tax_query OR meta_query… possible?

It appears that when creating a custom query, the operator that’s applied to a tax_query and a meta_query is ‘AND’.

Is it possible to have a query that selects something from a category (tax_query) OR from a custom field (meta_query) ?

$args =  array (
		  'post_type' => 'post',
		  'meta_query' => array (
			array(
			      'key' => 'key_name',
			      'value' => 'val_name'
			      )
			)
                   'tax_query' => array (
                            array(
                                 'taxonomy' => 'category',
			         'field' => 'slug',
			         'terms' => array( 'quotes' )
                             )
                         )
		  );

I’m finding that this query provides me with a result of a category AND a custom field… but I’d like to have a category OR a custom field…

possible?