کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4689841 1636096 2012 18 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Intrinsic versus extrinsic controls on the development of calcite dendrite bushes, Shuzhishi Spring, Rehai geothermal area, Tengchong, Yunnan Province, China
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات فرآیندهای سطح زمین
پیش نمایش صفحه اول مقاله
Intrinsic versus extrinsic controls on the development of calcite dendrite bushes, Shuzhishi Spring, Rehai geothermal area, Tengchong, Yunnan Province, China
چکیده انگلیسی

In the Rehai geothermal area, located near Tengchong, there is an old succession of crystalline calcite that formed from a spring that is no longer active. The thin-bedded succession, exposed on the south bank of Zaotang River, is formed of three-dimensional dendrite bushes that are up to 6 cm high and 3 cm in diameter with multiple levels of branching. Bedding is defined by color, which ranges from white to gray to almost black and locally accentuated by differential weathering that highlights the branching motif of the dendrites. The succession developed through repeated tripartite growth cycles that involved: Phase I that was characterized by rapid vertical growth of the dendrite bushes with ever-increasing branching; Phase II that developed once growth of the dendrites had almost or totally ceased, and involved an initial phase of etching that was followed by the precipitation of various secondary minerals (sheet calcite, trigonal calcite crystals, hexagonal calcite crystals, hexagonal plates formed of Ca and P, Mn precipitates, Si–Mg reticulate coatings, opal-CT lepispheres) on the branches of the calcite dendrites, and Phase III that involved deposition of detrital quartz, feldspar, clay, and calcite on top of the dendrite bushes. The tripartite growth cycle is attributed primarily to aperiodic cycles in the CO2 content of the spring water that was controlled by subsurface igneous activity rather than climatic controls. High CO2 coupled with rapid CO2 degassing triggered growth of the dendrite bushes. As CO2 levels waned, saturation levels in the spring water decreased and calcite dendrite growth ceased and precipitation of the secondary minerals took place, possibly in the microcosms of microbial mats. Deposition of the detrital sediment was probably related to surface runoff that was triggered by periods of high rainfall. Critically, this study shows that intrinsic factors rather than extrinsic factors (e.g., climate) were the prime control on the development of the tripartite growth cycle.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Sedimentary Geology - Volumes 249–250, 1 April 2012, Pages 45–62
نویسندگان
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