In Southwestern Spain there are various batholiths and plutons, mainly of adamellite composition, associated with basic-intermediate rocks, generally diorites and gabbros. These are all associated with epimetamorphic pelitic and carbonate rocks generally of Cambrian age. The basic-intermediate rocks, considered by some authors to be igneous rocks of mantle provenance, constitute "shallow" masses that gradually become granitic rocks with increasing depth.
The geological field data together with the petrographic and geochemical data appear to support the existence of a relationship between the nature of the sedimentary wall rocks and the origin and diversity of the plutonic rocks.
These basic-intermediate rocks are believed to have originated from the transformation of suitable sedimentary wall rocks by granitic rocks (mainly adamellites). The transformation by intrusive granites of pelitic sedimentary rocks produced "secondary" granitic rocks and also various quartzo-feldspathic rocks many of them wrongly interpreted as sedimentary rocks. When the granites affect marly of marly-carbonate rocks mafic minerals such as amphiboles, pyroxenes and sometimes olivines are formed. As a result, quartzo-diorites, diorites, gabbros and even some peridotites, as well as abundant granodiorites are produced.
The polyphasic character of these granitization processes have, in some cases, made basic rocks (e.g. gabbros) appear to be enclosed within granites like intrusive rocks. This caused many geologists and petrologists to interpret such rocks as later intrusive rocks from the mantle.