Hello, Davit.

The answer to this question is, no.

MORB Basalts generate in the Mid-Ocean-Ridge. When you have an ocean-continent collision, partial melting occurs from the Slab (basaltic composition) and this magma go up to the continental crust and here there is a magmatic differentiation where the magma composition gets acid (granite).

There is a geochemistry explanation about compatible and incompatible elements to have ultrabasic, basic, intermediate or acid magmas on different zones.

You can see this: http://research.uvu.edu/Bunds/Geol101H/Handouts/volc_proc_summ.pdf

MORB Basalts do not generate in an ocean-continent collision zone.They can occur as ophiolites.

No, but the presence of cumulates (aggregates of mafic minerals) can misinterpret mafic (or mafic tendency - intermediate) sample rocks of a convergent boundary into MORB field in some of the diagrams (like the diagram of Pearce and Norry, 1979).

Still, convergent boundaries have basalts of their own called island arc basalts (IAB).

Thanks everyone for useful suggestions. Ahmad can you tell me the cumulates are contaminated or not? e.g. Ru/Sr isotopes or other REE elements?

Regards

David

In case of cumulates, smaples will show lower Zr and higher Y.

Cumulates are indications that rocks underwent long periods of hot circulating fluids interactions (see Gill, 2010). In case of contamination from continent (check high Rb values) , the samples will shift to WP field of Pearce and Norry (1979) or show affinity to WPG of Pearce et al. (1984), check the diagram of Pearce and Gale (1977) to investigate overlap to within plate magma.

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One can find them there even if they are not formed there (i. e. emplaced by obduction, as Jan Golonka suggests, or by later thrust tectonics). Ocean-continent collision sounds a bit unusual, normally is it about a subduction zone as ocean crust gets subducted along the continental active margin - possibly also accompanied by subordinate obduction. If the rocks are basalts, the discussion about cumulates seems rather out of place, unless the diagnosis is entirely based on chemistry, in which case we don't know for sure what the rocks are. Looking at them helps a lot, as much as the field relationships.

Dear Colleagues,

Thanks for all of your scientifically suggestions and advices.

Regards,

David

My answer to your question is NO. MORB is produced in the mid-ocean ridge setting, but cannout e generated in a collisonal zone between ocean and continental plates.

I totally agree with Yariv Díaz and Xue-Ming Yang. MORB is abbreviation for Mid-Ocean Ridge Basalt. That is it. There are chemical variations in oceanic basalts, but they are different than subduction-related basalts. But some of the early arc basalts may be confusing.

The tectonic transport and emplacement of MORB in alien environments is an all together different matter. Here we are talking about their tectonic locale at the time of origin.

Variation diagrams based on basaltic rocks should not be used indiscriminately for cumulates and plutonic rocks.