Would it be possible to put a design feature between the pieces of marble? A butcherblock or some kind of wood seam for example? Or a strip of a second kind of stone? Your island is narrow enough to make this workable.

Could one of the marble pieces be cut in two to fit the two ends, allowing the large piece to be centered in the island, bumping the joints to the sides where they would look more intentional? This would put seamless material into the center of the island where I assume it would be less of a visual and utilitarian intrusion.

Since the island is a major workhorse in your kitchen, maybe having the Ocean Grantique there would be a good thing. Maybe you could go with cararra on any perimeter counter space. I LOVE white marble but I'll tell you, if that Ocean Grantique is what I think it is, ooh la la!! You just can't go wrong between those two choices.
To touch on what Florantha suggested, I see quite a bit of islands being slightly dropped in one area, like on the end, topped with marble and dubbed "baking" zone. I think it looks great, I bet it functions well too.

My island will be topped in Carrara and measures 44" x 180." Roughly in the center there will be a 30"prep sink (on the other side of the prep sink will be the range with a 60" supporting wall separating them). Two slabs will be used. I am okay with this because the island is huge...what else would they do?

My recommendation for you would be to post asking to see people's seems in their marble. To seam it they will use white epoxy. The more consistently white your marble is, especially if it is honed, the less noticeable the grout line will be.

Have you considered stainless steel? It goes well with white marble and white cabinets.

All I could find for Ocean antique is a slate called ocean in an antique finish. It seams to be imported from India.

I don't know personally the truth to this, but I've heard American Slate makes a great counter (that ages over time-but doesn't etch). Vermont green slate is the benchmark stone - pale green-gray, no oiling.

Indian slate is apparently known for flaking and breaking.

Thanks for the responses!

To my eye, the Ocean Antique looks like honed Verde Lavras--a deep gray-green with black and occasional white. I think it's the fabricator's solution to meeting demand for soapstone, at granite prices. For those who have seen the Mamadadapaige kitchen (one of my favorites!), the coloring is very similar.

Florantha and others, I'm trying to figure out how to post my floor plan, but in the meantime, I've attached a link to a photo I found of a kitchen with a layout and design scheme very similar to mine. The main difference is that my island is a rectangle, without the round piece at the seating area. Flooring, backsplash and appliance placement are similar.

Maybe mixing the countertops is the way to go?

Here is a link that might be useful:

I have a seam in my carrara marble and it came out very bad. I used a company in Virginia, Rugo . Good luck.