Cen­tral Otago rocks re­veal earth’s se­crets

Central Otago Mirror - - FRONT PAGE - JO MCKEN­ZIE-MCLEAN

Cen­tral Otago rocks are help­ing Aus­tralian ge­ol­o­gists un­der­stand how the earth has de­vel­oped through time and how it might con­tinue to de­velop.

Monash Univer­sity schol­ars Casey Blun­dell and Mitchell O’Mara are con­duct­ing field re­search around the Millers Flat, Alexan­dra and Danseys Pass ar­eas, as well as other parts of cen­tral Otago, as part of Blun­dell’s PhD look­ing at the struc­tural and tec­tonic evo­lu­tion of the Otago re­gion.

Blun­dell said she had a par­tic­u­lar in­ter­est in the role of the Alpine Fault – a ma­jor plate boundary be­tween Aus­tralia and New Zealand.

‘‘There is a lot of (geospa­tial) data avail­able for the Otago area that de­serves de­tailed study. There have been few com­plete in­ter­pre­ta­tions and not much is known about what this data ac­tu­ally means. The area has a com­pli­cated his­tory to un­ravel.’’

Part of her re­search uses the mag­netic prop­er­ties of the rocks to cre­ate a ge­o­logic map, and is im­por­tant for un­der­stand­ing the three-di­men­sional struc­ture of the earth, she said.

‘‘This has im­pli­ca­tions for un­der­stand­ing how Otago and the Earth has de­vel­oped through ge­o­logic time and how they might con­tinue to de­velop. The evo­lu­tion of folds or faults you can see in rocks around here, in­flu­enced by pres­sures as far away as the Alpine Fault – how move­ment along that fault is dis­trib­uted down through into Otago is what I am in­ter­ested in.

‘‘By ob­serv­ing how the folds are mov­ing and de­vel­op­ing here, we can be­gin to un­der­stand how everything has to move a lit­tle bit in or­der for a big struc­ture to move a lot.

‘‘I want to un­der­stand what mas­sive de­for­ma­tion (>800km) along a plate boundary af­fects the struc­tures here, and what that looks like in 3D.’’

Their re­search would help mul­ti­ple peo­ple, and has im­pli­ca­tions for the likes of min­eral and en­vi­ron­ment in­dus­tries, she said.

‘‘Map­ping the net­work of faults and struc­tures of the schist might tell us what pos­si­ble path­ways flu­ids have mi­grat­ing through the crust.

‘‘Flu­ids can carry and de­posit many things like gold and tung­sten in this part of the world, and in Aus­tralia flu­ids can carry cop­per, gold and iron ox­ides that are used in many ev­ery­day prod­ucts.

‘‘This sort of in­for­ma­tion can be used in a many dif­fer­ent ways – at a big scale to un­der­stand how the earth and con­ti­nents de­vel­oped, and at smaller scales how rocks are lo­cally de­formed and what this means for the lay of the land.’’

Ge­ol­o­gists Casey Blun­dell and Mitchell O’Mara.

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