Thin oceanic crust is formed by decompression melting of the upper mantle at mid-ocean ridges, but the origin of the thick and buoyant continental crust is enigmatic. Juvenile continental crust may form from magmas erupted above intraoceanic subduction zones, where oceanic lithosphere subducts beneath other oceanic lithosphere. However, it is unclear why the subduction of dominantly basaltic oc...

Chaldoran area in NW of Iran has Mesozoic oceanic crust basement. The studied rocks of this region can be divided into three groups: ophiolitic gabbros and pillow lavas, ophiolitic volcanoclastics and Eocene lava flows. Ophiolitic mafic rocks show continental volcanic arc natures and Eocene lava flow shows OIB-like nature. During the Mesozoic,the Chaldoran region was situated in the active cont...

[1] We perform travel-time tomography to estimate detailed seismic velocity structures in the crust of the Pacific slab from northeastern (NE) Japan to the Kanto district, Japan, and reveal that the depth extent of the low-velocity (hydrated) oceanic crust varies along the arc. The low-velocity oceanic crust is subducting to depths of 120–150 km beneath Kanto, which is 40–70 km deeper compared ...

chaldoran area in nw of iran has mesozoic oceanic crust basement. the studied rocks of this region can be divided into three groups: ophiolitic gabbros and pillow lavas, ophiolitic volcanoclastics and eocene lava flows. ophiolitic mafic rocks show continental volcanic arc natures and eocene lava flow shows oib-like nature. during the mesozoic,the chaldoran region was situated in the active cont...

Teleseismic converted phases are used to probe the composition of the downgoing oceanic crust as a function of depth along the Cocos slab in central and southern Mexico. Previously, modeling of the receiver function (RF) conversion amplitude of the flat Cocos slab beneath central Mexico at 45 km depth revealed a thin low-velocity upper oceanic crust of a thickness of 471 km, which has much lowe...

[1] Seismic tomography has revealed two large low shear velocity provinces (LLSVPs) in the lowermost mantle beneath the central Pacific and Africa. The LLSVPs are further shown to be compositionally different from their surroundings. Among several hypotheses put forth in recent years to explain the cause of the LLSVPs, one postulates that they are thermochemical piles caused by accumulation of ...

The average chemical compositions of the continental crust and the oceanic crust (represented by MORB), normalized to primitive mantle values and plotted as functions of the apparent bulk partition coefficient of each element, form surprisingly simple, complementary concentration patterns. In the continental crust, the maximum concentrations are on the order of 50 to 100 times the primitive-man...

The boundary between the crust and the mantle was discovered by Mohorovicic in 1909 under the European continent. Subsquent research in this century established the major differences between the continental and oceanic crust; a typical thickness for the continental crust is 30-50 km while a typical thickness for me oceanic crusts is 6 km. In terms of history the continental crust contains a muc...

JULY 2005, GSA TODAY ABSTRACT The subduction factory processes raw materials such as oceanic sediments and oceanic crust and manufactures magmas and continental crust as products. Aqueous fluids, which are extracted from oceanic raw materials via dehydration reactions during subduction, dissolve particular elements and overprint such elements onto the mantle wedge to generate chemically distinc...

Magnetic anomalies associatedwith new ocean crust formation in the Adare Basin off north-western Ross Sea (43–26Ma) can be traced directly into the Northern Basin that underlies the adjacent morphological continental shelf, implying a continuity in the emplacement of oceanic crust. Steep gravity gradients along the margins of the Northern Basin, particularly in the east, suggest that little ext...