Quantifying tectonic exhumation in an extensional orogen with thermochronology: examples from the southern Basin and Range Province
Quantifying tectonic exhumation in an extensional orogen with thermochronology: examples from the southern Basin and Range Province
复制标题
用热年代学量化伸展造山带的构造折返：来自南部盆地和山脉省的例子
DOI：
10.1144/gsl.sp.1999.154.01.16
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发表时间：
1999
期刊：
影响因子：
--
通讯作者：
B. John
中科院分区：
文献类型：
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作者：
D. Foster;B. John
摘要科罗拉多河伸展走廊是一个大规模地壳衰减区，综合热年代学技术揭示了伸展和折返过程。走廊变质核杂岩中黑云母和钾长石的40Ar-39Ar年龄以及变质核杂岩中的锆石和磷灰石裂变径迹年龄在滑脱断裂的位移方向上一致年轻。快速伸展的开始是由年龄-闭合温度曲线得出的冷却速率和下盘年龄-距离梯度的斜率在约22-21 Ma的突然变化表示的。对于低温温度计时仪，斜率为3-8公里Ma−1的线性年龄-距离趋势给出了滑脱断层的时间平均位移速率。在已知倾角的情况下，跨厚倾斜上盘断块的矿物年龄梯度显示了古温度梯度。南部盆地和山脉省倾斜地块的伸展前温度梯度分别为约20-25°C KM−1、17°±5°C KM−1和约20-24°C KM−1。切梅韦拆离断层下盘的温度年代学数据显示，在伸展开始时，在已知的滑动方向上，温度从≤200°上升到350-400°C，外露距离为23公里。温度的逐渐升高限制了车梅韦拆离断层在脆性上地壳内具有约15-30°的原始倾角。
Abstract The Colorado River extensional corridor is a region of large-scale crustal attenuation, where the integration of thermochronological techniques illuminates processes of extension and exhumation. Biotite and K-feldspar 40Ar-39Ar, and zircon and apatite fission-track ages from metamorphic core complexes in the corridor consistently young in the displacement directions of detachment faults. The onset of rapid extension is denoted by an abrupt change, at c. 22–21 Ma, in cooling rate derived from age-closure temperature plots, and in slope of age-distance gradients in footwalls. Linear age-distance trends with slopes of c. 3–8 km Ma−1, for low-temperature thermochronometers, give time-averaged displacement rates on detachment faults. Gradients of mineral age across thick tilted hanging wall fault blocks reveal palaeotemperature gradients when the angle of tilting is known. Pre-extensional thermal gradients for tilted blocks in the southern Basin and Range province were c. 20–25°C km−1, 17° ± 5°C km−1, and c. 20–24°C km−1. Thermochronological data from the footwall of the Chemehuevi detachment fault reveal a trend of increasing temperature, in the known slip direction, from ≤200° to 350–400°C over an exposed distance of 23 km, at the onset of extension. The gradual increase in temperature constrains the Chemehuevi detachment fault to have had an original dip of c. 15–30°, within the brittle upper crust.