This document characterizes and describes the granite found near Dharoi, Taranga Hill in Mahesana District, Gujarat, India. Two variants of the Sendra-Ambaji granites were observed - a plagioclase-rich porphyritic granite and a K-feldspar rich porphyritic granite. Alteration of the granite was also seen through albitization and silicification. Skarn deposits and zones were identified where the granite intruded carbonate country rocks. The granite intrusion and associated hydrothermal activity resulted in the formation of veins, joints, and replacement zones in the country rocks.

1. CHARACTERISATION OF GRANITE ON THE BASIS OF FIELD RELATION IN AND
AROUND DHAROI, TARANGA HILL, MAHESANA DISTRICT,Gujarat; india
BY
DARSHAN DARJI
AKASH LIMBACHIYA
UNDER THE GUIDANCE OF
MS. MADHUMAYEE MOHANTA
MS.NAYANI DAS
GEOLOGIST, GEOLOGICAL SURVEY OF INDIA
M.G. Science Institute
(Geology Department)
Navrangpura,Ahmedabad,Gujarat 380009
darshandaiya234@gmail.com

2. CONTENT
 Objective
 Location and accessibility
 Physiography
 Geology of the study area
 Lithostratigraphy of the study area.
 Conclusion
 References

3. OBJECTIVE
 Characterization of granite in and around Dharoi, Taranga hill,
mahesana District, Gujarat.

4. LOCATION AND ACCESSIBILITY
Toposheet no. 45D/16 OR 46A/13 of Mahesana District of Gujarat
Study Area΄s

5. GOOGLE EARTH IMAGE OF STUDY AREA΄s
Study Area΄s
Source : Google earth image

6. PHYSIOGRAPHY
Symbol layer name legend VELYU
Physiography of study area
Source : BHUKOSH, GSI

7. GEOLOGY OF THE STUDY AREA
Table source : Ahmad, T. and Tarney, J., 1994.
Paleo to
Mesoproterozoic

8. Taranga Hill

9. LITHOSTRATIGRAPHY OF THE STUDY AREA
Aeolian sand/Soil cover
Quartz vein
Pegmatite vein
Microgranite/Microgranite dyke
K-feldspar rich porphyritic granite
Plagioclase rich porphyritic granite
Microgranite
Calc silicate Gneiss (Delhi Super group) Not exposed in study area
Sendra-Ambaji granite

10. SENDRA - AMBAJI GRANITE intrusion
 Two variants of Sendra Ambaji granitoids :
 Plagioclase rich porphyritic granite
 K-feldspar rich porphyritic granite
 Medium to coarse grained.
 Grey to white/pinkish in colour .
 Composed of quartz, orthoclase, plagioclase, biotite and amphibole.
 Feldspar phenocryst size : 1-5 cm

11. Plagioclase rich porphyritic granite near
Taranga road section
Feldspar phenocryst 3.5 cm size in
porphyritic granite

12. K-feldspar rich porphyritic granite near Dharoi Dam

13. Microgranite rock found north of maneknath temple

14. Pegmatite veins
Pegmatite vein in Micro Granite rock near vekari
village
Pegmatite
vein

15. Igneous Intrusion
Terrain
Metamorphic Terrain
CA - SI VEIN
Smokey Quartz

16. ALTERATION
 The hydrothermal alteration of the granite proceed mainly by dissolution-
Precipitation process resulting from the infiltration of hydrothermal fluid along the
microcracks.
 Alteration of rock in which plagioclase is albitized freeing the anorthite molecule
for the formation of epidote.

17. Fluorite vein in
granitic rock
Silicification in
granitic rock

18. JOINTS & STRUCTURE
2 set joints Trending
280,255 Respectively

19. Mafic microgranular enclaves (MME) are
commonly found in granodiorites and
monzogranites and have sharp contacts with
the host rocks. Sometimes, the fine veins of
the host rocks cut through the enclaves.
Tafoni weathering
Known as honeycomb weathering or
"Swiss-cheese rock," Tafoni (singular:
tafone) are small, rounded, smooth-edged
openings in a rock surface, most often
found in arid or semi-arid desert

20. SKARN DEPOSITS
 Skarn deposits are developed due to replacement, alteration, and contact
metasomatism of the surrounding country rocks by ore-bearing hydrothermal
solution adjacent to a mafic, ultramafic, felsic, or granitic intrusive body. They
most often develop at the contact of intrusive plutons and carbonate country rocks.
 Skarn deposits are one of the more abundant ore types in the earth's crust and
form in rocks of almost all ages. Skarn is a relatively simple rock type defined by
a mineralogy usually dominated by calcsilicate minerals such as garnet and
pyroxene.
 In near Dharoi region we found skarn deposits replacement, alteration, and contact
metasomatism of the surrounding country rocks by ore-bearing hydrothermal
solution adjacent to a mafic, ultramafic, felsic, or granitic intrusive body. We
Epidote, Diopside, Fluorite, Garnet Bearing Granite Rock.

21. Fluorite Diopside Epidote

22. Conclusion
 In the context of present study, toposheet no. 45D/16and 46A/13 an area of
Dharoi, Taranga hill area of mahesana District northern Gujarat.
 The major lithounits observed are K- feldspar rich granite and plagioclase rich
granite, deformed quartzofeldspathic veins, graphic granite veins and reef and
pegmatites, intruded by quartz veins.
 This porphyritic, undeformed granite is the youngest granitic phase of Sendra-
Ambaji suite.
 Such occurrences of wollastonite + andalusite + tourmaline within argillaceous
calc gneiss demarcate the skarn zone, likely formed by replacing impure
carbonate rock or dolomite adjacent to granitic intrusive, probably at shallow
crustal depth with the advent of post magmatic ascending hydrothermal solutions
involving “infiltration metasomatism”.

23. Continue…
 Porphyritic granite is relatively enriched in total REE (∑ REE) concentration
compared to granite and gneiss showing similar REE pattern which suggests their
similar magmatic evolution. The trace elements and REE distribution patterns of
granite gneiss and porphyritic granite show positive (+ ve) Th, Rb, K and La
anomaly and negative (-ve) Ba, Nb, Sr and Ti anomaly, indicating subduction
zone granitic magmatism
 Thus it is apparent that the time span between the tectono-thermal events
associated with the emplacement of the Sendra-Ambaji Granites at ~ 960 – 850
Ma.

24. references
 Geology and mineral resources of Gujarat ,Daman and Diu published by GSI No.30 part 14
2012, pp. 11
 Geochemistry and petrogenesis of late Archaean Aravalli volcanics, basement enclaves and
granitoids, Rajasthan. Precambrian Research.
 Arindam Dutta, Shukla Dutta and Gagan Chandra Barik, Geologists, SPECIALISED
THEMATIC MAPPING OF THE DELHI SUPERGROUP OF ROCKS IN DANTA-BHANPUR
AREA OF BANASKANTHA DISTRICT OF GUJARAT (Final Report for Field Season 2012-
14)
 Gupta, S.N., Mathur, R.K. and Arora, Y.K., 1992. Lithostratigraphy of Proterozoic rocks of
Rajasthan and Gujarat - a review. Rec. Geol. Surv. India, v , pp. 63-85
 https://www.sciencedirect.com/(SKARN DEPOSITS)
 https://www.nps.gov/(Tafoni weathering)
 https://onlinelibrary.wiley.com/(Mafic microgranular enclaves)