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Plutonic Rocks of Myanmar

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WEST YANGON UNIVERSITY
Department of Geology
PLUTONIC ROCKS OF MYANMAR
Project Paper
by
Maung Tun Tun Naing
3 Geol (Hons)- 4
March, 2019
INTRODUCTION
PLUTONIC ROCKS OF MYANMAR
ECONOMIC MINERALS AND OLD DEPOSITS
CONCLUSION
Forms and Structure of Plutonic Rocks
 Igneous Rocks
Intrusive (Plutonic)
Extrusive (Volcanic)
 Volcanic Rocks- solidification of lava at earth surface.
 Plutonic Rocks- magma solidified within the crust or
mentle.
 Plutonic Rocks
Concordant Structure
Discordant Structure
Concordant Structures
 Parallel to the bedding plane.
 don’t disturb the individual layers of country rocks.
 Laccoliths
 Lapoliths
 Sills
Discordant Structures
 Perpendicular to the bedding plane.
 Cut across the bedding layers of country rocks.
 Dyke (dike)
 Batholith
 Stock
Figure showing the plutonic structures of igneous rocks
QAPF Classification for Plutonic Rocks
 The actual properties of the various minerals.
 Q- Quartz.
 Alkali feldspars- orthoclase, microcline, perthite, anorthoclase, and albite.
 P- Plagioclase, Scapolite.
 F- Feldspathoids or foids- leucite, nepheline,
sodalite, analcite, etc.
Rocks with Mafic minerals
less than 90% (M<90)
Rocks with Mafic minerals greater than 90% (M>90%)
 The rock is Ultramafic.
 Classified according to their content of mafic minerals.
 Olivine, orthopyroxene, clinopyroxene, hornblende.
A Breif account of Plutonic Activities in Myanmar
 Eastern granitoid Belt (Triassic)
 Western Granitoid Belt (Mesozoic to Paleocene)
 Central Igneous Belt (Late Cretaceous to Pleistocene)
 Serpentinite Belt (Late Cretaceous to Eocene)
Time
Area and Occurrences
Rock Types & Associated
Mineral Deposits
End of Early Carboniferous
Taung Baing, W of Bawdwin.
Biotite granite.
Triassic
Eastern granitoid belt.
Batholiths of biotite granite.
Mesozoic & Paleocene
(mainly late Jurassic to
Paleocene)
Western Granitoid Belt. Along
Tanintharyi and western
marginal zone of Shan Plateau
Pluton of biotite granite.
Dioritic rocks (diorite,
microdiorite, quartz- diorite).
Late Cretaceous to Eocene
Serpentinite belt. Along
eastern flanks of Western
Range.
Peridotite, dunite, and
pyroxenite, mostly
transformed into serpentinite.
Late Cretaceous to Eocene
Wuntho Igneous mass.
Plutons of granite and
granodiorites.
Miocene
N-part of Western Granitoid
Belt in Kabaing,
Mogok,Kyatpyin and
Payangazu areas.
Small plutons of BiotiteGranite at Kabaing. Syenites
and alaskitic rocks in Mogok
and Kyatpyin areas.
Late Miocene
East of Pyay and Zigon.
Dolerites dykes at east of Pyay
and Zigon.
Late Pleistocene
Singu lava field, Kabwet area.
Olivine dolerite dykes and
sills.
Precambrian Age
Mogok Area
Alaskite suite
 Alaskites- sheet like intrusion.
 Alaskite Suite- Syenite, Nepheline Syenite, Tourmaline Granite,
Hornblende Granite.
 Corundum (Ruby, Sapphire), Spinel.
 Accessory minerals- Fluorite, ilmenite, topaz, tourmaline, zirconium.
Mogok Area
Kabaing Granite
 Mafic, ultramafic rocks, Pegmatites, Aplites.
 Mafic (Dolerite)
 Ultramafic (Hornblende Pyroxenite, Pyroxenite, Peridotite)
 Accessory as tourmaline are presented in Pegmatite and apatite.
 Age- Tertiary.
Carboniferous Age
Tawng Peng Granite- NSS
 One of the largest instrusive bodies in E-Kachin/ Shan State.
 Well-exposed on the cart road between Mogok- Mong Long.
 Coarse-grained Granite, Tourmaline granite.
 Accessory minerals- fibrolite, aptite, garnet.
Mesozoic and Cenozoic Plutonic rocks
Plutonic rocks in the Arakan Coastal Area and in the Western Part of
If Indo-Burman Ranges
 Intermediate to basic dykes, sills, stocks of Serpentinite.
