Bilingual edition: English is preserved and Chinese follows each unit. Terminology uses the confirmed v20260916 glossary; automated semantic review remains traceable.
中英双语版：英文原文完整保留，中文紧随对应单元；术语采用 v20260916 确认表，自动语义审校结果可追溯。

Rubidium-Strontium Isochrons

铷-锶等时线
Click on the illustration to step through the discussion.

Rubidium-strontium isochrons can be used to calculate the last time of complete melting of a rock. The complete melting of the rock is a necessary condition, because that is what accomplishes the equilibrium of the isotopes of strontium. The isotopes of an element are chemically identical, and any chemical process will treat them identically. That's why we know the ratio of the strontium isotopes in the melt is a horizontal straight line in the illustration above. The isotope 86Sr is non-radiogenic in origin and does not change, but 87Sr is produced by the radioactive decay of 87Rb. There is no way of anticipating what the 87Sr is at the time of melt, but if there is 87Rb present then it will increase with time as the rubidium isotope decays. That is what makes this a useful clock.

铷-锶同位素比可用于计算岩石完全熔融的最后时间。岩石的完全熔融是必要条件，因为这是使锶同位素达到平衡的关键。同一种元素的同位素在化学上是相同的，任何化学过程都会一视同仁地对待它们。这就是为什么在图中熔融物中锶同位素的比例是一条水平直线。86Sr的来源是非放射性的，不会发生变化，而87Sr是由87Rb的放射性衰变产生的。无法预测熔融时刻时87Sr的含量，但如果存在87Rb，则会随着时间推移而增加，因为铷同位素会衰变并产生87Sr。正是这一点使这种钟表成为有用的工具。
Clocks in the Rocks
岩石中的时钟
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Rubidium-Strontium Isochrons

铷-锶等时线
Click on the illustration to step through the discussion.

Rubidium-strontium isochrons will be formed at any time after crystallization of a rock provided the initial conditions are met. Different minerals which make up the rock will in general include different amounts of rubidium (87Rb) in their structures, and those which have more rubidium at the time of crystallization will have more radioactive decays and gain more of the daughter product 87Sr. The precise nature of the radioactive decay process predicts that all the minerals should lie along a straight line, an isochron. The longer the time interval, the more the decay and the steeper the slope of the isochron line.

在岩石结晶后任何时间，只要初始条件得到满足，就会形成铷-锶同位素体系。组成岩石的不同矿物通常含有不同量的铷（87Rb），在结晶时含有更多铷的矿物将经历更多的放射性衰变，并产生更多的子产物87Sr。放射性衰变过程的精确性质预测所有矿物应位于一条直线上，即同位素体系。时间越长，衰变越多，同位素体系线的斜率也越陡。
Clocks in the Rocks
岩石中的时钟
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Rubidium-Strontium Isochrons

铷-锶等时线
Click on the illustration to step through the discussion.

Rubidium-strontium isochrons can be used to calculate the last time of complete melting of a rock. The slope of the isochron line gives a measurement of the time since the last complete melting of the rock. It also gives the initial concentrations of strontium at the time of melting by projecting the isochron line to the point of zero 87Rb concentration. If the strontium isotope ratios for the various minerals do not form a straight line, then the assumptions of the analysis are invalid. Perhaps some things can be learned from the data, but it does not give an unambiguous date since melting.

Clocks in the Rocks
岩石中的时钟
铷-锶等时线可以用来计算岩石完全熔融的最后时间。等时线的斜率给出了岩石最后完全熔融以来的时间测量值。它还能通过将等时线投影到零87Rb浓度点来确定熔融时的锶初始浓度。如果各种矿物的锶同位素比值不形成一条直线，则分析的假设是无效的。也许可以从数据中获得一些信息，但并不能给出一个明确的时间，因为熔融过程可能不完全。
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Rubidium-Strontium Isochrons

铷-锶等时线

Rubidium-strontium isochrons are not fool-proof, but they are to some extent self-checking. Only to the extent that the different mineral components within a rock lie along a straight isochron line can you have confidence in the measured time since the last complete melt. If the rock did not completely melt so that the initial assumptions are not met, then there will be minerals for which the strontium isotope ratio does not lie along the line. This is not uncommon. There are minerals like zircon which have a high melting point and may not melt when the other minerals in the rock do. The Rb-Sr isochron method is usually not applicable to recent lava flows on or near the surface because the temperatures involved are often not high enough to produce complete melts.

铷-锶等时线并非万无一失，但它们在一定程度上具有自我检验的特性。只有当岩石中的不同矿物成分沿着一条直线排列时，才能对自最后一次完全熔融以来的时间测量有把握。如果岩石并未完全熔融，使得初始假设不成立，那么就会有某些矿物的锶同位素比值不沿着这条直线。这种情况并不罕见。例如，锆石等矿物具有较高的熔点，可能在岩石中其他矿物熔融时仍未熔化。因此，Rb-Sr等时线法通常不适用于地表附近或地表上的近期火山熔岩流，因为所涉及的温度通常不足以产生完全的熔融。
Clocks in the Rocks
岩石中的时钟
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