Question

The most common mineral used in U-Pb radiometric dating is \(\underline{\hspace{1cm}}\).

• A. Biotite
• B. Zircon
• C. Hornblende
• D. Quartz

Hint:

When you think of U-Pb dating, the primary mineral to remember is Zircon. Its properties of incorporating uranium but rejecting lead, combined with its exceptional durability, make it the gold standard for geochronology.

Answer 1

The Correct Option is B

Step 1: Understand the requirements for a good mineral for U-Pb dating.
An ideal mineral for Uranium-Lead dating should readily incorporate uranium (U) into its crystal structure upon formation but strongly reject lead (Pb). This ensures that any lead found within the mineral is almost entirely the product of the radioactive decay of uranium, not from initial contamination. The mineral should also be highly resistant to weathering and metamorphism.

Step 2: Evaluate the options.
(A), (C): Biotite and Hornblende can be used for some radiometric dating (like K-Ar), but they are not ideal for U-Pb because they can lose lead and are less resilient. (B) Zircon (ZrSiO\(_4\)) is the ideal mineral for U-Pb dating. It readily accepts uranium but excludes lead during crystallization and is extremely durable, surviving multiple geological cycles. This makes it an excellent time capsule for radiometric dating. (D) Quartz (SiO\(_2\)) does not incorporate significant amounts of uranium or other radioactive elements into its structure, making it unsuitable for this dating method.