 Serpentinite (Peridotites, Saxonites, and Pure Dunites).
 Diameter of occurrences- a few tens to rarely exceeded 100m.
 Ophiolite rocks are concordantly interbedded in Upper Cretaceous
volcanic rocks.
Plutonic rocks in the eastern parts of the Indo-Burman Ranges
 Approximately 1200 km long chain of basic to ultrabasic plutonic rock
along the structural contact between Indo- Burman and Inner Burman
Tertiary Basin.
 W- Pyay- W- Minbu- Serpentinite masses are observed along the fault
contact between Cretaceous Flysch sequences in the W and Eocene
sediments in the E.
 An approximately 100km long and up to about 15 km wide chain of
Ultrabasite- Along the main fault zone W- Kalemyo.
 Serpentinite, Gabbro, Diorite, Peridotite.
 Accessory minerals- Chromite, Magnetite.
 Chalcedony, quartz, chrysolite, magnetite, chlorite, talc, Nickel
(Joints and crevice in the ultrabasites).
 Further ultrabasites at W edge of the N Chindwin Basin and from the
S border of the Hukawng Basin.
Plutonic rocks along the Inner Volcanic Arc
 Characterized by a discontinuous chain of basic, intermediate, acid,
Cretaceous and Tertiary to sub- recent intrusive.
 N-Mt. Popa- Basic and Intermediate intrusive occur in more or less
parallel zones.
 SW- Kyaukpyu (Tharrawaddy District)
5 occurrences.
 Olivine- dolerite, largely serpentinized, in baked Miocene mudstone.
 E- Aunglan, Pyay District)
3 occurrences.
 Olivine- dolerite, dolerite sills, highly serpentinized, in baked
Miocene mudstone.
Ultrabasic
(a) Peridotites- Twindaung
(b) Perknites- Twindaung
Basic- Intermediate
(a) Augite- diorite- Salingyi
(b) Diorite- Salingyi
(c) Quartz- diorite- Twindaung
Geological Map of Lower Chindwin Area.
Shwetaung Formation (E and central parts of N- Wuntho Massif)
 Recent andesite, dacite dykes, biotite granodiorite, quartz diorite and
granite.
 Age- Early Upper Cretaceous Age.
Plutonic Rocks along Shan Boundary Fault System
 E of the Sittaung Estuary to the N as far as the NE of Pyinmana.
 Fined- grained Soda- granite, medium- grained Potash granite,
Aplite, Dolerite and Hornblende- granophyre dykes with pyrite and
hematite.
 Age- Upper Cretaceous to Lower Eocene.
 W of Neyaungga and Ye-ngan.
 NS trending batholith masses of Granodiorite, Adamellite, Biotite
granite with Microgranite dykes, Aplite, and wolframite bearing
Pegmatite.
 Age- Upper Cretaceous to Lower Tertiary.
Plutonic Rocks in the Sino- Burman Ranges
 Three belts in the Tenesserim, Mergui, and Tavoy Districts
 Run parallel to each other at about 20 to 50 km in the same direction,
follow the general strike of the Paleozoic sediments.
 Acid and basic Pegmatite, Tourmaline- Pegmatite, Quartz dykes,
Biotite granite, Hornblende granite, Tourmaline- muscovite granite.
 Age- Upper Triassic- Lower Triassic, Upper Cretaceous.
ECONOMIC MINERAL AND ORE ASSOCIATION
Tin- Tungsten bearing Granites
 Associated with the intrusion of a series of granite belts that run
broadly NS for 100 km in SEA.
Near the outer margins of granite intrusions.
 Mode of occurrences
Segregation in granites and in quartz veins.
Adjoining sedimentary rocks.
 Myanmar Tin production- focused on a belt along the Myeik,
especially around the town of Dawei (Tavoy)
Chromite Deposits
 Widespreadly occur in Myanmar being related to NS trending
ophiolite lines.
 Hinthada, Mindon Thayetmyo, Ngape, Mindat- Kanpetlet, Saw and
Mwetaung- Kalemyo.
 Mwetaung- in Dunite layers of the Ophiolite sequence.
 40 occurrences.
 Massive type with few nodular.
 Tagaung Taung- concentrated in the periphery of the dunite layers
having a thickness of 150m.
 44 occurrences.
 Massive type- high chromium oxide content.
Nickel Deposit
 Two important nickel laterite deposits, one at Mwetaung- Chin Hills
and another one at Tagaung Taung.
 Formed by differential weathering of ultramafic rocks under tropical
condition.
CONCLUSIONS
Thank you…