Bridgmanite may have held as much water as is present in today's oceans?

Question

BlackTom AI · Accepted Answer

Bridgmanite, the dominant mineral of the lower mantle (Mg,Fe)SiO3 in a perovskite structure, can incorporate hydrogen as hydroxyl defects within its crystal lattice. High-pressure, high-temperature experiments and theoretical work show bridgmanite can dissolve hydrogen at the level of hundreds to over a thousand parts per million (ppm) by weight under lower-mantle conditions, so it is plausible that it could store an amount of water comparable to Earth’s surface oceans.

Relevant concepts:
- Nominally anhydrous minerals (NAMs) can host water as OH defects even though they lack free H2O.
- The lower mantle is compositionally dominated by bridgmanite, so even small H concentrations per unit mass can sum to a large total reservoir.
- Ocean mass and mantle mass allow a simple mass-balance check to test plausibility.

Step-by-step reasoning and calculation:
1. Mass of Earth’s oceans ≈ 1.4 × 10^21 kg.
2. Mass of the whole mantle ≈ 4.0 × 10^24 kg; bridgmanite constitutes roughly ~70% of the mantle by mass → bridgmanite mass ≈ 0.70 × 4.0×10^24 kg = 2.8 × 10^24 kg.
3. Required bridgmanite water concentration to match ocean mass = (ocean mass) / (bridgmanite mass) = (1.4×10^21) / (2.8×10^24) = 5.0×10^-4 by mass = 0.05% = 500 ppm.
4. Laboratory and theoretical estimates show bridgmanite solubilities of order hundreds to >1,000 ppm H2O under lower-mantle pressures and temperatures, so a ~500 ppm average is within experimentally demonstrated ranges.

Why the correct answer is True:
Because bridgmanite comprises a very large mass fraction of the lower mantle, even modest H2O solubility (hundreds of ppm) integrates to a global reservoir comparable to the oceans. Experimental and seismological evidence (and analogous findings for transition-zone minerals like ringwoodite) support this possibility, so the statement that bridgmanite may have held as much water as today’s oceans is well founded.

Why “False” would be incorrect:
False would deny the experimental/theoretical and mass-balance plausibility. Although uncertainties remain about exact amounts and distribution, current data make the statement plausible rather than implausible.

Conclusion: The correct answer is True, matching the provided answer.

Bridgmanite may have held as much water as is present in today's oceans?判断题

类似问题

Bridgmanite was initially considered to hold little water. Recent research has changed this view. What is the important factor that allows Bridgmanite to hold more water than previously thought?

Which answer choice explains why furanoses and pyranoses can be reduced by sodium borohydride despite having no carbonyl functional groups.

Which of the following statements describes a glycoside?

Which of the following structures represents chitin?

In solution, glucose exists in

According to Xenophanes, what should be avoided at a symposium?

What is "kottabos"?

Why are there so many naked figures in vase iconography?

更多留学生实用工具

智能学习助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单