Yes it does. Other minerals weather to clays more quickly. I recommend some reading on "Bowen's Reaction Series". It outlines when minerals form in a cooling igneous melt. In general, turn it around for a weathering series.

You are correct, there are probably clays there. The olivine we discussed also breaks down into clay.

However:

While the weathering of minerals to clays requires water, the big question is how much water? Not much, really. You don't need rivers or seas or even that much water at all if you expose it to a very small amount of water over an extended period of time, like hundreds of millions of years. The plagioclase is fairly fresh just under the crusty weathering surface.

The majority of the weathering I see in this area is mechanical.

The plagioclase in this rock does not supply all the answers to the observed chemistry. Especially the Titanium and Phosphorus. I've been hearing rumors of elevated REE's. (Which would fit an earlier speculation.) We still don't know what the wedge / arrow shaped minerals are, or what that hexagonal psuedomorph is / was. We don't know which plagioclase this is, that distiction has important implications for the rock type, but will be difficult to discern here.

Because there are elements here that play important roles in biology does not mean they are biogenetic.