Light- and heavy-mineral diagenesis in Cambrian Sandstones of Michigan's Upper Peninsula
Sandstones of the Cambrian Munising Formation have a complex history of postdepositional alteration, including primary porosity reduction and intrastratal framework grain dissolution leading to secondary porosity formation. Primary porosity loss by carbonatization is evident in calcite- and dolomite-cemented samples. Feldspar overgrowths on detrital potassium feldspars effectively reduce primary pore space in 5-10% of the samples. Similarly, multiple generations of quartz overgrowths, distinguished by opaque inclusion rings, reduce porosity further. Authigenic pore-filling clays occur in more lithic-fragment-rich sands. Cemented samples clearly show that secondary porosity is associated with diagenetic alterations of feldspar and garnet. Feldspar dissolution occurs in detrital feldspar cores and as slightly corroded grain boundaries. Intrastratal dissolution of garnet is also evident. Thin sections show oversized pores associated with the garnet, and grain mounts show delicate imbricate wedge marks on garnet surfaces. Calcite also occurs as a fracture filling in, and replacement mineral on, garnet. Other heavy minerals (zircon and tourmaline) appear unaffected by diagenesis. The textural relationships of garnet dissolution vary with respect to the formation of early calcite and late dolomitic cements. The association between garnet and other diagenetic events constrains the chemistry of the intrastratal solutions, which affected garnet and formed overgrowths on feldspar and quartz.
- Research Organization:
- Michigan State Univ., East Lansing
- OSTI ID:
- 7041607
- Report Number(s):
- CONF-8610158-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Vol. 70:8; ISSN AAPGB
- Country of Publication:
- United States
- Language:
- English
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