, muscovite and the accessory minerals are zircon,
titanite, monazite. The secondary minerals are sericite and limonite and limonitization is also present. The
texture is granular allotriomorphic, sometimes cataclastic. Greisen has granular allotriomorphic texture. It is
made of quartz and muscovite along with accessory zircon, titanite and monazite and secondary sericite and
limonite. Two-mica and leucocratic granites are mostly fresh, while greisen and biotite granite have suffered
alterations such as greisenization, sericitization and limonitization.
Based on the mineral composition, structure and texture of the granites, the sequence of crystallization of
different types of granites was determined. Zircon crystallizes at the highest temperatures (as an inclusion in
biotite). After biotite feldspars, muscovite, titanite, monazite and quartz crystallized, and chlorite and sericite
crystallized at the lowest temperatures as the products of the alterations. Limonitization takes place at the
temperatures which are present on the surface. Accessory minerals, zircon, titanite and monazite, are the same
in all types of granite suggesting the formation from the same magma type. The first one which crystallizes is
the granite with frozen-edges followed by normal granite and then leucocratic granite. As the temperature
drops, pneumatolytic (greisenization), hydrothermal (sericitization and kaolinitization) and surface
(limonitization) alterations occur in the granite complex. Locations where the granites are subjected to
sericitization and greisenization (which is less than 1% of the granite complex) are favorable for the occurrence
of skarn and hydrothermal types of mineralization and further researches should be performed there. |
