Details

Autor(en) / Beteiligte

• Davies, D. R.
• Rawlinson, N.
• Iaffaldano, G.
• Campbell, I. H.

Titel

Lithospheric controls on magma composition along Earth’s longest continental hotspot track

Ist Teil von

• Nature (London), 2015-09, Vol.525 (7570), p.511-514

Ort / Verlag

London: Nature Publishing Group UK

Erscheinungsjahr

2015

Quelle

EBSCOhost Psychology and Behavioral Sciences Collection

Beschreibungen/Notizen

• A 2,000-kilometre-long volcanic hotspot track is identified in eastern Australia, along which magma composition and volcanic outcrop show a strong correlation with lithospheric thickness, providing an observational constraint on the sub-continental melting depth of mantle plumes. Earth's longest continental hotspot track Rhodri Davies and co-authors identify an approximately 2,000-km-long hotspot track across eastern Australia that displays a record of volcanic activity between around 33 million years and 9 million years ago, which they name the Cosgrove track. Geological data together with plate-motion reconstructions and seismology suggest that variations in lithospheric thickness exert a first-order control on the occurrence of volcanism and magma composition along the track. The authors calculate a predicted present-day location for the mantle plume that generated this track, which coincides with a region of recent seismicity. Hotspots are anomalous regions of volcanism at Earth’s surface that show no obvious association with tectonic plate boundaries. Classic examples include the Hawaiian–Emperor chain and the Yellowstone–Snake River Plain province. The majority are believed to form as Earth’s tectonic plates move over long-lived mantle plumes: buoyant upwellings that bring hot material from Earth’s deep mantle to its surface 1 . It has long been recognized that lithospheric thickness limits the rise height of plumes 2 , 3 , 4 and, thereby, their minimum melting pressure. It should, therefore, have a controlling influence on the geochemistry of plume-related magmas, although unambiguous evidence of this has, so far, been lacking. Here we integrate observational constraints from surface geology, geochronology, plate-motion reconstructions, geochemistry and seismology to ascertain plume melting depths beneath Earth’s longest continental hotspot track, a 2,000-kilometre-long track in eastern Australia that displays a record of volcanic activity between 33 and 9 million years ago 5 , 6 , which we call the Cosgrove track. Our analyses highlight a strong correlation between lithospheric thickness and magma composition along this track, with: (1) standard basaltic compositions in regions where lithospheric thickness is less than 110 kilometres; (2) volcanic gaps in regions where lithospheric thickness exceeds 150 kilometres; and (3) low-volume, leucitite-bearing volcanism in regions of intermediate lithospheric thickness. Trace-element concentrations from samples along this track support the notion that these compositional variations result from different degrees of partial melting, which is controlled by the thickness of overlying lithosphere. Our results place the first observational constraints on the sub-continental melting depth of mantle plumes and provide direct evidence that lithospheric thickness has a dominant influence on the volume and chemical composition of plume-derived magmas.