TECTONIC ACTIVITIES EFFECTS on MINERALIZATION IN HORMUZ ISLAND, PERSIAN GULF, SOUTHERN IRAN

Hormuz Island as an originally salty-gypsum diapir is located in the Persian Gulf, southern Iran. It includes many types of rocks and minerals ranging in age from Pre-Cambrian to recent. Rocks are not only: igneous, metamorphic, metasomatic, sedimentary and volcanoclastic, but also including many other types of ore deposits, evaporates and hydrothermal veins. Generally the Island is quite active either from diapirism point of view or from plate tectonics activities and plate’s movements. Consideration of salty gypsum diapirs in Iran is very important, because Iran is in the first place in this regard. More than 500 salty gypsum diapirs as exposures or hidden could be distinguish in south and Central Iran. Although they are quite different in shape, position and many other characteristics, but based on age they could be divided into two main groups: old group (500-800 my) or south Zagros group, (including Hormuz Island); and young group or Great Kavir group (Tertiary age related diapirs 60 and /or <60 my old). During the last decades many researchers have followed this subject putting their attentions on geological considerations and tectonic studies of the diapirs, but fewer attentions were made on this subject (the title of this paper) particularly in case of Hormuz. Because it is not only a diapir but also it is an island being in direct contact with sea water for a long period of time. It is also one of the most southern diapirs of the Zagros group and close to convergent boundary of the Iran micro plate and the Arabian plate sub-ducting northward beneath the Iran micro-plate. However position, composition and environmental conditions resulted in Hormuz Island unique diapir, not only from tectonic activity but also from many other characteristics point of view. Moreover diversity of rocks in Hormuz could be indication of a diapir with a different type of origin in compare to many adjacent or un-adjacent diapirs. This means that magmatic activity in this area could play an effective role not only in formation of Hormuz, but also in mineralization, ore formation, chemical composition, metasomatism, metamorphism, rock diversity, tectonic movements, geothermal regime, salt- gypsum origin and evolutionary path of the Island.

In general, magmatic and tectonic activities are mainly coincidence in many places, e.g. in mid ocean rifts or divergent boundaries, in convergent boundaries, and so on. However it is yet unknown that, which one is the first and which one is the second (tectonics, or magmatic activities)? It is similar to story of egg and chicken origin!! Perhaps one of the main problems concerning the Hormoz Island is to response to that question. It could be suggested that the whole boundary in WWN –EES trend (the Zagros boundary) was not so active in the past from magmatic point of view, but it was tectonically so active since Cretaceous time.

However there are many un-responded questions about the origin of the Hormuz Island, such as: What is the relationship between diapirism and magmatism? Did magmatism cause diapirism or vice versa?

Beyond to response to these questions, it is obvious that fracturing and tectonic activities have a great effective role in mineralization as a whole and in Hormuz in particular. Because mineralization needs: primary material (composition), space, path to go through, suitable thermodynamics conditions (P, T, t) and geochemical environments (Ph, Eh….), and finally home to crystallize, precipitate, deposit or growth. However diversity of minerals and mineralization in Hormuz are so great that needs too many details studies. Complexity of geochemical and geophysical conditions on one hand and diversity of thermodynamics, tectonic activities, changing of time scale and environmental conditions on the other hand and finally combination of part, parts or all of them under different circumstances: e.g. by changing gradually, quickly, suddenly or extremely, geochemical, geophysical conditions, compositions, space and time scale could had been resulted into the formation of too complicated rocks, minerals, ore deposits and fluids.