Please answer the following questions below using the map above. The figure abov
ID: 110278 • Letter: P
Question
Please answer the following questions below using the map above.
The figure above shows large outcrops of several kinds of rocks, metamorphosed to varying degrees. Between the outcrops the rocks are covered with soil and other surficial sediment. The parent rocks for these metamorphic rocks are identified by various colors. The number on the outcrop refers to the samples described below the map.
(a) Where applicable, mineral names modify rock names and indicate the metamorphic zone.
(b) Where on the map is te metamorphism most intense? Least intense?
(c) which parent rocks best record differences in metamorphic grade?
(d) which parent rocks are least helpful for determining metamorphic grade?
(e) using the index minerals as a guide, draw isograds on the map and label the mineral zones between them.
Please answer.
Soll and Parent rocks 12 Brown shale 15 19 10 Red shale 5 km sandstone L 16 Green shale 24 26 Sample no Description 16 17 18 19 20 21 Limestone Chlorite phyllite Biotite schist Garnet schist Staurolite schist Quartzite Kyanite schist Kvanite schist Chlorite phyllite Quartziie Chlorite slate Quartzite Biotite sclalst Marbie Garnet schist Garnet schist Quartzite Staurolite schist Marble Limestone Green shale Chlorite slale Quartz sandstone Quartzite Chlorite phyllite Biotite schist Marble Marble Garnet schist 12 13 i4 15 Garnet schisExplanation / Answer
(a) Metamorphism is a change of minerals or geologic structure in parent rocks with the help of heat, pressure and chemically active fluid. As the heat and pressure increses the chemically active fluid also increses and it leads to icreses metamorphic grade from low to high. As a diagram shows in question it mostly indicate the metamorphism of that particular terrain where the rock contain particular minerals like Grey Shale mostly contain limestone and marble which shows regional as well as thermal metamorphism.Red Shale mostly contain chlorite phyllite, biotite schist, garnet schist, staurolite schist, kyanite schist which shows barrovian zone(medium pressure zone) types of metamorphic zones. Quartz Sandstone mostly contain quartizite and green shale contain moderate to high grade of metamorphism like chlorite slate, biotite slate, garnet schist, green shale and chiorite slate. Most of them cover barrovian type of zone in which both pressure and temperature increase gradually along the metamorphic gradient. Barrovian metamorphism takes place during regional metamorphism, caused by crustal thickening in the roots of an orogenic belt. Barrovian zones are especially easy to recognize in pelitic rocks.
(b) Towards the green shale there is intence metamorpism has occured because the rock shows variation from schist to slate where temperature as well as pressure increses.Slate is high grade metamorphic product in medium pressure zone and the least metamorpism has occurred near by Quartz Sandstone which is regional type of metamorphism.
(c) Red Shale shows best record of differences in metamorphic grade because as earliar i said there is presence of whole sequence which contain barrovian zone (medium pressure zone). The lower most chlorite zone to high pressure and temperature kyanite zone.
(d) Quart Sandstone is formed by regional metamorphism which contain Quartzite only. That indicate monomineralic composition at particular temperature and pressure.
(e) Extremly sorry. I do not have any source to draw isograds on map and to label the mineral zones between them.