Varieties of the Himalayan eclogites: A pictorial review of textural and petrological features

A pictorial review and brief description of metabasites (mainly eclogites) exposed in the western part of Himalaya, north Pakistan are presented. The metabasites occur in the Kaghan and Neelum valleys in the form of thick sheets, dikes, lenses, and zoned bodies. On the basis of petrography and mineral paragenesis, they can be distinguished into greenschist, amphibolites, garnet-amphibolites, eclogites, amphibolitized eclogites, and garnetites. In this review, first a brief history of the term eclogite and its origin for understanding the process of eclogite formation is presented. Then, a description on the occurrence of various metabasites/eclogites outcrops in the western Himalaya is given. Later, detailed petrological and textural features observed in hand specimen and under the microscope are discussed for individual rock types. Finally, an overview of the Himalayan metabasites tracing back from their magmatic basaltic source to their transformation into amphibolites and eclogites via multi-stage metamorphism is provided. The field features, with the aid of petrological and geochemical evidence of these metabasites, help to constrain the tectono-metamorphic evolution of the continent–continent collision type orogenic belts such as the India–Asia collision-related Himalayan metamorphic belt.