Sedimentology Home weathering Pronies The purpose of this lab is to review the mineralogy and geochemistry of weathering profiles developed on igneous and meta-igneous rocks. Weathering profiles are very important in the study of sedimentary rocks because when profiles are eroded by stream systems, clay minerals are separated from residual sand-sized particles. This separation of sands from muds by hydrodynamic processes creates the sediments and sedimentary rocks we are accustomed to seeing: sandstone, shale, conglomerate, etc. Chemical weathering plays a crucial role in the alteration of major-element geochemistry and mineralogy of siliciclastic sediments. Most of Earth's exposed crust is unweathered plutonic rocks, most of which have a chemical index of alteration (CIA) value of 50. This lab considers the geochemical and mineralogic changes when such rocks are exposed to acidic solutions in the weathering environment by calculating the CIA values for 7 real rocks from Australia. After erosion of the profile, this weathered material then becomes clastic sediment. Read all of these instructions carefully. There are questions and problems along the way that need to be answered. CIA= Al₂O3 (Al₂O3 + Cao + Na₂0+ K₂0) 1) A = CIA 6) A CIA 8) A =CIA 9) A =CIA 10) A =CIA 13) A = CIA 15) A-CIA The following data set (attached at the end of the lab packet) comes from a modern weathering profile developed on bedrock in Australia. Complete data sets through modern weathering profiles are relatively uncommon still, and to my knowledge this is the best of all available profiles. For samples 1, 6, 8, 9, 10, 13, 15 you need to do the following things: 1) Calculate CIA (remember to use molecular proportions) and give me the coordinates for CN and K (remember A = CIA). Note that in this exercise no value for CO2 is given, thus the only correction we have for CaO* is to subtract apatite following the equation: mol Cao* = mol CaO - 10/3 mol P2Os. Also remember, when CaO* = a negative number, set CaO* = 0 IMPORTANT keep this in mind: A+CN+K=100.00 This is a rule. CN CN CN CN CN CN CN K K x 100 K K K K K

Sedimentology Home weathering Pronies The purpose of this lab is to review the mineralogy and geochemistry of weathering profiles developed on igneous and meta-igneous rocks. Weathering profiles are very important in the study of sedimentary rocks because when profiles are eroded by stream systems, clay minerals are separated from residual sand-sized particles. This separation of sands from muds by hydrodynamic processes creates the sediments and sedimentary rocks we are accustomed to seeing: sandstone, shale, conglomerate, etc. Chemical weathering plays a crucial role in the alteration of major-element geochemistry and mineralogy of siliciclastic sediments. Most of Earth's exposed crust is unweathered plutonic rocks, most of which have a chemical index of alteration (CIA) value of 50. This lab considers the geochemical and mineralogic changes when such rocks are exposed to acidic solutions in the weathering environment by calculating the CIA values for 7 real rocks from Australia. After erosion of the profile, this weathered material then becomes clastic sediment. Read all of these instructions carefully. There are questions and problems along the way that need to be answered. CIA= Al₂O3 (Al₂O3 + Cao + Na₂0+ K₂0) 1) A = CIA 6) A CIA 8) A =CIA 9) A =CIA 10) A =CIA 13) A = CIA 15) A-CIA The following data set (attached at the end of the lab packet) comes from a modern weathering profile developed on bedrock in Australia. Complete data sets through modern weathering profiles are relatively uncommon still, and to my knowledge this is the best of all available profiles. For samples 1, 6, 8, 9, 10, 13, 15 you need to do the following things: 1) Calculate CIA (remember to use molecular proportions) and give me the coordinates for CN and K (remember A = CIA). Note that in this exercise no value for CO2 is given, thus the only correction we have for CaO* is to subtract apatite following the equation: mol Cao* = mol CaO - 10/3 mol P2Os. Also remember, when CaO* = a negative number, set CaO* = 0 IMPORTANT keep this in mind: A+CN+K=100.00 This is a rule. CN CN CN CN CN CN CN K K x 100 K K K K K

Applications and Investigations in Earth Science (9th Edition)

