Average Age Of Continental Granite Vs Basaltic Plate

Basalt is more common in oceanic crust while granite is more common in continental crust.

Average age of continental granite vs basaltic plate.

Basalt is denser and heavier than the granite that makes up continental plates. That s when the thickness and composition of continental crust come into play. The low ɛnd t 13 8 to 19 5 ε hf t 14 6 to 24 4 and 206 pb 204 pb i 16 244 to 17 304 are consistent with significant contributions of the lower continental crust to magmas parental to the laoshan granite. The basaltic melt from the hotspot stem may in fact form two levels of magma chambers within the overriding plate.

Plate motion carries the region of extensive basalt lava away but the magma rising from the stem must somehow work its way to the surface. Basalt wikipedia wikimedia foundation 13 sept. Basalt can form in a few days to months whereas granite plutons can take millions of years to cool and harden. In some mostly early archaean cratons composite granite batholiths form ovoid structures surrounded by volcano sedimentary sequences.

This ratio is far higher than seems likely if the sial had been entirely derived. The origin of the parental magmas is best understood as resulting from anatexis of the lower crust 20 25. This is because oceanic crust is constantly being recycled at convergent plate boundaries where an oceanic plate meets a continent. The average age of oceanic crust is about 55 million years compared to an average age of 2 3 billion years for continental crust.

Basalt and granite are two types of igneous rocks that we can find on earth. Continental crust is broadly granitic in composition and with a density of about 2 7 grams per cubic cm is somewhat lighter than oceanic crust which is basaltic i e richer in iron and magnesium than granite in composition and has a density of about 2 9 to 3 grams per cubic cm. The key difference between basalt and granite is that basalt is mostly occurring on ocean floors while granite is in the crust of the earth in all continents. Continental crust is typically 40 km 25 miles thick while oceanic crust is much thinner.

Granite greenstone terranes typically contain more than 60 granitic rocks of varying age composition and degrees of deformation and metamorphism de wit and ashwal 1997 b. Over the approximately 4 ga of the continental rock record the average composition of preserved continental basalts has evolved along a generally continuous trajectory with decreasing compatible element con centrations and increasing incompatible element concentrations punctuated by a comparatively rapid transition in some variables such as la yb ratios and zr nb and ti abundances approximately 2 5 ga ago. Summary basalt vs granite. When an oceanic plate meets a continental plate at a convergent boundary the oceanic plate is forced under the continental plate and destroyed.

It seems that sial of the composition of the average igneous rock constitutes fully 26 and perhaps as much as 43 of the total crust.