The main Tosham hill is an
extinct volcano which erupted sometime 732
Ma BP (million years before present).
Geologic province of Khanak-Tosham-Dharan-Riwasa-Nigana Khurd-Dulheri-Kharkari Makhwan-Dadam-Khanak is a narrow oval shaped
ring dike of eroded extinct volcanoes on the periphery of a collapsed
caldera (
magmatic chamber) of roughly diameter on its longest Khanak to Nigana Khurd NW-SE axis and on its narrower Dadam to Tosham E-W axis. This sub-surface ring dyke is now buried under the later era soils. Much of the area to the west of ring dyke is covered with
Aeolian sand flown from the fringes of
Thar Desert. The remaining area is covered under
sedimentary
alluvium soil of
Harka river of Ghaggar-Hakra River system (paleo
Sarasvati River) to the north and east, and paleo channel of
Yamuna through Bhiwani in the south and east. Among these hills, Khanak hill is the largest and tallest, and Tosham hill is the second largest smaller hill. The other neighbouring hills, in the order of decreasing size, such as Nigana Khurd, Riwasa, Dulehri, Dharan, Dadam etc. are composed of
granite porphyries.
Tosham Igneous Complex Tosham Igneous Complex has 3 main hills (Khanak, Tosham and Riwasa) and several other smaller rocky outcrops, mainly around the ring dyke: •
Tosham Hill: The main Tusham hill is the second largest hill in the range. It has
ancient rock inscriptions and
rock paintings,
paleo eroded rocky
glacial channels and water cascades, and small hilltop lakes. It consists of a
quartz porphyry ring dyke,
felsite,
welded tuff and
muscovite biotite granite. The
country rocks (
Archean Bhilwara basement rocks) native to the area are
quartzite with
chiastolite belonging to the
Delhi Supergroup. The Tosham Sn-W-Cu rocks are the source of primary
tin as well as
Tungsten and
copper, but found to be not viable commercially. The granites and
granite porphyries are high heat producing type.
Spectroscopy studies indicate that they have high abundance of
potassium (K),
uranium (U), and
thorium (Th), a sign of
radioactivity. Highest heat flow in India is recorded from this area. Commercial scale mining for stones used for construction is done in the government auctioned mines at Tosham, Khanak and Dadam hills, with several stone crushers in the zone.
Sacred sulphur ponds of Tosham Hill There are several holy ponds on Tosham Hill inside the caves, namely Pandu Teerth Kund, Surya Kund, Kukkar Kund, Gyarasia/Vyas Kund and a reservoir or a small tank on the summit of the hill to store rain water. Water in these kunds (ponds) in various caverns contain
sulfur which is considered sacred by the devotees and pilgrimages as it heals skin diseases.
Pandu Tirath, Tosham There are several sacred kunds or reservoirs on the hill; one of them, the
Pandu Tirath, is considered so sacred that some of the neighbouring villages deposit the ashes of their dead in it instead of taking them to the Ganges.
Surya Kund, Tosham The
Surya Kund is one of many kunds (pond) found in caverns of Tosham hill. It is considered sacred.
Kukkar Kund, Tosham The
Kukkar Kund is one of many kunds (pond) found in caverns of Tosham hill. It is considered sacred.
Gyarasia Kund, Tosham The
Gyarasia Kund (Vyas Kund) is one of many kunds (pond) found in caverns of Tosham hill. It is considered sacred.
Scientific studies From 1894-96,
Lt-General C.A. Mcmahon (1830-1904), who was also the president of British
Geologists' Association, was the first modern geologist to study these rocks. He described the
petrography of the rocks in 1884 and 1886 and published his work in the
Records of Geological Survey of India. During 2014-2016, Ravindra Singh and Dheerendra Singh of
Banaras Hindu University undertook first ever Indus Valley Civilization archaeological excavations of the area to confirm the connection of ores mined from these hills with the smelting metallurgical work of IVS.
Malani Supercontinent The plume related Malani magmatism in the NW Indian shield is intraplate, anorogenic, A-type and is indicative of extensional tectonic environment in the region. There is a relationship between mantle plume related anorogenic magmatism and assembly of a supercontinent. In this research paper similarities between TAB of NW Indian shield, Seychelles, Madagascar, Nubian-Arabian shield central Iran and South China constituting Malani supercontinent in terms of bimodal anorogenic magmatism, ring structures, Strutian glaciation and subsequent desiccation are discussed. Paleomagnetic data also support the existence of Malani Supercontinent The TAB is unique in the geological evolution of the Indian shield as it marks a major period of anorogenic (A-type), ‘Within Plate’, high heat producing (HHP) magmatism represented by the Malani igneous suite of rocks (MIS). The Neoproterozoic Malani igneous suite (55,000 km2; 732 Ma) comprising peralkaline (Siwana), metaluminous to milidly peralkaline (Jalor), and peraluminous (Tusham and Jhunjhunu) granites with cogenetic carapace of acid volcanics (welded tuff, trachyte, rhyolite, explosion breccia and perlite) are characterized by volcano-plutonic ring structures and radial dykes. The suite is bimodal in nature with minor amounts of basalt, gabbro and dolerite dykes == Tosham Hill range Indus Valley civilization mines and smelters ==