The Potential for Diamond-Bearing Kimberlite in Northern ...

1 GEOLOGICAL SURVEY CIRCULAR 842 The Potential for Diamond-Bearing Kimberlite in Northern michigan and Wisconsin Prepared in cooperation with the Geological Survey Division, michigan Department of Natural Resources The Potential for Diamond-Bearing Kimberlite in Northern michigan and Wisconsin By W. F. Cannon and M. G. Mudrey, Jr. GEOLOGICAL SURVEY CIRCULAR 842 Prepared in cooperation with the Geological Survey Division, michigan Department of Natural Resources Description of a Kimberlite pipe and possible cryptovolcanic structures and a discussion of the possibility that kimberlites in Wisconsin and michigan might be the source for drift diamonds in Wisconsin Washington 1981 United States Department of the Interior JAMES G. WATT, Secretary Geological Survey Doyle G. Frederick, Acting Director Library of Congress catalog-card No. 81-600130 Free on application to Distribution Branch, Text Products Section, Geological Survey, 604 South Pickett Street, Alexandria, VA 22304 Abstract ---------------------------------------I ntroduction _____ _ diamond discoveries in Wisconsin ------------------Eagle, Waukesha County----------------------Plum Creek, Pierce County _____ _ Saukville, Ozaukee County _____ _ Kohlsville, Washington County (Theresa diamond ) __ Oregon, Dane County -------------------------Burlington, Racine County ---------------------Collins, Manitowoc County ---------------------Why no finds since 1913?

2 --------------------------The Lake Ellen Kimberlite -------------------------CONTENTS Page 1 Possible cryptovolcanic structures _____ _ 1 Glover Bluff structure -------------------------1 Structures near Pelkie, michigan _____ _ 1 Limestone Mountain-----------------------3 Sherman Hill -----------------------------4 Areas of disturbed Jacobsville Sandstone _____ _ 4 Brule River outlier ---------------------------4 Possible relationship between cryptovolcanic struc-4 tures and Kimberlite -----------~----------------4 Do Wisconsin drift diamonds have a local source _____ _ 4 Exploration for Kimberlite _____ _ 5 References cited --------------------------------ILLUSTRA TIONS Page 7 7 9 9 10 10 10 10 11 14 14 Page FIGURE 1. Index and location map of Wisconsin and Northern michigan ---------------------------------------- --2 2. Photograph of the Saukville and Burlington diamonds-------------------------------- ---------------3 3.

3 Magnetic map of the Lake Ellen Kimberlite area------------------------------------ ----------------6 4. Magnetic and gravity maps of the Glover Bluff disturbed area------------------------------------ -----8 5. Geologic map of the Pelkie, michigan , area------------------------------------ ---------------------9 6. Idealized cross section of a Kimberlite pipe------------------------------------ ---------------------11 7. Map of area and magnetic and gravity profiles across the Lake Ellen Kimberlite ---------------------------13 III The Potential for Diamond-Bearing Kimberlite in Northern michigan and Wisconsin By W. F. Cannon and Mudrey, ABSTRACT Between 1876 and 1913, diamonds were found in at least seven localities in southern and central Wisconsin. All were found in Pleistocene glacial deposits or Holocene river gravel. The bedrock Kimberlite source for the diamonds is unknown but has been presumed to be in Northern Canada, the only area north of Wisconsin previously known to contain kimberlites.

4 Recently, a Kimberlite pipe, here named the Lake Ellen kimber-lite, has been found in Iron County, michigan . That find sug-gests the possibility that drift diamonds in Wisconsin have come from a more local source--kimberlites in Northern michigan and Wisconsin. The Lake Ellen Kimberlite is very poorly exposed, but a strong positive magnetic anomaly indicates that it is roughly cir-cular in plan and about 200m in diameter. Although the kimber-lite is entirely surrounded by Precambrian rocks, it contains abundant inclusions of fossiliferous dolomite, probably from the Ordovician Black River Group that overlay the area when the Kimberlite was intruded. The post-Ordovician age of the Kimberlite leads us to suspect that other possible cryptovolcanic structures in Paleozoic rocks in the region were formed over Kimberlite pipes that are not yet exposed by erosion. Such struc-tures include Limestone Mountain and Sherman Hill, in Houghton and Baraga Counties, michigan ; Glover Bluff, in Mar-quette County, Wisconsin; and possibly an area along the Brule River south of Iron River, michigan .

5 No diamonds are known in the Lake Ellen Kimberlite , but it has not been adequately sampled. The cryptovolcanic structures could not be the source of the drift diamonds in Wisconsin be-cause even if the structures are caused by kimberlites, those kimberlites have not yet been exposed by erosion. Elsewhere in the world, Kimberlite is seldom found as a single isolated body; clusters of bodies are more common, and the presence of one Kimberlite implies that others may exist nearby. The discovery of additional kimberlites may be very difficult because of the extensive cover of glacial drift and the typical small size of Kimberlite bodies. If all are magnetic, they might be found by detailed aeromagnetic surveys. However, the mag-netism of the Lake Ellen Kimberlite appears to be caused by sec-ondary magnetite formed during serpentinization of olivine, so an unserpentinized Kimberlite may not be strongly magnetic.

