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This is an extraordinary outcrop.
Not least, because the person seen is Dr. Nitin Karmalkar, current Vice Chancellor of 'SPPU'.
The rocks are fragments of the earth's mantle, thrust up during India-Asia convergence.
Short Thread- Ophiolites of the Indus Suture Zone.
Not least, because the person seen is Dr. Nitin Karmalkar, current Vice Chancellor of 'SPPU'.
The rocks are fragments of the earth's mantle, thrust up during India-Asia convergence.
Short Thread- Ophiolites of the Indus Suture Zone.
Dr. Karmalkar is an igneous petrologist, working mainly on ultramafic rocks (high Mg content, low silica). His PhD work was on chromite mineralization in ultramafic rocks of the Indus valley, Ladakh.
What are ophiolites?
They are slices of oceanic lithosphere which are scraped off the subducting plate and thrust up during convergence/collision of two tectonic plates.
They are slices of oceanic lithosphere which are scraped off the subducting plate and thrust up during convergence/collision of two tectonic plates.
Where do ophiolites originate?
Oceanic lithosphere forms at plate spreading centers such as mid-oceanic ridges and more rarely at 'back-arc centers'.
As plates diverge, mantle upwells and partially melts. Chemical segregation of melts results in a suite of rocks.
Oceanic lithosphere forms at plate spreading centers such as mid-oceanic ridges and more rarely at 'back-arc centers'.
As plates diverge, mantle upwells and partially melts. Chemical segregation of melts results in a suite of rocks.
Oceanic lithosphere that became the Indus ophiolites formed around 150-140 million years ago at a plate spreading center, when Gondwanaland was beginning to break up. Subsequently as India drifted northwards this lithosphere became the leading margin of the India plate.
The graphic shows evolution of Indus suture zone (ISZ) as India subducted under Kohistan-Ladakh arc & then collided with the Asia mainland. The ISZ contains the ophiolites which were thrust up during this welding of plates. Leh sits on the Ladakh arc.
https://www.sciencedirect.com/science/article/abs/pii/S1342937X12002390?via%3Dihub
https://www.sciencedirect.com/science/article/abs/pii/S1342937X12002390?via%3Dihub
This is an idealized ophiolite rock suite. The lower layers are the earth's mantle. The Moho and the transition zone marks the passage to the earth's crust. Mantle melts rise and erupt forming ocean crust of basaltic composition (pillow lavas).
https://www.researchgate.net/publication/233947458_Podiform_chromite_deposits_database_and_grade_and_tonnage_models
https://www.researchgate.net/publication/233947458_Podiform_chromite_deposits_database_and_grade_and_tonnage_models
The first pic I posted shows the mantle levels of this Indus ophiolites. The lower dark rubbly looking rocks are harzburgites and the upper light brown rocks are dunites. Dr. Karmalkar is standing somewhere close to the mantle-crust transition zone!
This SW-NE cross section captures the arrangement of terrains in ISZ in the Nidar valley, Ladakh. The Tso-Morari crystallines marks northern margin of Indian continent. Ladakh granites marks S margin of Asian continent. Sandwiched are the Indus ophiolites within the suture zone.
Look closely at X-section. From S to N exposes shallower levels of the ophiolite sequence. Mantle rocks like harzburgites r heavily altered by reaction with sea water to serpentine. Sequence is capped by pillow basalts & finally deep ocean sediment.
fig- https://www.sciencedirect.com/science/article/abs/pii/S0009254120303119?via%3Dihub
fig- https://www.sciencedirect.com/science/article/abs/pii/S0009254120303119?via%3Dihub
This is a NW looking view of the Nidar valley. The mountain range in the extreme background is the Ladakh granite (Asian plate). Mantle rocks like harzburgites and dunites in the foreground intruded by gabbro (the darker ledges).
pic credit: Dr. Raymond Duraiswami
pic credit: Dr. Raymond Duraiswami
Dr. Karmalkar's work on the Indus ophiolites is being expanded by his students today. Many thanks to Dr. Raymond Duraiswamy for the outcrop pic. And I recommend his recent talk on the Indus ophiolites available on YouTube.
Oceanic lithosphere that is created at mid-oceanic ridges is destroyed at subduction zones where it is returned to the mantle. Occasionally fragments of these oceanic plates survive as ophiolites, bearing imp. information about mantle process and plate recycling.
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