add to funtions.php:

add_action( 'wp_print_styles',     'my_deregister_styles', 100 );

function my_deregister_styles()    { 
   //wp_deregister_style( 'amethyst-dashicons-style' ); 
   wp_deregister_style( 'dashicons' ); 


}

add_action( 'wp_print_styles', 'tn_dequeue_font_awesome_style' );
function tn_dequeue_font_awesome_style() {
      wp_dequeue_style( 'fontawesome' );
      wp_deregister_style( 'fontawesome' );
}