Isograd

In geology, an isograd is a plane of constant metamorphic grade in the field; it separates metamorphic zones of different metamorphic index minerals. On geologic maps focusing on metamorphic terranes (or landscapes underlain by metamorphic rocks), the boundaries between rocks of different metamorphic grade are commonly demarcated by isograd lines....
Found on http://en.wikipedia.org/wiki/Isograd

isograd

(from the article `metamorphic rock`) Reactions that introduce new minerals in rocks of a specific bulk composition are referred to as mineral appearance isograds. Isograds can be mapped ... ...significant cooling. Nappe formation is a major process of crustal thickening during continent-continent collision; emplacement of the nappes .....
Found on http://www.britannica.com/eb/a-z/i/44

isograd

A line on a map joining points at which metamorphism took place under similar temperature and pressure conditions, as indicated by rocks belonging to the same metamorphic facies . Generally, the line separates two adjacent metamorphic zones, as indicated by specific .
Found on https://www.encyclo.co.uk/local/22327

Isograd

A line on a map that represents a specific degree of metamorphism. Rocks on one side of the line hav
Found on http://www.encyclo.co.uk/local/22392

isograd

A line or curved surface connecting rocks that have undergone an equivalent degree of metamorphism.
Found on http://www.scientificpsychic.com/etc/geology-glossary.html

isograd

line connecting points of similar conditions during geological metamorphism
Found on http://phrontistery.info/i.html
No exact match found