This graph shows that range, tonnes per percent metal. Size...

This graph shows that range, tonnes per percent metal. Size along the x-axis varies from 1 million tonnes up to a huge 400 million tonnes with the mean standing around about 20 million tonnes. Lead and zinc grades, that’s the y- axis, ranges from 3% up to 30 %, with a mean of about 10-12%. As you can see, SEDEX deposits are both much bigger than VMS deposits and have better grades, making them highly desirable exploration target.Problem of course is that they are much less common. In spite of their scarcity, they are a large source of the world’s lead and zinc SEDEX deposits range in age from the mid-Proterozoic that is 180 million years ago to the Phanerozoic, 150 million years ago. The Sullivan in Southeast British Columbia is 150 million tonnes making it a larger than average SEDEX deposit, but the grades are pretty much average with about 11% combined of lead and zinc.