**3. Field observations**

In field photos, numerous lithological rock-suits with field relationships are drawn and the genuine petrological research is performed. The detailed physiochemical features of various hills are defined as:

### **3.1 Extrusive phase**

#### *3.1.1 Basalt*

The basalt flow occurs predominantly in the inner parts of the NRC hills of Sewadiya, Maini and Dadawari. Basalt has a fine grained and colour is black/dark brown, light greyish brown, and dark greyish brown. Basalt forms with a maximum thickness of 10 m and the rhyolite and trachyte flows are underlying. The flows of rhyolite and basalt display radial pattern (**Figure 2A**) and sharp contact with themselves (**Figure 2B**). The basalt contains large vesicles (4–6 mm) and often calcite fills the vesicles. Basalt xenoliths in the rhyolite (**Figure 2C**) and trachyte are found to suggest that basalt is older than rhyolite and trachyte.

#### *3.1.2 Trachyte*

At the outer margin of each hill, the trachyte flow is observed and it is the second dominant form of rock after the rhyolite. Trachyte flows of porphyritic as well as nonporphyritic nature are dark/light bluish color. It occurs on Milara hill at a maximum thickness of 50 m. Sharp contact is observed between trachytes and rhyolites. Basalt xenoliths in trachytes suggest that the flows of trachyte are younger than basalt.

#### *3.1.3 Rhyolite*

Rhyolite occurs in almost all the hills in NRC with the pyroclastic assemblages and is the most prevalent rock form in NRC. The color of rhyolite is primarily dark brown (**Figure 3A**) with different hues of light brown, red brick, grey, green, black, blue and purple. It is considered in nature to be porphyritic and non-porphyritic. In *Petrology and Geochemistry of Nakora Ring Complex with Emphasis on Tectonics… DOI: http://dx.doi.org/10.5772/intechopen.98609*

**Figure 2.**

*(A) Radial pattern present in Sewadiya hill, (B) basalt underlies the dark color rhuolite, (C) xenolith of basalt present in the rhyolite, (D) spherical weathering of the rhyolite rock.*

the Nakora area, the maximum flow thickness is 200 m, represented by dark brown rhyolite at Sewadiya and Maini hill.

On the Northeastern flank of Sewadiya hill, spheroidal rhyolite is exposed. It is light yellow to pale brown in color. In a region of 200 sq. meters, the spheroidal rhyolite is exposed. The spheroidal structure is up to 5 m in size and shows a large number (up to 65) of few cm thick concentric shells surrounding a nuclei (**Figure 2D**). The shells consist of concentric layers of light and dark colors. They occur mostly in circular/semicircular and square shapes as well. A sharp contact is observed between the spheroidal rhyolite and the brown rhyolite.

#### **3.2 Pyroclastic assemblages**

There are exposures of ash, welded tuff, blast breccia, agglomerate and perlite. In the inner part of Sewadiya hill, there is a small bed of volcanic ash (light yellow color). Tuff demonstrates different colors, viz. Light yellow to light grey, but glassy material and tiny vesicles are also noted in it in a few areas. Sharp contact with basalt (**Figure 3B**) and rhyolite is indicated by Tuff. In the foothills of the Maini hill, angular fragments of explosive breccia and agglomerate (rounded to elongate in form with a diameter of 6–10 cm) are observed.

#### **3.3 Intrusive phase**

#### *3.3.1 Granite*

Granite is primarily exposed at three NRC sites, i.e. the inner parts of Sewadiya, Maini, and Dadawari hill. The granites display varying shades of pink, dark pink

**Figure 3.**

*(A) flow bands in non-porphyritic rhyolite, (B) contact between tuff and basalt, (C) contact between rhyolite and granite, (D) dolerite dyke.*

and light pink, respectively. They are medium, large and compact grains. In the study zone, sharp contact of granite with rhyolite is observed. The intrusive aspect of granite in the rhyolite promotes volcanic plutonic association and sub-volcanic nature (**Figure 3C**).