6 We suggest that one or more Diamond-Bearing kimberlites may exist in Northern michigan or Wisconsin, but the discovery of such bodies is unlikely unless a very thorough search is under-taken. 1 Wisconsin Geological and Natural History Survey. 1 INTRODUCTION At least seven diamond discoveries were made in Wisconsin between 1876 and 1913. All diamonds were found in Pleistocene glacial deposits or Holo-cene river gravel. The diamonds must have been eroded from one or more Kimberlite bodies because Kimberlite is the only primary bedrock source of diamonds. It has generally been presumed that drift diamonds in Wisconsin were carried to their discovery sites by glaciers that eroded them from the nearest known kimberlites in Northern On-tario, 800 km (kilometers) (500 miles) or more away. In this paper, we describe a newly discovered Kimberlite in Northern michigan and suggest several other areas where kimberlites may exist in the subsurface.

7 We discuss the possibility that drift diamonds in Wisconsin were eroded from kimber-lites in Wisconsin or michigan . diamond DISCOVERIES IN WISCONSIN Verified discoveries of diamonds have been made at seven localities in Wisconsin (figs. 1, 2). Other diamonds have been reported, but they were prob-ably not from Wisconsin and are only briefly discussed in the following sections. EAGLE, WAUKESHA COUNTY The first documented diamond discovery in Wisconsin was made during the digging of a well in 1876 by Charles Wood, who was a tenant on the farm of Tom Devereaux near Eagle in southwestern Waukesha County (Hobbs, 1899; Vierthaler, 1958; Olson, 1953; Alden, 1918). This first important Wisconsin diamond discovery is recorded in the files of the Milwaukee County Cir-cuit Court and the Wisconsin Supreme Court. The digging passed through 10-15 m (meters) (33-44 0 0 100 MILES 100 KILOMETERS EXPLANATION o POSSIBLE CRYPTOVOLCANIC STRUCTURES 1.)

8 GLOVER BLUFF 2. STRUCTURES NEAR PELKIE (INCLUDES LIMESTONE MTN AND SHERMAN HILL) 3. BRULE RIVER OUTLIER \t DIRECTION OF ICE MOVEMENT NEAR diamond LOCALITIES + DRIFT diamond LOCALITIES 1. EAGLE, WAUKESHA COUNTY 2. PLUM CREEK, PIERCE COUNTY 3. SAUKVILLE, OZAUKEE COUNTY 4. KOHLSVILLE, WASHINGTON COUNTY 5. OREGON, DANE COUNTY 6. BURLINGTON, RACINE COUNTY 7. COLLINS, MANITOWOC COUNTY ___ EXTENT OF ICE LOBES a. GREEN BAY LOBE b. LAKE michigan LOBE FIGURE showing the location of diamond discovery sites, marginal moraines of major ice lobes and direction of ice movement, possible cryptovolcanic structures, and the Lake Ellen Kimberlite . 2 ~---12mm---~ -FIGURE The Saukville diamond (left) and Burlington diamond (right). ft) of clay and then through loose gravel of approx-imately 5 m (16ft), when a 2-m (7-ft) layer of a hard yellow material was penetrated. A hard stone of unknown identity was recovered. Clarissa Wood took this peculiar pebble to Col.

9 Samuel B. Boyn-ton, a jeweler in Milwaukee. Boynton identified the stone as "topaz" and purchased it for $ Once the true identity of the diamond was disclosed, Clarissa offered to buy the diamond back, first for $ and later for $ Boynton refused, and Mrs. Wood sued. The Supreme Court ruled that the stone was Boynton's because he had believed it was topaz when he bought it. He later sold the stone to Tiffany & Company of New York for $850. He had offered the stone to the State of Wisconsin for $1,000, but his offer was declined. The crystal, originally known as the Waukesha diamond and later as the Eagle diamond , is a warm yellow color and weighs carats. Boynton formed a diamond -mining company and later, in 1883, claimed to have discovered more diamonds, along with other precious and semiprecious stones , according to Silvers (1978) writing in a recent issue of The Milwaukee Journal. 3 A mining boom resulted.

10 G. F. Kunz, a noted gem-nologist, visited the area and noted that the newly found stones differed in size, color, and number of crystal faces from the original find. He identified the new stones to be of African origin, and the bot-tom fell out of the great Eagle diamond rush. J. P . Morgan, the late 19th century financier, purchased the Eagle diamond from Tiffany's and ultimately donated the gem to the American Museum of Natural History in New York City. The stone was on public display at the Museum until the evening of October 29, 1964, when the Museum was broken into and the Eagle diamond and other gems stolen. On February 8, 1965, Jack Roland Murphy, a Florida beach boy, also known as "Murph the Surf," and two colleagues, admitted the theft, but the stone was not recovered. PLUM CREEK, PIERCE COUNTY In the period 1880-1887, G. H. Nichols and two colleagues prospected for gold along Plum Creek in Pierce County.