Geology and Geophysics
2025 · Paper 1
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Complete GATE GG-1 2025 Paper 1 overview, original pages and practice · Timed previous-paper practice
Questions 64–65 of 65. Imported answers require review unless explicitly marked reviewed.
Question 64
Open questionGGNAT2 marksNeeds review
Th and
Ra are intermediate nuclides in the decay series of
U to
Pb. The half-lives of
U,
Th, and
Ra are 4.47 billion years, 75,000 years, and 1600 years, respectively. At secular equilibrium, when activities are equal, 10 billion atoms of
U are present. The number of atoms of
Ra present at equilibrium is __________. (Answer in integer)Log in to check the answer
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Open questionGGNAT2 marksNeeds review
The following table provides the mineral chemistry of a garnet. All oxides are in weight percentage and cations in atoms per formula unit. Total oxygen is taken as 12 based on the ideal garnet formula. Consider Fe as Fe
and Fe
= 0. The X
of this garnet is __________.Oxides | Wt % | Cations | apfu |
|---|---|---|---|
SiO | 39.51 | Si | 2.998 |
TiO | 0.05 | Ti | 0.003 |
Al O | 22.35 | Al | 1.999 |
Cr O | 0.00 | Cr | 0.000 |
FeO | 26.25 | Fe | 1.66 |
MnO | 0.00 | Mn | 0.000 |
MgO | 10.80 | Mg | 1.21 |
CaO | 1.40 | Ca | 0.114 |
Na O | 0.00 | Na | 0.000 |
K O | 0.00 | K | 0.000 |
Total | 100.36 | Total cation | 8.01 |
(Round off to three decimal places and do not multiply by hundred)
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