9th Edition

ISBN:9780134746241

Author:Edward J. Tarbuck, Frederick K. Lutgens, Dennis G. Tasa

Publisher:Edward J. Tarbuck, Frederick K. Lutgens, Dennis G. Tasa

Chapter1: The Study Of Minerals

Section: Chapter Questions

Problem 1LR

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Question

Chemical weathering plays a crucial role in the alteration of major-element geochemistry and
mineralogy of siliciclastic sediments. Most of Earth’s exposed crust is unweathered plutonic rocks,
most of which have a chemical index of alteration (CIA) value of ~ 50. This lab considers the
geochemical and mineralogic changes when such rocks are exposed to acidic solutions in the
weathering environment by calculating the CIA values for 7 real rocks from Australia. After
erosion of the profile, this weathered material then becomes clastic sediment.
*****************************************************************************
Read all of these instructions carefully. There are questions and problems along the way
that need to be answered.
??? = ?????
----------------

(????? + ??? ∗ + ???? + ???) × ???

Complete data sets through modern weathering profiles
are relatively uncommon still, and to my knowledge this is the best of all available profiles.
For samples 1, 6, 8, 9, 10, 13, 15 you need to do the following things:
1) Calculate CIA (remember to use molecular proportions) and give me the coordinates for CN
and K (remember A = CIA). Note that in this exercise no value for CO2 is given, thus the only
correction we have for CaO* is to subtract apatite following the equation: mol CaO* = mol
CaO - 10/3 mol P2O5. Also remember, when CaO* = a negative number, set CaO* = 0
IMPORTANT keep this in mind: A + CN + K = 100.00 This is a rule.

1) A = CIA ______________ CN ______________ K ______________
6) A = CIA ______________ CN ______________ K ______________
8) A = CIA ______________ CN ______________ K ______________
9) A = CIA ______________ CN ______________ K ______________
10) A = CIA _____________ CN ______________ K ______________
13) A = CIA _____________ CN ______________ K ______________
15) A = CIA _____________ CN ______________ K ______________

Transcribed Image Text:Sedimentology Homework 1: CIA and Weathering Profiles The purpose of this lab is to review the mineralogy and geochemistry of weathering profiles developed on igneous and meta-igneous rocks. Weathering profiles are very important in the study of sedimentary rocks because when profiles are eroded by stream systems, clay minerals are separated from residual sand-sized particles. This separation of sands from muds by hydrodynamic processes creates the sediments and sedimentary rocks we are accustomed to seeing: sandstone, shale, conglomerate, etc. Chemical weathering plays a crucial role in the alteration of major-element geochemistry and mineralogy of siliciclastic sediments. Most of Earth's exposed crust is unweathered plutonic rocks, most of which have a chemical index of alteration (CIA) value of ~ 50. This lab considers the geochemical and mineralogic changes when such rocks are exposed to acidic solutions in the weathering environment by calculating the CIA values for 7 real rocks from Australia. After erosion of the profile, this weathered material then becomes clastic sediment. Read all of these instructions carefully. There are questions and problems along the way that need to be answered. CIA= Al₂O3 (Al₂O3 + Cao + Na₂O + K₂0) 1) A = CIA 6) A = CIA 8) A = CIA 9) A = CIA 10) A = CIA 13) A = CIA 15) A = CIA The following data set (attached at the end of the lab packet) comes from a modern weathering profile developed on bedrock in Australia. Complete data sets through modern weathering profiles are relatively uncommon still, and to my knowledge this is the best of all available profiles. For samples 1, 6, 8, 9, 10, 13, 15 you need to do the following things: 1) Calculate CIA (remember to use molecular proportions) and give me the coordinates for CN and K (remember A=CIA). Note that in this exercise no value for CO2 is given, thus the only correction we have for CaO* is to subtract apatite following the equation: mol CaO* = mol CaO - 10/3 mol P2O5. Also remember, when CaO* = a negative number, set CaO* = 0 IMPORTANT keep this in mind: A + CN+K=100.00 This is a rule. CN 3 3 3 3 3 3 CN CN CN CN CN CN K K K K x 100 K K