Composition of Martian Crust
The most abundant elements are:

Element  Approximate % by weight

Oxygen        46.6
Silicon       27.7
Aluminum       8.1
Iron           5.0
Calcium        3.6
Sodium         2.8
Potassium      2.6
Magnesium      2.1
All others     1.5


Source:http://hyperphysics.phy-astr.gsu.edu/hbase/Tables/elabund.html

Based on data from a number of NASA and ESA spacecraft and rovers, 
(Fine summary on wikipedia: https://en.wikipedia.org/wiki/Composition_of_Mars). The four top elements are most likely the same. They are roughly the same on Mars and Earth and may be in the basic proportions  


Oxygen      
Silicon
Aluminum
Iron


I would expect at some point that the relative abundance of elements on Mars to deviate from that on Earth based on the following differences:


Earth and Mars were most likely formed at two very different distances from the center of our solar system.  This may have significantly affected the elemental abundances between the two planets.
Earth has had significant amounts of water since from very early in its history, as recorded by some of the oldest rocks on Earth which are meta-sedimentary deposits in Australia.
We do not known how much water has ever been on Mars. Mars is currently very dry.  Water plays a big role in element distribution on Earth and my guess is water will have played a smaller role on Mars.
Lastly, I am becoming convinced that biologic activity has also significantly affected element distribution on Earth.  Bacteria/Archaea have been found in deep rocks in South African gold mines, which is remarkable. Bacteria and Archaea may play a larger role in various geological processes than traditionally thought.  The Mantle is no longer viewed has dry and sterile.  
Life on Mars (even as  Bacteria/Archaea) is yet to verified.