Final answer:
Using the 25/75 ratio for 235U/207Pb isotopes found in the zircon mineral from Intrusion H suggests that the intrusion is approximately 0.704 billion years old, as this ratio indicates that one half-life period of the 235U has passed.
Step-by-step explanation:
To calculate the absolute age of an intrusion, such as Intrusion H, one would typically use radiometric dating techniques. When analyzing zircon minerals from Intrusion H, if a ratio of 25/75 for 235U/207Pb is found, this indicates that three-quarters of the original 235U has decayed into 207Pb. It is necessary to know the half-life of 235U to determine the absolute age in years, which is 0.704 billion years.
Using the ratio and the half-life, we can use the following logic: If 75% of the uranium has decayed, this indicates that Intrusion H has gone through roughly one half-life period.
Therefore, the approximate age of Intrusion H would be around 0.704 billion years, or 704 million years. This aligns with the known applications of uranium-lead dating, which can give ages ranging from about 4.5 billion to 5 million years. Please note that for exact calculations, a more detailed understanding of the decay series and mathematical formula would be required.