Big river Gold exploration, discussion: part 2

This article is part 2 of our discussion into the Big River Gold Exploration Series. In this article I will layout the basics of the geology of the area, our initial findings with the 4-inch dredge and if I think the trend, we are searching for cross this area. Once again if you haven’t watched the second video, you can find it at the bottom of the page. If you haven’t read part 1 of this series, you can find it here: Big River Gold Exploration Series Discussion : The Prospecting Geologist

Geology Break down

I will start where I left off in Part 1, discussing the geology. Below you can see a geologic map of the Trend Area 1. Most of our sampling took place on top of the bedrock labeled Trss. This is mapped as Triassic aged Siltstone/sandstone. However, geologic maps often simplified compared to what you find in the field. And in reality Trss had a good amount of Trc which is a breccia/conglomerate, interlayered within. This is a good thing as there is a precedent for conglomerate/breccia to hold gold when compared to a sandstone/siltstone.

The basin that the siltstone/sandstone/conglomerate/breccia formed in are made up of material eroded from the surrounding area. So, if there was gold mineralization in the surrounding area then the conglomerate/breccia could have gold in it. There are a few gold mines and prospects in similar conglomerate/breccias in NC. This type of deposit would be considered a paleo placer/fossil placer. And hence isn’t a primary source.

If there is gold in the conglomerate/breccia, it would have eroded from Cep and/or wp. With the abundant quartz veins and stringers in the surrounding Cep and wp being a possible primary source for the area. We have panned some gold out of the surround small streams that flow over only Cep and wp. This points to at least some gold weathering out of the quartz in these formations. The question is, is it enough to form a deposit that will produce 1 gram a day with a 4-inch dredge.

Another source that is possibly related to the N-S trending area of gold is a number of diabase dykes that cut N-S through the area. In the areas where these dykes cut the Triassic basins there is minor amounts of documented copper mineralization due to hydrothermal alteration. With this in mind there is certainly a chance of minor gold mineralization with the copper. However, we didn’t come across any of these during our exploration.

Hitting the River

Getting out to dredge a new location for the first time, always puts hope of dreams of tons of gold in your head. This type of mindset is needed when prospecting new areas, but it can be hard to maintain as reality seldom matches our dreams and delusions of grandeur. However, if a sampling plan is to be maintained, expectations must be kept in check, since small finds and clues can lead the way to good gold. It just takes time and effort.

For this first trip with the proline 4 inch dredge the river was at a good level but a bit murky, which isn’t ideal. One of the main goals we had was to determine if the N-S trending feature we saw on google earth was a quartz vein or something else. As it turns out it was just a rib of the normal bedrock, not a quartz vein.

With one of the main objectives completed for this trip we set about figuring out where to dredge. As fate would have it our cooler tipped over. As we were wrangling its contents, we noticed the area had some large boulders and cobble. So, we decided to set up the dredge there. And after about a 30 min run, we decided to check the box. And wouldn’t ya know we had some nice flakes in the top mat!

The material was loose on top to about 6 inches down then changed to a nice tan cobble hardpack. The hardpack was from 1 to 2 feet thick to bedrock. This particular sample hole may have been uncharacteristically rich due to the layout of the bedrock. This is due to the conglomerate overlaying the siltstone. This formed some deep trenches which turned out to be abnormal for the area.

The pay layer was the tan cobble hardpack, with gold distributed throughout it. We determined this by seeing gold in the hardpack as well as on bedrock. Being able to see even small amounts of gold while dredging goes a long way in telling you where the pay layer is.

Conclusion

While this was merely a day trip, it provided some great information, which pointed towards a possibility of good gold in the area. The goal for future trips would be to find out if the gold we found was average, a lot, or a little for this area. This requires sampling other parts of the river with a focus on changes in bedrock type. That is what we will focus on discussing in part 3 next week.