You finally managed to post something slightly relevant, although of course it didn't hold water. (I thought the 'storm in a sieve' idiom was pretty good).
The best part from that article was that the garimpos manged to mine 10 tons of gold from Eldorado do Juma which we know bled off a gabbro intrusion:
"Gold (at Eldorado do Juma) is typically located along the vertical joints (at least 3 mineralised joint/fracture planes were noted by Amazon Geoservices) and also along the bedding surfaces. This suggests low pressure hydrothermal mineralisation. Strong stockwork veining is present in the Gabbro unit that is found at the base of the sediment and intercalated volcanic package. This Gabbro has been identified over 4km of strike and is highly likely the source to the hydrothermal fluids that have deposited the gold along fractures and veins in the sediments."
from Eldorado do Juma which we know bled off a gabbro intrusion:
