Should I use adjacent parentheses or a semicolon (or something else)?

In scientific writing it is common to use parentheses to refer to the details of statistical analyses at the end of a sentence. However, it is also common to refer to figures or tables this way. Often I find that the same sentence requires both a reference to statistical details and a figure (example below). Should I use adjacent parenthetical references or separate the statistical information from the figure reference with a semicolon?

Treatment A contained significantly greater mass than treatment B (p = 0.001)(Figure 1).

OR

Treatment A contained significantly greater mass than treatment B (p = 0.001; Figure 1).

Don't write pairs of parentheses back to back (don't do it)(no, really!). Either you can put on of the two items in the main text:

Treatment A contained significantly greater mass than treatment B (p = 0.001), as show on Figure 1.

or use the semicolon, as you proposed:

Treatment A contained significantly greater mass than treatment B (p = 0.001; Figure 1).

As this is a question about scientific writing, I suggest you consult a style manual specific to your field, or, if it's for publication, the publisher's style sheet. Different fields and different publishers may have different standard ways of dealing with this issue.