Dianor Resources Inc V.DOR

potential of the archean conglomerates

[propertymad]

have a read below of some info in relation to semi - analagous paleoplacer deposit in India......

the beauty about this India conglomerate is the anecdotal evidence that over the course of history it has produced some of the most prized and valuable diamonds ever discovered.....

whether or not we find our 'proximal source' we can take comfort in the fact that the folding, sorting, alluvial, colluvial and genral 'winnowing' effects over 2.7bn years has left us with a high quality batch of diamonds ...... that Tavernier hinmself would have been proud of....


PALEOPLACER DIAMONDS OF WAIRAGARH, MAHARASTRA:

Diamond incidence is known from conglomerates of Wairagarh area in Maharastra

(Tavernier 1676). A brief account of the diamond incidence in Wairagarh area is as follows:

The Wairagarh area exposes a narrow stretch of (10km x 6km), NNW-SSE trending low

grade, highly deformed meta sedimentary belt within the terrain occupied by Archaean Amgaon

Gneiss and forms a part of the western part of Bastar Craton. The metasediments comprise

framework supported polymictic conglomerate, gritty and pebbly arenaceous units, quartzite and

quartz-mica schist. Polymictic conglomerate is made up of bizarre assemblage of clasts of

different composition and size set in a well-foliated quartz sericite matrix. Quartzite dominates

the clast population accounting nearly for 80%, and the remaining includes gneiss, vein quartz,

ferruginous quartzite, and metabasics. The deformed clasts display high degree of flattening and

the rock records variable (sub horizontal to steep) stretching lineation. The conglomerate grades

laterally in to gritty quartzite and mica schist. The ductile shear zone occurring along the eastern

margin of Sakoli Fold belt passes through the sediments resulting strong deformation of the

basement – cover rocks.

The Wairagarh metasedimentary unit (WMS) appears to have been deposited over the

gneissic basement. The Dongargarh granite dated 2465-2270 Ma by Sarkar 1994, occurs along

its eastern margin. A narrow lensoidal body of granite occurs within the WMS towards its

southcentral part. The lensoidal body of granite does not show any strain evidence. Younger

cover rocks of platformal facies of probable Pakhal rocks (mid to late Proterozoic) and lower

Gondwana affinity (Talchir) occur to the western and northwestern part respectively. The

stratigraphic status of WMS is still not clear. The total absence of granite clasts in the WMS and

the undeformed nature of granite as compared to the strained nature of the WMS suggest that the

granite may be intrusive, which may assign an early Proterozoic age to the WMS.

From the available records it is known that mining in Wairagarh area was prevalent since

the early part of 15th century. Farishta in 1425, Garcvia daorta in 1565 and Abul Fazal in 1590

(Ball, 1984) described the richness of the mines and the quality of the diamonds. From the

distribution of the old workings and abundant dumps it can be assumed that the entire area was

scanned for diamonds, including alluvial, colluvial, weathered bed rock and even the laterite

profile developed over the conglomerate. It appears that the clast rich portion was selectively

mined, as good crop of heavy minerals are associated with such coarse clastics. The workings

having a general size of 25m-40m diameters are seen spread throughout the area. Study of the

old dumps and stacks suggest that the old miners have removed the clasts at the site of pits itself

and the matrix was crushed to 1cm and 5mm size for recovery of diamonds.

An octahedral diamond (3.5mm long and 2.5mm wide, 0.15 carat) recently recovered

during the GSI investigations of the conglomerate unit of WMS shows a light greenish tint with

well developed crystal faces. The octahedra edges show stepped surfaces and twinning noticed is

of spinel law, having a triangular shape in plan. A black coating, noticed in a cavity on one face,

appears to be graphite inclusion. Along with diamond other heavy assemblages identified

include ilmenite, garnet (G-5 garnet, almandine, grossular and andraditic garnets), pyroxenes,

amphibole, staurolite, chrome spinel and rare tourmaline. The chrome pyroxenes are low chrome

variety. The Ca/(Ca+Mg) and Mg/Mg+Fe ratios of the pyroxenes do not indicate any

kimberlite/lamproite affinity.

The discovery of diamond in an older conglomerate of probable early Proterozoic age

points to much older diamondiferous intrusion in the western part of Bastar Craton. The source

rock of diamond probably of Archaean age may be difficult to locate due to complex geological

processes the terrain has undergone, which include granite intrusion, regional metamorphism

followed by deposition of younger proterozoic and Gondwana rocks. This find has opened up

new vistas of diamond search in similar geological milieu in the western Bastar Craton.